Assassin bug nymph bite


Assassin bug

Predatory behaviour

Assassin bugs display a range of predatory behaviours and prey on a variety of other insects. The black corsair (Melanolestes picipes), a black-coloured insect about 13 to 20 mm (0.5 to 0.8 inch) long and usually found under stones and bark, can inflict painful bites on humans. The masked hunter (or masked bedbug hunter; Reduvius personatus), when threatened, will also bite humans, causing pain and localized swelling. The masked hunter is widely known for its ability to camouflage itself as a ball of dust during the immature stages, when the body, legs, and antennae become covered with sticky hairs that catch pieces of lint and dust. The brownish black adult, roughly 15 to 22 mm (0.6 to 0.87 inch) long, is commonly found preying on insects, such as bedbugs and flies, in houses. Though originally a central European species, the masked hunter has spread throughout parts of the United States and Canada since its accidental introduction.

Some of the best-known assassin bugs are the members of subfamily Triatominae, commonly known as triatomine bugs or kissing bugs. Some species of triatomine bugs—particularly members of the genera Panstrongylus, Rhodnius, and Triatoma—are carriers of the protozoan parasite Trypanosoma cruzi, which causes Chagas disease. Triatomines can survive in a variety of habitats, including underneath rocks and bark, inside the nests of other animals, and inside houses. The Old World species Triatoma rubrofasciata, for example, has been found living in houses as well as in chicken coops and other structures in North America. Rhodnius prolixus is a major vector of Chagas disease in South and Central America. It also has been much used in insect physiology and disease research.

Chagas disease vector: Triatoma infestansTriatoma infestans, a vector for Chagas disease.World Health Organization/CDC Get exclusive access to content from our 1768 First Edition with your subscription. Subscribe today

The genus Apiomerus, which contains species known commonly as bee assassins or bee killers, is among the largest genera in family Reduviidae. Species of Apiomerus frequent flowering plants, where they coat their legs with sticky plant resins and wait for their prey. The sticky resins allow the assassins to readily capture other insects, particularly bees. Plant resins also appear to play a role in maternal care among certain Apiomerus species.

The wheel bug (Arilus cristatus) is recognized by the notched semicircular crest on the top of the thorax. The adult is brown to gray and large, about 25 to 36 mm (1 to 1.5 inches); the nymph is red with black marks. Wheel bugs occur in North America, are predaceous on other insects, and have a painful bite if handled. The venomous saliva is pumped into a victim through a channel in the wheel bug’s beak. The digested body fluids of the prey are then pumped into the wheel bug’s stomach through another channel in the beak.

  • wheel bugWheel bug (Arilus cristatus).Encyclopædia Britannica, Inc.
  • Wheel bug (Arilus cristatus)Richard Parker—The National Audubon Society Collection/Photo Researchers

The thread-legged bug Emesaya brevipennis, of which there are three subspecies, is about 33 to 37 mm (1.3 to 1.5 inches) long and is usually found on trees or in old buildings. It has long threadlike middle and hind legs, while the shorter, thicker front legs are modified into viselike grasping organs. E. brevipennis occurs in North America.

The thread-legged bug Stenolemus bituberus, which is native to Australia, preys on web-building spiders. It uses one of two different predatory strategies: stalking, in which it approaches its prey slowly and strikes when within range, or luring, in which it plucks the silk threads of the spider’s web with its forelegs, which mimics the behaviour of an insect trapped in the web and thereby attracts the resident spider to within striking distance. The luring predatory behaviour displayed by S. bituberus represents a form of aggressive mimicry.

Several members of the subfamily Holoptilinae, commonly called feather-legged bugs, possess a specialized outgrowth on the abdomen known as a trichome. A secretion released from the trichome attracts ants, which lick the substance and become paralyzed. The feather-legged bug then pierces the ant with its beak and sucks out the body fluids. The behaviour was first reported in 1911 in the Southeast Asian species Ptilocerus ochraceus. It has since been observed among other Holoptilinae species, including Ptilocnemus femoralis and Ptilocnemus lemur.

The species Platymeris rhadamanthus “spits” saliva in reaction to certain disturbances. Saliva is ejected toward an attacker and can travel as far as 30 cm (12 inches). It contains lytic substances, capable of externally digesting the bug’s victims.

The predatory ambush bugs, subfamily Phymatinae, are known for hiding on vegetation and suddenly attacking their prey, capturing their victims with their greatly enlarged fore femurs.

Assassin bugs are a large group of insects in the family Reduviidae. There are well over 155 different species of assassin bugs, and they are all joined by one specific characteristic: these insects are equipped with a curved, pointed mouthpart known as a “proboscis.” Their proboscis’ are used to stab and kill prey, and can be used to defend themselves from predators as well. Read on to learn about the assassin bug.

Description of the Assassin Bug

There is quite a wide variety of species, which come in a number of shapes and sizes. They can range anywhere from 0.16 – 1.57 in. long. While a few are demur in color, most are brightly colored, or have flashy accents. Common colors include brown, black, red, orange, and green. Their mouthparts are tubular, segmented, and pointed.

Interesting Facts About the Assassin Bug

Though these insects appear relatively harmless, beware handling them! Most people are aware of bees, wasps, and other stinging creatures, but ignorant of the potential pain assassin bugs can inflict.

  • Handle With Caution – If these bugs feel threatened, they implement their long proboscis. They can deliver a surprisingly painful jab, and some species will also inject venom or digestive juices. Though this bite is not medically dangerous, this can be a painful encounter.
  • Utility Jab – The sharpened proboscis is not present just to terrify women and children. Rather, they use their proboscis to hold up their namesake. These predatory insects will stab their prey to injure or kill it before consuming it.
  • Insect Soup – After their prey has been immobilized or killed these insects are faced with a problem. Their only mouthparts are the long proboscis used to kill prey. Instead of chewing and eating their food, they inject digestive juices into it and slurp it up through their proboscis.
  • Other Dangers – While their bite is painful, but harmless to humans, they should still be avoided. Some species are known to spread Chagas disease, which can cause heart failure and damage to major organs. Though there is a very slim chance of this occurring, it’s better to be safe than sorry.

Habitat of the Assassin Bug

These bugs live in a large number of different habitats. They can be found in rainforests, rocky areas, inside animal nests, in woodpiles, gardens, chicken coops, and more. With such a wide variety of species there are virtually endless habitats that are occupied by these bugs.

Distribution of the Assassin Bug

The vast majority of species are found in North America, but these creatures can be found nearly worldwide. They are found in Europe, parts of Asia, Central America, South America, and Africa, as well. There are a wide variety of species, but the greatest species diversity occurs in North America.

Diet of the Assassin Bug

The predatory behavior of these insects is quite interesting. Instead of hunting and capturing small prey, these insects can consume creatures much larger than themselves. After stabbing the prey with their proboscis, they inject venom or digestive juices into the body of the prey. This can effectively kill prey much larger than the assassin bug. They feed primarily on insects, but a few insects are considered parasitic and feed on mammalian blood.

Assassin Bug and Human Interaction

For the most part these insects are harmless to humans, if a touch painful. A few species can actually be dangerous to humans, not from the bite itself but from the transmission of Chagas disease. This can sometimes be fatal to humans, and is spread when the insect bites. Other species can be quite beneficial by killing pests that could potentially harm crops, rainforests, and other protected habitats.


Assassin bugs have not been domesticated in any way.

Does the Assassin Bug Make a Good Pet

Because they can deliver a painful bite, and some species can transmit a potentially fatal disease, these creatures do not make good pets.

Assassin Bug Care

These creatures should always be kept hands-off to prevent painful bites. Only a few species are kept regularly in human care, including the white-spotted assassin. Because their eggs and offspring are very small, it is important to keep a very fine grade screen over the enclosure. Many species require high humidity, and plenty of woody hiding places like branches or bark. They can be fed roaches, waxworms, moths, grasshoppers, crickets, and other insects, but their diet should be varied.

Behavior of the Assassin Bug

These insects are surprisingly adept predators, and spend much of their time hunting for food. Social behavior depends heavily on the species, some are solitary, some live in groups, and some congregate in hiding places. The same goes for reproduction, some species reproduce singly, while other congregate in large groups.

Reproduction of the Assassin Bug

After breeding, females lay clumps of fertilized eggs, usually onto a leaf or stem of a plant. The baby bugs, called “nymphs,” look like tiny versions of the adults at birth. The nymphs are born without wings, and go through metamorphosis before reaching sexual maturity and gaining wings. The incubation time of eggs, and development time of nymphs, varies greatly between species.

Assassin Bug Identification – How Long Do Assassin Bug Eggs Take To Hatch

Beneficial insects are crucial to healthy gardens. The assassin bug is one such helpful insect. What do assassin bugs look like? Recognizing this garden predator as a good garden helper rather than a potentially scary threat to you puts a natural perspective on the normal cycle of life in your landscape. Assassin bug identification will also prevent some nasty and very painful bites that may occur accidentally.

What Do Assassin Bugs Look Like?

Assassin bugs occur in much of North America but also Central and South America, Europe, Africa and Asia. There are several species of the insect, all of which are natural ambush hunters that inject a toxin into prey which dissolves their soft tissues. These bites are fatal to their insect victims but may also cause allergic reactions in humans, resulting in painful itching and burning at the injection site.

Assassin bugs have several stages of life. Assassin bug eggs may be found in cracks, under rocks and in other sheltered locations. The tiny clusters of eggs hatch to become assassin bug nymphs, which are the larvae of the insect. Assassin bug nymphs are less than ½ inch

long, and are orange and black striped with an almost translucent base color.

The adult form of the insect may grow up to an inch in length. These have a 3-part body consisting of a head, thorax and abdomen. The head is cone shaped and sports a curved beak from which the insect injects its toxin. They also bear long antennae and six long legs. Assassin bug identification also notes that the insect is beige with black markings and folded wings perched on its back.

How Long Do Assassin Bugs Take to Hatch?

Assassin bug eggs are laid in summer, but how long do assassin bugs take to hatch? Eggs will hatch shortly after they are laid; however, it can take an entire year for nymphs to reach maturity. Young insects overwinter in bark, under logs and in crevasses. They are semi-dormant during the winter and will molt in spring, with their final adult form revealed in June.

That is a whole year from hatching, so only one generation of assassin bugs per year. The wingless nymphs grow and molt 4 times, and in some species 7 times, over the course of the year. Adult form is achieved once the insects have wings.

Assassin Bugs in Gardens

Assassin bugs inject a poison into their prey through their beak. This proboscis-like appendage delivers toxin into the vascular system and causes almost instant immobilization and simultaneous liquefaction of internal fluids. These fluids are sucked out of the prey. The prey is left behind as just a husk.

If you are unlucky enough to get an assassin bug bite, you will know it. The pain is quite sharp and intense. Most people who get bitten simply get a red bump with some accompanying itching once the pain fades. However, some people are actually allergic to the toxin and more intense experiences face these sensitive individuals.

The bug’s toxin is never fatal but it can cause increased pain, swelling, and itching that can last several days to a week. For this reason, assassin bug identification can help keep you out of the insect’s way while it does its beneficial work of ridding your garden of pesky insects.

Assassin Bug (Pselliopus spp.)

Rough handling can invite an intense and unforgettably painful ‘bite’ from the powerful fang of an Assassin Bug juvenile or adult.

The strong beak found on Assassin bugs is used to repeatedly, and violently, stab its prey to death, hence the name ‘assassin’. This insect can also inflict terribly painful bites on careless humans and may be best left observed and not handled. The long, pointy beak is kept tucked under the head when not in use and makes noise when moved back-and-forth. They do not feed on plants, but they hunt on them. They can be found on shrubs, ground cover, and garden plants as they search for insect prey. Assassin Bugs move quickly and nimbly, surprising their victims. Once a prey item is caught, Assassin bugs use their powerful front legs to hold the insect down while it is stabbed to death and body fluids are subsequently sucked out.
Adults have narrow heads and wider abdomens. Many are black with red or orange markings on them though some are brown. The sides of the abdomen are flared upward and may have a checkered pattern on them. A long fang hides under the head. Nymphs (juveniles) are smaller, though somewhat similar in appearance. They also tend to have abdomens that rise upward at the sides. They may lift the tip of the abdomen in the air when walking or resting, like their ‘butt’ is in the air. This posture mimics certain types of stinging insects when they are under threat and may be a defensive warning. The irony is that the real danger from Assassin Bugs originates at this insect’s front end.
Most of North America is home to some type of Assassin Bug. The Wheel Bug is a commonly seen member of the Assassin Bug family. Its red and black nymphs are often sighted crawling in large groups on branches during spring and summer. Because of their diet, they are a helpful aid in controlling unwanted insect populations in a garden.

46 Milkweed Assassin Bug Facts: Brutal Insect Executioners (Zelus longipes)

Looking to learn more about milkweed assassin bugs? You’re in the right place! These guys are pretty freaky, and we’ve got everything you want to know right here. So read on if you want to be amazed.

Table of Contents

46 Milkweed Assassin Bug Facts

With “assassin” right there in the name, you probably expect the milkweed assassin bug to be a ghastly murderer.

You’d be right.

Though they’re mostly harmless to humans, milkweed assassin bugs are brutal executioners when it comes to other bugs. They can wrestle down beetles and butterflies up to six times their size, and when they’re ready to eat, they inject a flesh-melting venom into their victims that literally liquefies their insides.

It’s pretty gross, right? But we’re just getting started. Keep reading these milkweed assassin bug facts to learn more about nature’s long-legged killing machines.

1. What is a milkweed assassin bug?

Milkweed assassin bugs are relatively common insects that are found around homes, gardens, farms and crop fields.

They can be quite helpful to local ecosystems, but they can also deliver painful bites when they’re feeling threatened. If you’ve noticed milkweed assassin bugs around your tomatoes, it’ll be up to you to decide whether or not their benefits outweigh their bites.

2. What does the milkweed assassin bug look like?

The milkweed assassin bug has a very distinctive appearance. As part of the “assassin” family, it has long, spindly legs and even larger and spindlier antennas. It also boasts a sucking mouthpiece that allows it to drink down its prey after liquefaction.

The most notable feature of the milkweed assassin bug, however, is its coloring. It has a bright reddish-orange body with black limbs, so it definitely stands out when it’s perched on a leaf.

If you take a closer look, you’ll also notice “wing pads” on its back. These aren’t true wings; they never mature past the beginning stages of development and they won’t support the milkweed in flight. But they’re more than just black spots!

3. How big is a milkweed assassin bug?

It depends on the gender of the bug. Males usually measure around 16.1 – 16.8 millimeters while females hover around 18.2 – 18.4 millimeters.

As you can see, males are smaller than females. Males also have rounder torsos while females are flatter or plate-like.

4. Why do milkweed assassin bugs have sticky legs?

They aren’t sticky all of the time! The legs of the milkweed assassin bug are covered in short, pointed hairs like sundew plants. These hairs are used as grips for a sticky resin that the bugs can produce from glands on their front legs.

They spread the resin around their limbs to create a sort of glue trap that can be used to catch and immobilize their prey.

5. How many types of assassin bugs are there?

There are more than 7,000 species of assassin bugs.

They belong to the reduviidae family, and they’re famous for their gruesome killing methods when they hunt. Some of them even feed exclusively on blood like a leech.

6. How can milkweed assassin bugs be distinguished from other types of assassin bugs?

Have you spotted some long-legged, leaf-crawling bugs in your garden? Are you wondering if they’re milkweeds or something else entirely? Here are a few ways to tell:

  • What do they look like? Assassin bugs can have drastically different appearances. For example, while the milkweed assassin bug has a bright, vivid color, the masked hunter assassin bug is brown-bodied to help it blend into sand and dirt.
  • How do they eat? If you catch them in the act of feeding, that can tell you a lot. Milkweed assassin bugs hold their victims close and use their suckers like vacuums, but other species like to crush their prey or consume them whole.
  • What do they eat? If they eat anything other than insects, they aren’t milkweeds. Milkweeds are notoriously uninterested in leaves, bark, bushes and other staples of bug diets.
  • Did they bite or sting you? Did they try to suck your blood? Milkweed assassin bugs are semi-afraid of humans, so they’ll only deliver a quick defensive bite and move on, but other species might be more aggressive. Do some research on their behavior to figure out which type of bug that you have on your property.

7. How did the milkweed assassin bug get its name?

Milkweed assassin bugs get their name from their resemblance to regular milkweed bugs (oncopeltus fasciatus).

Milkweeds have the same orange-and-black coloring, and they’re found in the same regions of Central and South America. It was probably inevitable that their long-legged cousins were named after them.

8. Are milkweed assassin bugs aggressive?

Yes and no. Milkweed assassin bugs are ambush predators with a swift execution style, so they can be quite aggressive when it comes to catching and killing their prey. They don’t live leisurely lives.

On the other hand, milkweed assassin bugs don’t pose a threat to humans. They bite, but that’s only if you disturb their territory. They won’t bother you if you don’t bother them.

In fact, unless they’re guarding their egg clusters, most milkweed bugs will scatter when you get too close. It’s hard to classify this kind of creature as “aggressive” since they’re so reactive instead of offensive.

9. Do milkweed assassin bugs bite?

Yes. Milkweed assassin bugs will bite humans when they’re feeling threatened.

Normally, they’ll use their beak-like sucker to puncture their prey and drink their insides. While they won’t liquify your insides, the exact kind of bite you receive will depend on the exact kind of circumstances.

10. Are milkweed assassin bugs harmful to humans?

Milkweed assassin bugs can deliver a painful bite thanks to the venom found in their saliva. It’s so powerful that it can literally melt the tissues and organs of other insects into liquid form.

Humans, on the other hand, are made of stronger stuff. You’ll feel a sting from the venom, and it might cause a painful lump under your skin for a few days, but that’s about it. It won’t have any long-term consequences for you. You aren’t an earthworm!

11. Are milkweed assassin bugs dangerous?

To other insects, milkweed assassin bugs are harbingers of doom. They’ll prey on anything and everything that lives in a garden or vineyard, and they can win fights against creatures much bigger than themselves.

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There’s a reason why milkweed assassin bugs have to hide before they strike. If they were out in the open, other bugs would flee from them as a matter of course.

12. Are milkweed assassin bugs bad for monarch butterflies?

Milkweed assassin bugs prey on caterpillars, so they aren’t great for monarch butterflies. However, they don’t target them any more than other species.

This is sometimes a point of confusion for people who expect milkweed assassin bugs to act like regular milkweed bugs: both milkweeds and monarchs live off the milkweed plant, so if resources are scarce, they can be in direct competition for the same food supply.

Milkweed assassin bugs, on the other hand, don’t care about milkweed plants at all. They were only named for their superficial resemblance to milkweed bugs.

13. What do milkweed assassin bugs do?

Milkweed assassin bugs aren’t always a nuisance. Some people will even breed or deliberately introduce them to their landscapes. They’re used for a very specific purpose: pest control.

You see, milkweed assassin bugs will eat pretty much any insect that they come across. They aren’t picky. Whether it’s a corn silk fly or a big, juicy beetle, they’ll make a meal out of anything that crawls into their path.

This makes them ideal for farmers who don’t want to resort to pesticides. Instead of spraying lots of chemicals in their fields, they can just introduce the milkweed assassin bug to the environment.

Milkweeds aren’t considered an invasive species, so they won’t harm anything. They won’t even munch on the fruits and veggies growing out of the ground. They’re only interested in other bugs.

14. Can milkweed assassin bugs fly?

Milkweed assassin bugs aren’t really capable of flight. They have underdeveloped wings that won’t support their body weight. They might be able to move and flutter them, but don’t expect to see milkweeds zooming around your azaleas.

15. Are milkweed assassin bugs beneficial?

Yes. They aren’t without flaws, of course, but many people think that the pros of milkweed assassin bugs outweigh the cons. In exchange for the occasional bite, you’ll get a natural form of pest control for your property.

16. How long do milkweed assassin bugs live?

Milkweed assassin bugs can live for several years.

They’re capable of surviving the winter, something that many bug species can’t do. Because of this, they have longer lifespans than some of the other creepy-crawlies in their habitats.

17. What eats a milkweed assassin bug?

There isn’t a definitive list of predators for the milkweed assassin bug. It’s possible that they’re killed by the same mammals and reptiles as other assassin bugs, but since there are more than 7,000 species under that umbrella, the list of possibilities is endless.

18. Is the milkweed assassin bug endangered?

No. While they’ve never been formally assessed by conservation groups like the IUCN, milkweed assassin bugs are so commonplace that they aren’t considered to be at risk for extinction. They exist in large numbers across multiple continents.

19. Why are milkweed assassin bugs called true bugs?

Most insects that get the “bug” label aren’t really bugs at all. This is because “bug” is an actual species classification that doesn’t extend to things like flies, bees and beetles. They have their own species.

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“True bugs” is a label that applies to the hemiptera order of insects. It includes milkweed assassin bugs as well as shield bugs, seed bugs, water bugs, flower bugs, and sweet potato bugs.

20. What do milkweed assassin bugs eat?

Milkweed assassin bugs prey on other insects. They’ll consume almost any bugs in a home or garden, including flies, beetles, worms, mosquitoes, and caterpillars.

This is one of the reasons why a farmer might deliberately introduce them to his crops: They won’t eat the vegetables, but they’ll eat the other insects that munch on the vegetables.

21. How do milkweed assassin bugs kill their prey?

Are you sitting down? Milkweed assassin bugs have a horrifying way of killing their victims.

For starters, they’re ambush animals, so they’ll hide among the leaves until an unsuspecting insect wanders by. Then, when the other creature least expects it, they’ll grab them with their sticky, resin-covered legs that are perfect for ensnarement.

This is when things get truly gross. With their long, tube-like suckers, the milkweed assassin bugs will pierce the flesh of their victims and inject an enzyme that liquefies their organs and tissue. When the other bugs are basically piles of goo covered in exoskeletons, the milkweed assassin bugs will suck them up through their tube.

Voila. Dinnertime.

22. Can milkweed assassin bugs take down larger bugs?

Yes. Milkweed assassin bugs are able to catch and kill bugs that are up to six times their own size! However, it should be noted that they usually prefer smaller prey.

This might be because larger prey takes longer to consume and leaves them open to danger. If their sucker is buried in their victim, it can’t be used to defend them from another animal.

33. What is the milkweed assassin bugs Latin name?

The scientific name of the milkweed assassin bug is Zelus longipes.

This comes from the Latin words for “Zelus” and “longfoot.”

34. Who was Zelus, and what’s his significance to the milkweed assassin bug?

Zelus was a deity in Greek mythology. He was one of the winged protectors that guarded Zeus’s throne, and he was known for his strong emotions of passion, envy, rivalry, and devotion.

The word “zeal” is derived from his name. There’s an entire genus of bugs named after him, and it includes the milkweed assassin bug, the pale green assassin bug, and the leafhopper assassin bug.

35. What other names does the milkweed assassin bug have?

The milkweed assassin bug is often confused with other types of assassin bugs, including “kissing bugs” that get their nickname for biting their victims near the lips.

However, true milkweeds are only classified as Zelus longipes, and they don’t have any other names aside from that one.

36. What’s the relationship between milkweed assassin bugs and fall armyworms?

Milkweed assassin bugs are very helpful in ridding an area of fall armyworms. Fall armyworms are an invasive species that can cause actual economic damage when they destroy large areas of crops. Milkweed assassin bugs can consume them in the caterpillar stage before they grow up and become pests.

For this reason, milkweeds are often the go-to choice for natural pest control in areas plagued by fall armyworms.

37. Are milkweed assassin bugs loud?

No. In fact, milkweed assassin bugs are so quiet that you might assume they’re totally silent. You’d need an amazing amplifier to hear the tiny noises that they produce when they rub their suckers against their chests.

38. Do milkweed assassin bugs carry disease?

Certain types of kissing bugs can carry parasites, but since these are transmitted through their blood-sucking, they aren’t a danger in milkweed assassin bugs. Milkweeds don’t cause any known diseases or disorders.

39. Where does the milkweed assassin bug live?

The native range of the milkweed assassin bug stretches from the southern U.S. to the middle of South America.

However, they can be found in many other locations as well. Since they’re so helpful to farmers, it isn’t uncommon for them to be deliberately bred in agricultural environments across North and South America.

40. What is the habitat of the milkweed assassin bug?

As ambush predators, milkweed assassin bugs like places where they can hide. They’re attracted to anywhere with foliage, including gardens, bushes, woods and shrubs. They’ve also been known to hide under porch patios or in the cracks of houses and sheds.

41. What do milkweed assassin bug eggs look like?

The eggs of milkweed assassin bugs are usually long and cylindrical. They measure between 2.0 – 2.3 millimeters, which makes them quite large for their insect family, and they’re brown without any additional markings.

They look simple from the outside, but when you put them under a microscope, you’ll see that they have a complex internal structure that includes everything from fertilizing membranes to temperature-controlling shells.

42. How many eggs do milkweed assassin bugs lay?

Female milkweeds usually lay around 15 eggs at a time in a densely-packed cluster. It’s unknown how many clusters that they create during a full reproductive cycle.

43. Do male and female milkweeds both participate in child-rearing?

Milkweed assassin bugs grow up so quickly that there isn’t a lot of child-rearing for mom and dad to do. However, both parents play a role in protecting the eggs when they’re at their most vulnerable:

  • The females hardly ever leave their egg clusters. When it’s feeding time, the males will bring back insects for them.
  • The males will stand guard over the egg clusters and protect them from potential threats. In one test, they stood their ground even as testers waved their hands around or mimed picking them up; milkweeds usually run from this kind of danger, but the dads refused to leave their eggs. In another test, when they were shown a realistic model of a wasp species that preys on eggs, they attacked it.

44. What are young milkweed assassin bugs like?

Young ones are called “nymphs.” They mature quickly and molt about five times before they’re considered adults.

One interesting fact about juvenile milkweed assassins is that they aren’t born with the glands that produce resin. It takes time to develop them. Until then, they swipe some of their mom’s goo from their leftover egg sacs. How’s that for family closeness?

45. Do milkweed assassin bugs hibernate in the winter?

No. They overwinter, but they don’t hibernate. Milkweed assassin bugs can still be spotted crawling around leaves in temperatures as low as 30°F – 40°F.

46. Where can I see the milkweed assassin bug?

If you live in the southern U.S., seeing a milkweed assassin bug might be as simple as sticking your head out of the window.

If you’re a bit further north, you might need to venture to a local animal exhibit. The good news is that milkweed assassin bugs aren’t rare, so you can find them in all kinds of zoos, botanical gardens and science centers.

Drink ‘Til You Drop

Most people hate them when they bite. Other people praise them when they kill off pests that would destroy farms and gardens. No matter which side of the fence that you land on, we hope that you learned something interesting from these milkweed assassin bug facts. They’re fascinating creatures despite the nasty nature of their diets!

Have any questions? Let me know in the comments!


Scroll Over Images and Click to Enlarge

FIGURE 1. Unlike assassin bugs in general, bee assassin bugs are good fliers.

FIGURE 2. Bee Assassin Bugs have sticky hairs on their front legs which help them secure their prey. Note that the tip of right front leg is missing.

FIGURE 3. Bee Assassin Bugs are usually dark in color with yellow or red markings on the sides of the abdomen. As is common in nature, the bright colors advertise their own distastefulness to predators including birds.

FIGURE 4. As its name would likely suggest, the bee assassin bug is commonly reputed to feed on bees. Some notations indicate that the Bee Assassin Bug is a major threat to honey bee populations but we have not yet seen unbiased, research-based findings to support or disclaim this contention.

Quick Facts

Common Name:

Bee Assassin Bug and Bee Killer Assassin Bug

Genus / Species:

Apiomerus crassipes

Size: ½ inch (adult stage)

Type of Beneficial:

Insect predator

Type of Metamorphosis:

Immature stages appear different from adults (i.e., complete metamorphosis)

Beneficial Stage(s):

Immatures (known as nymphs) and adults


Generalist feeders

Mounted Specimen?

Yes (mounted specimen for viewing available in insect collection at County Extension Office)

The Bee Assassin Bug (Apiomerus crassipes)

As its name would likely suggest, the Bee Assassin Bug is commonly reputed to feed on bees. Some notations state that Bee Assassin Bug is a major threat to honey bee populations but we have not yet seen unbiased, research-based findings to support or disclaim this contention. While we have observed Bee Assassin Bugs patrolling flowers in our Master Gardener Demonstration Gardens, they are mostly seen on leaves and stems—areas not likely to be visited by honey bees. In addition, most insect predators are generalist feeders and honey bees will be taken as prey by Bee Assassin Bugs which are ambush hunters.

Unlike many assassin bugs in general, Bee Assassin Bugs are good fliers. They have sticky hairs on their front legs which help them secure their prey. Bee Assassin Bugs are usually dark in color with yellow or red markings on the sides of the abdomen. As is common in nature, the bright colors advertise their own distastefulness to predators including birds. Adults are typically ½ inch in length.

General Overview of Assassin Bugs

Assassin bugs are widely distributed throughout the Galveston-Houston region. Assassin bugs are usually dark-colored, with combinations of gray, green and black and are members of a large family of bugs (known as Reduviidae). Assassin bugs are excellent predators and are general feeders; i.e., they prey on a diverse variety of insect pests in the garden and landscape including flies, mosquitoes, beetles and large caterpillars.

The aptly named assassin bugs often wait in hiding and ambush their prey. Typically, the eyes are large and set at the middle or rear of the head with a neck-like area behind the head. The antennae have four segments. Assassin bugs, like all true bugs, have piercing, sucking mouthparts (collectively called a beak) that are used to remove body fluids from the prey. The beak has three segments and rests within a groove between the front legs when it is not in use.

Once prey is captured and punctured, salivary secretions are pumped through a canal inside the piercing/sucking mouthpart. The salivary secretions not only serve to quickly immobilize prey but they also dissolve the prey’s internal tissues. This process enables the assassin bug to withdraw the bodily contents of its prey.

Like all members of the order Hemiptera, assassin bugs and ambush bugs go through a simple metamorphosis with egg, nymph and adult stages. In warm months, females lay eggs which are stuck in clusters to leaves and stems. After hatching, the wingless nymphs grow and molt 4 times (some species molt have up to 7 times) before becoming full-sized, winged adults. Adults are usually the overwintering stage.

In general, assassin bugs hunt on various types of vegetation, including trees, weeds and bushes. Assassin bugs are able to fly but they are poor fliers in general with some notable exceptions.

Although most assassin bugs are slow-moving and nonaggressive, they will use their rostrum in self-defense if handled carelessly. Such bites may be rather painful to humans because the bugs inject the same salivary secretion used to dissolve the tissues of their prey. This results in the death of a small area of cells at the site of the bite. The symptoms are an intense burning sensation, often followed by a small, itchy lump that may persist for several days. However, no true toxin is involved so it is rare for the reaction to last long or to extend beyond the site of the bite. Some bites occur when the bugs are purposely handled out of curiosity, but most happen through accidental contact while gardening or working in the open. The sharp pain associated with assassin bug bites is usually enhanced by the surprise accompanying the experience.

The beneficial qualities of assassin bugs far outweigh their negative potential, and learning to get along with these indispensable predators is in our own best interest.

Beneficials in the Garden & Landscape is an Earth-KindTM program coordinated through Extension Horticulture at Texas A&M University. Earth-Kind uses research-proven techniques to provide maximum gardening and landscape enjoyment while preserving and protecting our environment.

A clearer picture of how assassin bugs evolved

This photo shows a selection of different assassin bugs representing different evolutionary lineages. Credit: W. S. Hwang, Weinrauch Lab, UC Riverside.

Assassin bugs, so named because these insects lie in ambush for prey that they attack with speed and precision, are found all over the world. Nearly 140 species of these bugs are blood-sucking; because they can bite humans around the mouth, they are also called kissing bugs. All kissing bugs can spread Chagas disease, a neglected tropical disease that imposes an economic burden on society.

Surprising, then, that scientists’ understanding of the evolutionary history of assassin bugs is riddled with difficulty. The data are incomplete. Fossils, which exist for only a few groups of assassin bugs, are young, providing only patchy information on how these bugs evolved.

Now entomologists at the University of California, Riverside have produced a clearer snapshot of the entire evolutionary history of assassin bugs by integrating molecular, paleontological, behavioral and ecological data into their analyses. The result of their painstaking work is a new phylogeny—the representation of the evolutionary relationships between species—for assassin bugs. It includes the most number of assassin bugs to date and represents the most number of subfamilies.

“We can now zoom in on specific groups within the phylogeny to examine specific aspects of the evolution of that group,” said Christiane Weirauch, an associate professor of entomology who reconstructed the assassin bug phylogeny with her Ph.D. graduate student Wei Song Hwang. “Our phylogeny significantly improves our knowledge about relationships within assassin bugs and will guide future research work in understanding how some of the interesting prey specialization behaviors and prey capture techniques have evolved.”

Study results appeared last month in PLoS ONE.

“One significant improvement is the addition of several assassin bug species from the subfamily Reduviinae, the second largest subfamily of assassin bugs,” said Hwang, the first author of the research paper. “Previous phylogenies have a very limited representation of Reduviinae, which means the overall interpretation of the phylogeny is of limited value.”

This photo shows a representation of the diversity of blood-feeding kissing bug species in the world. Credit: W. S. Hwang, Weirauch Lab, UC Riverside.

Assassin bugs are estimated to have originated during the Middle Jurassic (~178 million years ago), making them a relatively old group of insects. They diversified significantly in the Late Cretaceous (~97 million years ago); indeed, nearly 90 percent of the existing species diversity we see today in assassin bugs started to diversify from this time onwards. The cause of this diversification remains unknown.

Blood-feeding kissing bugs

Weirauch and Hwang also determined that kissing bugs originated just 27-32 million years ago, the previous estimate being 107 million years ago. Mostly found in Central and South America, these bugs have evolved to feed on vertebrate blood—lizards, birds, opossums, armadillos, bats, etc., and humans—and can be found in diverse environments, from the Sonoran desert to the Amazon rainforest.

“The previous estimate of 107 million years ago linked the diversification of kissing bugs with the splitting of South America from Antarctica and provided a longer time-span for kissing bugs to speciate and spread across the continent and adapt,” Hwang said. “Our research shows that this is not the case. By including more data and improving estimation methods, our younger estimate of 27-32 million years ago matches the time when the hosts, mainly mammals and birds, were diversifying at a rapid rate in South America.”

The researchers caution that as natural environments get altered, more kissing bugs may be seen adapting to new environments and hosts rather than going extinct.

“The colonization of human settlements by wild kissing bugs we are witnessing now is thus likely to increase in intensity as more natural environments are replaced by human activities,” Hwang said.

With their comprehensive sampling of assassin bugs and large molecular dataset, Weirauch and Hwang also show that the blood-feeding kissing bugs either have a single origin or two separate but close origins. Until now, the possibility of two separate but close origins of kissing bugs had not been hypothesized nor demonstrated.

“The possibility that there are two separate lineages implies that there will be shared traits among the lineages, but also slight differences we need to be aware of when developing different preventative strategies,” Hwang explained. “A single origin, on the other hand, means we can expect common traits shared among all kissing bugs that can be targeted for control or monitoring.”

Building the Tree of Life

The current research is part of the scientific endeavor to reconstruct the entire Tree of Life—the biological concept that all living organisms are related and can be traced back to a single ancestor representing the origin of life on Earth.

“Reconstructing a phylogeny, a framework from which we can infer the evolutionary history of any group of organisms, is thus the first step towards understanding how life evolved, how different species relate to one another, how specific traits evolved over time, and why biodiversity occurs the way it does today,” Weirauch said.

Explore further

Assassin bugs trap spiders by mimicking prey (w/ Video) More information: PLoS ONE 7(9): e45523. doi:10.1371/journal.pone.0045523 Journal information: PLoS ONE Provided by University of California – Riverside Citation: A clearer picture of how assassin bugs evolved (2012, October 25) retrieved 1 February 2020 from This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

common name: milkweed assassin bug (suggested common name)
scientific name: Zelus longipes Linnaeus (Insecta: Hemiptera: Reduviidae)

Zelus longipes Linnaeus is commonly called the milkweed assassin bug, as it closely resembles the milkweed bug, Oncopeltus fasciatus (Dallas). It is also known as the longlegged assassin bug and the Zelus assassin bug (Bug Guide). Members of the genus Zelus belong to the subfamily Harpactorinae and are diurnal in nature. They are generalist predators feeding on a wide range of soft-bodied prey in garden and fields such as mosquitoes, flies, earthworms, cucumber beetles, and caterpillars (fall armyworm, rootworm, etc.).

Figure 1. Adult milkweed assassin bug, Zelus longipes Linnaeus, showing its long legs and beak (stylet), sitting on a sweet corn tassel. Photograph by Megha Kalsi, University of Florida.

Distribution (Back to Top)

Zelus longipes is widely distributed in southern North America (Gulf Coast and South Atlantic states; southern California and southwestern Arizona in United States), Central America, South America (except Chile) through central Argentina, and the West Indies (Hart 1986, Melo 2005, Wolf and Reid 2001, Cogni et al. 2000).

Description and Life Cycle (Back to Top)

This species exhibits great variation in size and color, which resulted in confusion in correct species identification in the past. The greatest color variation is observed in West Indies populations where individuals may be orange-brown, brownish-black and even entirely black (Hart 1986). The United States populations are distinctively orange and black in color. Adults and nymphs have a pear-shaped head, constricted neck and long hairy legs. Their piercing and sucking mouthparts have a three-segmented beak which, when at rest, is bent and held under the thorax in a groove.

Adults: Males are smaller than females. In California and Arizona populations, males averaged 16.1 mm and females 18.4 mm in length, while in Gulf Coast populations, males and females averaged 16.8 mm and 18.2 mm, respectively. In females, the terminal abdominal segment is platelike or flattened, while in males it is cuplike or rounded (Hart 1986). Adults are known to overwinter.

Adult Zelus longipes can be differentiated from other Zelus species based on the following morphological characteristics:

In the pronotum, humeral angles are unarmed and rounded,

Dorsal surface of insect ranges from brownish-red to brownish-black in color,

Parameres (or lateral lobes of male genital organ) are cylindrical and long, surpassing 1/4 the length of median lobes.

Figure 2. Adult female milkweed assassin bug, Zelus longipes Linnaeus, sitting on a sweet corn tassel. Photograph by Megha Kalsi, University of Florida.

Figure 3. Adults milkweed assassin bugs, Zelus longipes Linnaeus, mating in sweet corn field. Photograph by Megha Kalsi, University of Florida.

Eggs: The eggs are cylindrical and elongate in shape, non-ornamented, brown in color, with a light brown, cap-like structure (called the operculum) which has a central pore with a funnel-shaped opening. The egg can be divided into two parts: the operculum (which is attached to the anterior pole of the egg) and main eggshell or chorion (Wolf and Reid 2000). Each egg measures 2.0-2.3 mm in overall length while the appendage is 0.5 mm long (known to be longest among all bugs). The rest of the main eggshell measures 1.5 mm in length. The main eggshell is widest at the posterior pole (0.53 mm) and narrows near the anterior pole (0.32 mm). The anterior pole is flat and is attached to the anterior appendage at a distinct waist-shaped junction. Viewed sideways, the eggshell appears to be laterally flattened with a slight curvature inwards (Wolf and Reid 2000).

Figure 4. Eggs of the milkweed assassin bug, Zelus longipes Linnaeus, showing the central pore (a) in the operculum of one egg, and the mucilaginous layer (b) surrounding the main eggshells but not the opercula. Photograph by Megha Kalsi, University of Florida.

Figure 5. Lateral view of eggs of the milkweed assassin bug, Zelus longipes Linnaeus, showing the operculum (a), the main eggshell (b), the waist-like junction (c), and the egg flattened at one side with a slight curve inwards (d). Photograph by Megha Kalsi, University of Florida.

The main eggshell has a smooth surface. The anterior appendage exhibits a highly diversified architecture internally when viewed under SEM (Scanning electronic microscope). The cylindrical outer layer of the anterior appendage is called a veil, which is continuous with the main eggshell and roughly equal in diameter. The veil folds inwards at the anterior pole forming a double layer and within this are many honeycomb-like structures. The function of the veil is to regulate humidity for the developing embryo. Partially removing the veil exposes a topographical arrangement of the important components of the anterior appendage which are micropyles (present at the base of veil) and operculum. The micropyles help in gaseous exchange while the operculum is a plate-like structure attached to the anterior part of egg that is lifted during hatching. Eggs are laid in a cluster of 15 or more, cemented at the base and covered with viscous material (except for the anterior appendage as its function is to protect the aeropyles from clogging) (Wolf and Reid 2000).

Figure 6. An egg mass of the milkweed assassin bug, Zelus longipes Linnaeus, surrounded by a mucilaginous layer and laid on the lower surface of a sweet corn leaf. Notice that the egg opercula are not covered. Photograph by Megha Kalsi, University of Florida.

Figure 7. An adult female milkweed assassin bug, Zelus longipes Linnaeus, ovipositing eggs in a cage. Photograph by Megha Kalsi, University of Florida.

Nymphs: Zelus longipes passes through five nymphal instars before developing into adults.

First instar: The body is elongated with a differentiated neck and is light brown in color, measuring 2.61 mm in length. The head is pyriform in shape, measuring 0.80 mm in length and 0.50 mm wide with sparse setae. The prominent reddish-brown eyes are 0.22 mm wide (ocelli are absent). The antennae are filiform, setose and 3.98 mm long. The legs are dark brown in color, except for the coxa which is light brown. The abdomen is dark brown to orange in color, and appears round in form with a few setae on the last segments. This stage lacks wing pads (Melo et al. 2005).

Figure 8. First instar nymphs of the milkweed assassin bug, Zelus longipes Linnaeus, hatching out of the eggs and slowly extending their legs. Photograph by Megha Kalsi, University of Florida.

Figure 9. First instar nymph of the milkweed assassin bug, Zelus longipes Linnaeus, showing dorsal view (left and center) and ventral view (right). Photograph by Megha Kalsi, University of Florida.

Figure 10. A mass of first instar nymphs of the milkweed assassin bug, Zelus longipes Linnaeus, hatching out of eggs laid on a sweet corn leaf. Photograph by Megha Kalsi, University of Florida.

Figure 11. First instar nymph of the milkweed assassin bug, Zelus longipes Linnaeus, feeding on a nymph of the minute pirate bug, Orius insidiosus (Say). Photograph by Megha Kalsi, University of Florida.

Second instar: The body now is more elongated measuring 4.26 mm in length with pale brown color and orange tinge (Melo et al. 2005). The head is also more elongated, 1.08 mm long and 0.67 mm wide, compared to the previous instar. The legs are black with lightly colored coxa. And the abdomen is rounded and setose with faintly visible sweat glands. Wing pads are now present, and are dark brown to black in color and 0.35 mm long.

Figure 12. Anterior view of a second instar nymph (a) and the exuvia (b) of the milkweed assassin bug, Zelus longipes Linnaeus. Photograph by Megha Kalsi, University of Florida.

Third instar: The body is elongated and 5.73 mm long ( Melo et al. 2005). The head is 1.56 mm long and 0.78 mm wide. It is uniformly orange with setae. The antennae are 7.5 mm long, with color and banding similar to the previous instar. Legs and wing pad color are same as the previous instar. The length of the wing pad now averages 0.84 mm. The abdomen is rounded, with setae and visible scent gland openings.

Figure 13. Dorsal view of a third instar nymph and exuvia (insert) of the milkweed assassin bug, Zelus longipes Linnaeus. Photograph by Megha Kalsi, University of Florida.

Figure 14. Lateral view of a third instar nymph of the milkweed assassin bug, Zelus longipes Linnaeus. Head is to the right and the stylet (pointing to the rear in the resting position) is visible under the head. Photograph by Megha Kalsi, University of Florida.

Fourth instar: The total body length is 7.14 mm (Melo et al. 2005). The head width and length is 0.97 mm and 2.05 mm, respectively. Antennal length is now 10.23 mm,while the antennae are black and have two distal pale bands (light brown) on the first segment. The second and third antennal segments are setose. Legs are black with three pale bands, one on the forefemur and two on the median and hind femora. The wing pads are black, setose and 1.37 mm in length. The abdomen is more elongated and setose as compare to previous instars, and measures 2.67 mm in length and 0.65 mm in width. The posterior portion is yellow in color with prominent black dorsal spots present on the VI and VII sternites.

Fifth instar: The orange body is elongated, measuring 11.29 mm (Melo et al. 2005). Head length and width is 2.77 mm and 1.26 mm, respectively. Eyes are conspicuously black. Antennae, measuring 14.56 mm in length, are similar to previous instars in regard to color, band patterns and setae. The second segment of the antenna has five trichobothria (elongated, non-tapered setae) while the remaining three segments have abundant setae. The wing pads are 3.54 mm in length, setaceous and black. The abdomen is orange, setaceous and is 4.97 mm long and 1.77 mm wide. Lateral edges of the abdomen show thin whitish-yellow stripes.

Economic Importance (Back to Top)

While a generalist predator, Zelus longipes is also important as a predator of important economic pests such as the fall armyworm, Spodoptera frugiperda (Cogni et al. 2000), the Asian citrus psyllid, Diaphorina citri (Hall 2008), and the genista broom moth, Uresiphita reversalis Guenée (Carrel 2001).

While not a threat to humans, if not handled properly, a Zelus longipes bite can cause a burning sensation with swelling that may last for several days.

Feeding Behavior (Back to Top)

The strategy Zelus longipes uses to catch its prey is known as the “sticky trap strategy.” Like many ambush bugs, Zelus longipes attacks prey after hiding inside foliage with its forelegs raised in the air. The forelegs of Zelus longipes are covered with a viscous material which acts as a glue, trapping the prey. Zelus longipes then rapidly paralyzes its prey by inserting its stylets into the host body and and prepares to feed through extra-oral digestion. Extra-oral digestion is a mode of digestion where a predator releases enzymes into its prey to dissolve the host’s tissue, and later sucks up the dissolved liquid using its stylet as a straw (Wolf and Reid 2001). Zelus longipes can feed on prey that may be up to six times their own size. But with increasing prey size the handling and feeding time for Zelus longipes also increases, allowing them to become vulnerable to other predators (Cogni et al. 2000).

Figure 15. Adult milkweed assassin bugs, Zelus longipes Linnaeus, showing hiding or ambush behavior. Photograph by Megha Kalsi, University of Florida.

Figure 16. Adult milkweed assassin bug, Zelus longipes Linnaeus, lying in ambush (in the shadows upper left) with its forelegs raised just before attacking its prey, a cornsilk fly, Euxesta stigmatias Loew, (lower right). Photograph by Megha Kalsi, University of Florida.

Figure 17. Adult female milkweed assassin bug, Zelus longipes Linnaeus, paralyzing its prey, a cornsilk fly, Euxesta stigmatias Loew, by inserting stylets. Photograph by Megha Kalsi, University of Florida.

Figure 18. Adult female milkweed assassin bug, Zelus longipes Linnaeus, feeding on a cornsilk fly, Euxesta stigmatias Loew. Photograph by Megha Kalsi, University of Florida.

Figure 19. Nymph of the milkweed assassin bug, Zelus longipes Linnaeus, feeding on Euxesta annonae Fabricius, a picture-winged fly. Photograph by Megha Kalsi, University of Florida.

Selected References (Back to Top)

  • BugGuide. (October 2009). Species Zelus longipes – Milkweed Assassin Bug. (21 August 2018).
  • Carrel JE. 2001. Response of predaceous arthropods to chemically defended larvae of the pyralid moth Uresiphita reversalis (Guenée) (Lepidoptera: Pyralidae). Journal of the Kansas Entomological Society 74: 128-135.
  • Cogni R, Freitas AVL, Filho FA. 2000. Influence of prey size on predation success by Zelus longipes L. (Het., Reduviidae). Journal of Applied Entomology 126: 74-78.
  • Hall DG. (2008). Biological control of Diaphorina citri. Concitver. (21 August 2018).
  • Hart ER. 1986. Genus Zelus Fabricius in the United States, Canada, and Northern Mexico (Hemiptera: Reduviidae). Annals of the Entomological Society of America 79: 535-548.
  • Melo MC, Coscaron MC, Filho BA. 2005. Immature stages of Zelus longipes (Heteroptera: Reduviidae, Harpactorinae). Transactions of the American Entomological Society 31: 101-110.
  • Ralston JS. 1977. Egg guarding by male assassin bug of the genus Zelus (Hemiptera: Reduviidae). Psyche 84: 103-107.
  • Wolf KW, Reid W. 2000. The architecture of the anterior appendage in the egg of the assassin bug, Zelus longipes (Hemiptera: Reduviidae). Arthropod Structure and Development 29: 333-341.
  • Wolf KW, Reid W. 2001. Surface morphology of legs in the assassin bug Zelus longipes (Hemiptera: Reduviidae): A scanning electron microscopy study with an emphasis on hairs and pores. Annals of the Entomological Society of America 94: 457-461.


Scroll Over Images and Click to Enlarge

FIGURE 1. The Milkweed Assassin Bug provides excellent insect control and has distinctive red and black coloration. During on mild days, Milkweed Assassin Bugs continue to be active through the winter season in Galveston-Houston region.

FIGURE 2. Milkweed Assassin Bugs have very long antennae and legs. Note the defensive posture towards the camera and photographer!

FIGURE 3. Immature stages of the Milkweed Assassin Bug do not have fully-developed wings (immature wings are know as wing pads). Immature stages are known as nymphs and are voracious predators.

FIGURE 4. Two similar-sized adult milkweed assassin bugs “share” a fly for mealtime.

Quick Facts

Common Name:

Milkweed Assassin Bug

Genus / Species:

Zelus longipes

Size: 1/2 inch

Type of Beneficial:

Insect predator

Type of Metamorphosis:

Immature stages are similar in appearance to adult stage (i.e., simple metamorphosis)

Beneficial Stage(s):

Immatures (known as nymphs) and adults


Wide variety of prey including flies, caterpillars, beetles, mosquitoes, etc.


Widespread across the county

Mounted Specimen?

Yes (mounted specimen for viewing available in insect collection at County Extension Office)

The Milkweed Assassin Bug (Zelus longipes)

Several species of assassin bugs have widely known common names (ex., the Masked Hunter Assassin Bug, the Spined Assassin Bug) but the only common name found for Zelus longipes is Milkweed Assassin Bug.

Nevertheless, the most commonly occurring species assassin bugs in Galveston County are Zebus longipes. The Milkweed Assassin Bug is attractively colored in bright red and jet black. We regularly see them patrolling the plants throughout the year in our Master Gardener Demonstration Garden adjacent to the County Extension Office. They are surprisingly active on winter days when temperatures are mild even when preceded by short periods of very cool (mid- to low-thirties) days!

Determining the scientific name of this insect predator required some effort. We solicited the assistance of Dr. William M. Johnson (our County Extension Agent-Horticulture & County MG Program Coordinator) who in turn enlisted the assistance of three Extension Entomologists for identification of this insect.

Milkweed Assassin Bugs are widespread in the Galveston County area and they are highly beneficial insects. They eat a variety of insects including aphids, armyworms, stink bugs, houseflies, etc. Milkweed Assassin Bugs have a bright red-colored body with long black legs, black wings and long black antenna.

Local gardeners are becoming better aware of this beneficial insect based upon the increasing numbers of specimens submitted to the County Extension Office for identification over the last few years. The Milkweed Assassin Bug is a very effective and abundant insect predator—they are worth conserving in our gardens and landscape!

General Overview of Assassin Bugs

Assassin bugs are widely distributed throughout the Galveston-Houston region. Assassin bugs are usually dark-colored, with combinations of gray, green and black and are members of a large family of bugs (known as Reduviidae). Assassin bugs are excellent predators and are general feeders; i.e., they prey on a diverse variety of insect pests in the garden and landscape including flies, mosquitoes, beetles and large caterpillars.

The aptly named assassin bugs often wait in hiding and ambush their prey. Typically, the eyes are large and set at the middle or rear of the head with a neck-like area behind the head. The antennae have four segments. Assassin bugs, like all true bugs, have piercing, sucking mouthparts (collectively called a beak) that are used to remove body fluids from the prey. The beak has three segments and rests within a groove between the front legs when it is not in use.

Once prey is captured and punctured, salivary secretions are pumped through a canal inside the piercing/sucking mouthpart. The salivary secretions not only serve to quickly immobilize prey but they also dissolve the prey’s internal tissues. This process enables the assassin bug to withdraw the bodily contents of its prey.

Like all members of the order Hemiptera, assassin bugs and ambush bugs go through a simple metamorphosis with egg, nymph and adult stages. In warm months, females lay eggs which are stuck in clusters to leaves and stems. After hatching, the wingless nymphs grow and molt 4 times (some species molt up to 7 times) before becoming full-sized, winged adults. Adults are usually the overwintering stage.

In general, assassin bugs hunt on various types of vegetation, including trees, weeds and bushes. Assassin bugs are able to fly but they are poor fliers in general with some notable exceptions.

Although most assassin bugs are slow-moving and non-aggressive, they will use their rostrum in self-defense if handled carelessly. Such bites may be rather painful to humans because the bugs inject the same salivary secretion used to dissolve the tissues of their prey. This results in the death of a small area of cells at the site of the bite. The symptoms are an intense burning sensation, often followed by a small, itchy lump that may persist for several days. However, no true toxin is involved so it is rare for the reaction to last long or to extend beyond the site of the bite. Some bites occur when the bugs are purposely handled out of curiosity, but most happen through accidental contact while gardening or working in the open. The sharp pain associated with assassin bug bites is usually enhanced by the surprise accompanying the experience.

The beneficial qualities of assassin bugs far outweigh their negative potential, and learning to get along with these indispensable predators is in our own best interest.

Beneficials in the Garden & Landscape is an Earth-KindTM program coordinated through Extension Horticulture at Texas A&M University. Earth-Kind uses research-proven techniques to provide maximum gardening and landscape enjoyment while preserving and protecting our environment.

Deadly kissing bug spreads Chagas disease throughout Texas


Don’t be fooled by the kissing bug’s innocent name.

Its painless bite can be deadly, especially for human babies, people with immune deficiencies and puppies. And the insect lives throughout Texas.

This bug actually is many insects from a family of bugs that can all carry a parasite that infects mostly people, dogs and small mammals with Chagas disease, aka the silent disease. Texas has seven species of kissing bugs. On average, they vary in diameter from the size of a penny to a quarter, with dark backs that sometime are orange- or fringed in red. They look similar to a stinkbug, but with a distinctive pointed snout.


Chagas disease was once believed to be a Latin American problem, but the infection is spread mostly by an insect that lives in 27 states, but mostly in Texas, Arizona, and New Mexico.

Variations of this triatomine bug are called the conenose bug, bloodsucker, Walapai tiger, and Hualapai tiger. Hispanic communities in Texas may refer to it as chinché mala, according to an online publication by Texas A&M University.

Studies indicate between 50 percent and 64 percent of kissing bugs carry the deadly parasite that causes Chagas, which is considered a major neglected tropical disease, according to the U.S. National Library of Medicine. The World Health Organization estimates that 8 to 10 million people are infected worldwide, mostly in Latin America. The noncontagious disease is named after Carlos Chagas, who first described it in 1909. In 2013, Chagas was listed as a disease that must be reported to the Texas Department of State Health Services, but Chagas is not reportable in dogs.

In 2015, the Centers for Disease Control and Prevention awarded $544,329 grant to the University of Texas Health Science Center at Houston School of Public Health to conduct outreach and education on Chagas disease in South Texas.

“The kissing bug is everywhere,” said Paula Stigler-Granados, an assistant professor in the Department of Management, Policy & Community Health at the School of Public Health in San Antonio. “It’s in Houston, it’s in San Antonio, it’s in Corpus Christi. And many people infected with the disease have been bitten many times.”

Stigler-Granados leads the 100-member Chagas Task Force, involving doctors, university researchers, veterinarians, and entomologists. Their goal is specifically focused on the disease in Texas, with an emphasis on raising awareness among healthcare providers about this important but neglected health threat that is under-reported and often misunderstood.

The Chagas Task Force just published a guide to help Texans learn more and guard against the health risks for themselves and their pets.


The bug is most prevalent in Mexico, Central and South America. But it has been found in 27 southern United States, and mostly in Texas, Arizona, and New Mexico.

Once restricted to rural and blighted areas in the United States, the kissing bug’s range is expanding into urban and suburban neighborhoods, said Melissa Nolan, assistant professor of epidemiology at the Arnold School of Public Health at the University of South Carolina. One recently was discovered in an urban Houston home, said Nolan, who researched Chagas in humans for years at Baylor College of Medicine. Stigler-Granados has seen the insidious vector near her San Antonio home.

Researchers at Texas A&M University College of Veterinary Medicine have collected more than 5,000 kissing bugs since 2012. Nearly all came from Texas. Many came from outdoor patios and dog kennels, a percentage were collected from inside homes, according to researchers at the Hamer Lab at Texas A&M University.

“We generally let folks know that approximately 55-65 percent of the kissing bugs that we test are positive for (the Chagas parasite),” said the Hamer Lab’s Rachel Curtis-Robles, with the Department of Veterinary Integrative Biosciences College of Veterinary Medicine at Texas A&M.

Kissing bugs are nocturnal, blood-feeding insects that can fly. They mostly are seen during warmer months around dog kennels, woodpiles, cracks and crevasses, rock piles, beneath wooden decks, hunting cabins, deer blinds, under tree bark and in outdoor sheds or patios. They are sometimes attracted to outdoor lights.


Insecticides can kill kissing bugs, but because they can fly, localized spraying may not be very effective. Environmental management works best. Remove wood and brush piles in or near yards and play areas for children and pets. Clean tool sheds and make sure there are no rat nests on or near your property, or wood/brush piles near the home. Keep pet food indoors. Turn off outdoor lights. If you find one, the Texas health department will test bugs for the parasite.


The first confirmed case of chagas known to have been contracted within the United States occurred in Corpus Christi in 1955. Scientists concluded the 10-month-old girl was infected in a home where kissing bugs lived. The child ran a fever for days, and suffered a rash and swelling, but survived.

Researchers say about one in 6,500 Texan are infected with chagas and most show no symptoms. This infection rate is higher than thought before, Nolan said.

Most Texas Chagas cases occur around San Antonio, southward and along the Mexico border. But they also have been found along the U.S. Highway 35 corridor and in Houston. The Centers for Disease Control and Prevention estimates more than 300,000 people in the United States have the disease and 315 babies are born with Chagas in the United States annually.

In recent years, more than 70 confirmed human locally acquired infections in the United States have been published. These published studies are a good indicator that physician awareness is improving, Nolan said. More than 90 Chagas infections were reported to the Texas Department of State Health Services from 2013 to 2016. This only scratches the surface, Nolan said.


The CDC estimates 8-10 million people have Chagas in Mexico, Central America, and South America, where the disease is considered endemic. But it has been infecting people and dogs in the United States for decades, without being reported. Many of these victims show mild or no symptoms. Researchers suspect a growing number of infections in the United States are coming from home-grown kissing bugs.


In additional to geographic and socioeconomic risk factors, people who are most susceptible to Chagas live in poverty or rural settings, or who spend time in the outdoors camping, hiking or hunting. Patients with HIV or who are immune compromised also are at greater risk.


The insect’s contradictory label derives from its habit of accessing human blood near the mouth. This often occurs when the victim is asleep, aided by the insect first numbing the injection area.

After the bug gets its fill of blood, it defecates on or near the wound, sometimes infecting the victim with the chagas parasite through the wound, mouth, nose or eyes. The parasite resides in the insect’s digestive tract.


The parasite can be transmitted by blood transfusions; from an infected mother to her child during pregnancy; or from the consumption of uncooked food contaminated with feces from an infected insect. No cases have been confirmed from blood transfusions in the United States since 2007, when testing began, Stigler-Granados said.


Unlike a mosquito bite or bee sting, you may not know immediately or ever whether you’ve been bitten. Within a week, the bite area may become red or purple, swollen or look like a boil. Painless swelling of an eyelid is common. Some victims experience brief episodes of low-grade fever or a non-itchy skin rash, diarrhea, vomiting, stomach ache or loss of appetite, fatigue or body aches. Heart and digestive problems may develop years, or decades later.


Infections may result in mild or no symptoms. The most common signs of infection are fever and swelling around the site of the bite, where the parasite entered the skin, nose or mouth. Acute infection is rare, but may result in severe inflammation of the heart muscle or the brain. This is most common in young dogs.

Many infected people may not show symptoms for life. An estimated 30 percent of infected people will develop debilitating and sometimes life-threatening conditions. Complications of chronic Chagas disease may include: heart rhythm abnormalities that can cause sudden death; dilated heart that doesn’t pump blood well; a dilated esophagus or colon, leading to difficulties with eating or passing stool, according to the CDC. The most severe symptom of chronic Chagas is heart failure. About 30 percent of Chagas patients who are diagnosed with heart failure are likely to die within three years.


There is no vaccination that protects against Chagas for either dogs or humans. Treatment in infants younger than 1 is an effective cure, according to the Chagas Coalition. The U.S. Food and Drug Administration recently approved benznidazole for use in children 2-12 years old. It is available through your doctor. The drug, Nifurtomox, is available to physicians through the CDC. Studies have documented that treatment is only effective when given prior to the onset of heart disease.


If you’ve ever seen a kissing bug in or around your home, cabin, deer blind, or tent, or think you’ve been bitten by a kissing bug, talk to your doctor about options or consult the Chagas Task Force. There are commercially available lab tests for Chagas disease and most local and state health departments can help patients and health-care providers learn more about treatments. To find a clinic in your area, consult the American Society of Tropical Medicine. The test usually is covered by insurance. Consult the Chagas Task Force. If you find a kissing bug, carefully capture it and consult your state health department, or photograph it and post it on the Chagas Task Force Facebook page.


Chagas-related heart failure in the United State costs nearly $1 billion annually, according to Research America.


The kissing bug can infect all dogs of all breeds, though rarely. This happens in three ways, either from feces deposited after a bite; by ingesting the insect or its feces; and by congenital transmission from mom to puppies. Infections are found in both rural and urban areas. Young dogs seem to be most susceptible, but this may be the result of puppies eating the bug. In some cases, death occurs within three weeks. But, as in humans, most dogs with the disease may show no obvious symptoms for a time.

Common symptoms of acute Chagas include diarrhea, lethargy, seizures, swollen lymph nodes, fluid retention, and heart failure. Chronic symptoms include lethargy, fainting, increased heart rate or abnormal heart rhythm, and fluid buildup in the abdomen or lungs. Most often, the disease is silent for years while it damages the heart and other organs.

Insect control is the best defense. Consult a licensed pest control professional. The insects can live in cracks and crevices of wood and rocks. They are attracted to the heat and carbon dioxide emissions coming from mammals and are most active at night. Again, there is no vaccine or cure, though a new drug is undergoing FDA review.

The Texas A&M College of Veterinary Medicine is leading the charge against Chagas by combining studies of vector populations, wildlife reservoirs, domestic dogs, parasite genetic strains, laboratory animals, and human risk. The public may submit photos of suspected kissing bugs for identification to [email protected] or through the website.

Swelling of an eyelid is a common symptom of the kissing bug bite. But many victims show no signs whatsoever. Photo WHO/TDR These are three common varieties of kissing bugs found in Texas. Photo courtesy Texas A&M Kissing bugs are found mostly outdoors, wherever there is a source of blood. David Sikes Caller-Times The Chagas parasite can infect all dog breeds in rural or urban areas. David Sikes Caller-Times Kissing bugs often are found in and around dog kennels. Caller-Times file The Chagas Task Force, involving doctors, university researchers, veterinarians, and entomologists, will publish this field guide to aid public awareness of this under-reported and misunderstood disease. UT Health Science Center The best defense against the kissing bug is to eliminate this kind of habitat near the home. David Sikes Caller-Times Kissing bugs are nocturnal, blood-feeding insects that prefer warm conditions, cracks and crevasses. David Sikes Caller-Times Texas has seven varieties of the kissing bug. Photo Wikimedia Commons The kissing bug is found in 27 states in the United States, where it likely has always lived undetected. Photo courtesy Texas A&M

Interested in this topic? You may also want to view these photo galleries:

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Texas Chagas Task Force Field Guide on Facebook:

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Assassin Bug Control: How to Get Rid of Assassin Bugs

This page is a general Assassin Bugs control guide. Using the products and methods suggested you will get control of Assassin Bugs. Follow this guide and use the recommended products and we guarantee 100% control of Assassin Bugs.

Assassin Bugs are insects that have steadily become a growing issue within homes and businesses. Depending on the species, they can vary in appearance, but they all share the following traits: an elongated head, long thin legs, and an extended piercing mouthpart they use to attack their prey.

They are commonly found outdoors around gardens where they eat a variety of insects. However, Assassin Bugs can very easily enter a home in search of dark, secluded areas where it is cool. If your yard offers them an ample supply of insects, they might set up camp, and due to their attraction to lights, might slip into your home.

Assassin Bugs are capable of nasty bites which can create allergic reactions. Kissing Bugs, a species of Assassin Bug, is known to spread a parasite that causes Chagas disease, a potentially fatal illness for humans. For this reason, it’s important to carry out a control program if you’ve discovered Assassin Bugs in or around your home.


Assassin Bugs can be identified by their long and narrow heads and by their elongated mouthparts which they use to pierce and suck fluids out of their victims (usually insects). There are over 7,000 species and their identification can be tricky. It is better to identify them by the areas where they are most commonly found and by their size.

  • Indoors you’re more likely dealing with Kissing Bugs and Milkweed Assassin Bugs. Kissing Bugs are about 1 inch in length and are generally dark-colored with colorful orange markings around their body. Milkweed Assassin Bugs measure about 16 to 18 mm in length and are known to overwinter in homes.
  • Outdoors you’re probably contending with Wheel Bugs and Ambush Bugs. Ambush Bugs have shorter heads than most assassin bugs and front legs that look similar to praying mantis legs. Wheel Bugs are the biggest Assassin Bugs measuring about 1 1/2 inch in length. They have a cog-wheel shaped crest on their body, which is how to they got their name.

If you cannot determine your exact species of Assassin Bug you are dealing with, then continue on, this guide will treat both indoor and outdoor Assassin Bug issues.


Inspection of your property is essential for Assassin Bug control. Before you can treat you need to know where they are located and the places where they might be entering your structure. During the inspection, you will be looking for assassin bugs and potential entry points.

Where To Inspect

Indoors you’re looking for cracks and crevices where they may hide. Outdoors is where you’ll have better luck. Search in flower beds, mulch, leaf litter, yard debris, woodpiles, and under rocks.

What To Look For

You’re looking for Assassin Bugs and possible entry points. Indoors they might be less common to find, but outdoors near landscaping and flowerbeds is where you want to focus your inspection. If you have already seen your fair share of Assassin Bugs focus your search on possible entry points in your structure. Look around the foundation of your home for any cracks and crevices they might use to get inside. Note the locating where you have seen the Assassin Bugs. These will be the places where we will apply treatment.


Once you have confirmed Assassin Bug activity it is time to begin treatment. Remember to first read all product labels and follow the application instructions on these labels, and stay safe by wearing personal protective equipment.

Step 1 – Outdoor Treatment

Treatment for Assassin Bugs should start outdoors by killing off the insect population that is present in order to take away the Assassin Bugs food source. For this we recommend a broadcast treatment of Bifen LP Granules and a perimeter treatment of Reclaim IT. Bifen LP is a great granular insecticide that will provide protection for up to 90 days. Reclaim IT is a liquid insecticide that will be used to create a barrier around your property to kill, repel, and prevent insects from coming inside, including Assassin Bugs.

Bifen LP

Bifen LP Granules is a granular insecticide that is labeled to treat many different lawn insects, including beetles. Bifen LP has a residual effect that can last up to 3 months and can be broadcast over your entire yard to reduce the insect population.

The typical application rate is 2.3 pounds of Bifen LP to treat 1,000 square feet of lawn. To broadcast the Bifen LP Granules, you could use either a push spreader or a hand spreader like the Plantmates Scatterbox. While both styles are easy to use, a broadcast may be better suited for larger lawns as it holds more granules than a hand spreader and can cover a lot of ground in a short amount of time. If you need to spread granules on a flowerbed, around trees or are covering a smaller area and want to do it quickly yet precisely, the Plantmates Scatterbox hand spreader is ideal.

After measuring the square footage of your lawn (measure and calculate your lawn’s length x width), add the appropriate amount of Bifen LP to your spreader and then broadcast it uniformly over your entire lawn while walking at a steady pace. Apply all over your lawn, in flowerbeds, landscaping, mulched areas, and where Assassin Bugs have been seen. Remember to water the areas treated after application to activate the product.

Do not let people or pets enter the areas treated until 2 to 4 hours have passed.

Reclaim IT Insecticide

Reclaim IT is a broad-spectrum insecticide that is labeled for over 70 insect pests. It also has a long residual effect that continues to kill for up to 90 days after application.

To apply Reclaim IT, simply mix water in a hand pump or hose-end sprayer then add Reclaim IT at a rate of 1 oz per gallon to cover 1,000 sq. ft. Spray around the perimeter of your structure by spraying three feet up and three feet out from the foundation. Also spray window frames, door frames, cracks and crevices, electrical/plumbing penetrations in the foundation. Spray the whole perimeter of your structure.

Next, you will spray the yard as a broadcast treatment for application rates check the label. you will spray it all around your yard and will also apply it in ornamentals, and landscaping. Remember not to let people or pets enter the area until the spray has dried or 2 to 4 hours have passed.

Step 2 – Indoor Treatment with Fipro Aerosol

To protect your home indoors against Assassin Bugs we recommend Fipro Aerosol. Fipro is a foaming aerosol that contains the active ingredient Fipronil and comes ready to use. Thanks to it’s foaming capabilities, it is great to use in the small cracks and crevices where Assassin Bugs like to hide.

Simply shake, and insert with its injection straw, to small cracks and crevices found inside your home, the foam will spread inside these cracks and crevices and the product will be applied. Apply Fipro in small openings near baseboards, or openings around window frames, or any crack or crevice found inside your home.


Prevention is the key to obtain complete control. Some things you can do to keep you property Assassin bug-free include trimming back vegetation and preventing it from touching your structure. Cleaning your yard, making sure there are is no wood, leaf, or vegetation debris, will get rid of the possible areas where insects may harbor, which will also drive away assassin bugs.

The best thing to do to keep Assassin Bugs away is to turn the lights off at night, especially in patios or outside in the yard. If you must keep the lights on you will have more luck with yellow bug bulbs. Applying Reclaim IT every 3 months as a perimeter barrier and Bifen LP every 6 months around the yard will also ensure that bugs will be kept away from your property. And finally, seal any crack and crevice on the outside of your structure that might lead insects inside. Utilize Stuf-Fit Copper Mesh in areas around the home, especially around plumbing lines to take away points of entry. By closing these cracks and crevices you will block their access into your home.

Key Takeaways

  • Assassin Bugs often infest gardens and lawns around the home that have a large insect population, as small insects are its primary food source.
  • Reduce the insect population with a broadcast treatment of Bifen LP Granules then conduct a perimeter barrier treatment of Reclaim IT to keep insects and Assassin Bugs away.
  • Exclusion and sealing off any possible entry points is the best way to not only prevent but to also control Assassin bugs. Regularly check your home for any possible entry points and fix them and maintain a debris-free yard, this will ensure insects have no harborage areas.

Bed Bug Life Cycle

Bed bugs are nocturnal, reddish-brown insects that feed on the blood of humans and other warm-blooded animals. These wingless insects have dorsoventrally flattened bodies that allow them to hide in areas such as floor cracks, carpets, beds and upholstered furniture.

Bed Bug Life Cycle Chart (click to enlarge)


Bed Bugs and Eggs

A bed bug’s life begins with an egg, grain like and milky white in color. Female bed bugs lay between one and five eggs each day and may lie up to 500 eggs within one lifetime. Eggs are laid singly or in clusters and are placed within tight cracks or crevices. The egg is approximately 1 mm in length and is comparable in size to two grains of salt. Within two weeks, eggs hatch and immature bed bugs begin immediately to feed.


Bed Bug Nymphs

These young bed bugs, or nymphs, pass through five molts before reaching maturity. Although nymphs appear similar to adults, they are smaller in size and are not yet sexually mature. Young nymphs are also yellow-white in color, while older nymphs and adults are reddish-brown. In order to complete a molting stage, each nymph requires a blood meal. At room temperature, nymphs molt and become adults within five weeks.


Upon reaching maturity, bed bug adults often make weekly feedings.

Adult Bed Bug

How Long Do They Live?
The life span of a bed bug most commonly ranges from four to six months. However, some bed bugs may live up to a year under cool conditions and with no food.

Bed Bug Control

Cimex lectularius L.

How to identify Bed Bugs?

Learn what Bed Bugs look like, and how to detect if you have a Bed Bug Infestation.

How do you get Bed Bugs?

Find out how Bed Bugs infiltrate your home and where they are attracted to.

How serious are Bed Bugs?

Learn about Bed Bug bites. their feces and how they can impact your health.

What Orkin does

Learn how Orkin handles Bed Bugs, homeopathic cures and the cost of Bed Bug extermination services.

Continue Learning

  • Anatomy of a Bed Bug
  • Insects Resembling Bed Bugs
  • Metamorphosis: what is that?

    Most of insects undergo some kind of transformation process during their life cycle in order to reach adulthood -also known as imago phase- (e.g. butterflies). This process is named metamorphosis, although its essence is far from that of metamorphosis performed by amphibians. But, have you not ever wondered why they do this transformation? Which are the sense and the origin of the metamorphosis of insects?

    Learn more about the different types of metamorphosis, the origin and sense of these transformations through this article.

    Metamorphosis of the Old World swallowtail (Papilio machaon) (Picture by Jens Stolt).

    Metamorphosis is a biological process by which animals develop after birth involving huge transformations and/or anatomical restructurations (both physiological and anatomical) until reaching adulthood.

    There are different groups of animals that develop by this process, however most of them don’t share the origin nor the nature of these transformations. Thus, while amphibian metamorphosis takes place by reorganization of youth preexistent organs, in insects it takes place a breaking of tissues and also the appearance of totally new cell clusters.

    Ecdysis or molting

    First of all, we must talk about molt in order to comprehend the metamorphosis of insects. What means molting? And why is it an essential process for insects and arthropods as a whole?

    Every single animal regenerates its external tissues in some way, i.e., those tissues that are in contact with the environment and that protect the organism from external pressures. E.g. mammals regenerate their epidermal tissues periodically; a lot of reptiles shed off their skin frequently; but, what’s about arthropods?

    Arthropods, which include the hexapods (group in which we can find all insects), are externally covered by a more or less hard exoskeleton. In contrast with other external animal tissues, the exoskeleton doesn’t detach progressively, and its lack of elasticity restricts the organism growth. So, this element becomes a barrier that limits their size while growing, and is for this that they have to break it and leave it away in order to keep on growing. This kind of molting is known as ecdysis, which is typical of ecdysozoa (arthropods and nematoda).

    Take a look at this video of a cicada molting!:

    Do all hexapods metamorphose?

    The answer is NO. However, it’s necessary to go deeper into the explanation.

    All hexapods molt in order to grow, but not all them undergo radical changes to reach adulthood (when they become able to breed). Thus, we can split hexapods into two main groups:

    AMETABOLOUS HEXAPODS (No metamorphosis)

    This group includes those hexapods traditionally known as Apterygota or wingless hexapods (Non insect hexapods –proturans, diplurans and colembolas- and wingless insects as Zygentoma or also known as Thysanura –e.g. silverfishes or Lepisma-) and Pterygota or winged insects that have suffered a secondary loss of their wings.

    Specimen of Ctenolepisma lineata (Zygentoma) (Wikimedia Commons).

    Since they have no wings at any moment of their life cycle, the youth phases of this kind of hexapods almost have no differences from the adult ones. Thus, the youth development is simple and they don’t undergo huge changes to acquire the adult physique; that is, there is no metamorphosis at any point of their life cycle. This kind of development is also known as direct development.

    Direct development or ametabolous development (Picture from

    Ametabolous hexapods can molt tens of times throughout their development (e.g. 50 times in silverfishes, more or less), even when they become sexually mature.


    This group includes Pterygota insects or winged insects (except for the ones that have secondarily lost their wings).

    Specimen of Sympetrum flaveolum (Picture by André Karwath)

    In contrast of the ones which have been explained above, the youth phases of metamorphic insects are very different from the adult ones; so, after several successive molts they undergo their last change, through which it emerges a winged adult able to breed. After reaching this phase, these insects become unable to molt again.

    Types of metamorphosis in insects

    So, only Pterygota insects undergo a truly metamorphosis, thanks to which they become winged insects and also reach sexual maturity. But not all these insects perform the same kind of change.

    There exist two main types of metamorphosis: the hemimetabolous one (simple or incomplete) and the holometabolous one (complex or complete). Which are their differences?

    Hemimetabolous metamorphosis

    In the simple, incomplete or hemimetabolous metamorphosis, young insects go through several successive molts until reaching adulthood (or imaginal) stage without going through a stage of inactivity (pupa) and/or stop feeding.

    Just after hatching, we referred the newborn as a nymph, which resembles a little to the adult ones (but still not having wings nor sexual organs). Usually, nymphal phases and the adult ones don’t share feed sources nor habitat, so they occupy different ecological niches; in fact, most nymphs have aquatic habits and they go to live on land after reaching maturity (e.g. mayflies).

    Adult specimen of the species of mayfly Ephemera danica (Imagen de Marcel Karssies).

    In this kind of metamorphosis, nymphs go through some successive molts thanks to which wings are gradually formed and their organism becomes bigger. Finally, nymphs perform their last molt, after which the adult emerges: a winged organism that is able to breed.

    Take a look to this scheme that sums up this process:

    ______Hemimetabolous development of a _______grasshopper (imagen extraída de

    These insects are also called Exopterygota (from Latin exo- = “outside” + pteron = “wings”), because in these organisms the wings are progressively and visibly formed at the outside part of their body.

    Holometabolous metamorphosis

    In general terms, it’s considered the most radical metamorphosis in insects and also probably the most well known transformation by all of us. The most famous example is the one performed by lepidopterans (butterflies and moths); but there are also more insects that are holometabolous, such as coleopterans (beetles), hymenopterans (bees, wasps and ants) and dipterans (flies and mosquitoes).

    In the complex, complete or holometabolous metamorphosis, insects are born as larvae, that is, a premature stage that doesn’t resemble anatomically nor physiologically to the adult. In addition, they don’t share feed sources nor habitat, as it is the case of hemimetabolous organisms. As in hemimetabolous insects, these larvae go through successive molts until reaching the size enough to undergo the metamorphosis, when they perform their last molt.

    Beetle larva (“Curl grub” by Toby Hudson – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons).

    After their last larval stage, larvae enter in a stage of inactivity, moment they stop feeding and remain motionless. This stage is known as pupal stage (when they become a pupa or a chrysalis in butterflies). Usually, larvae begin to resemble to the adults at the end of this stage due to the anatomical modifications that take place and also to the appearance of new organs and tissues.

    Pupal stage of Cetonia aurata (Coleoptera) (“Cetoine global” by Didier Descouens – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons)

    Once the transformation process ends, the organisms leave that motionless state and acquire their adult form that has wings and is totally mature.

    In summary, the scheme of this process could be:

    Holometabolous development of a lepidopteran (Picture from

    In contrast with hemimetabolous insects, the appearance of wings in holometabolous organisms takes place inside their body and become visible only at the end of the pupal stage. For this reason, they are also known as Endopterygota (from Latin endo-= “inside” + pteron=”wings”).

    Origin and function of insect metamorphosis

    Origin: the fossil record

    Insects are, as we discussed in previous articles, one of the animals with greater evolutionary success. Between 40%-60% of all insect species are holometabolous (complete metamorphosis), because of what we deduce that holometabolous metamorphosis was positively selected during the evolution of this group. In fact, fossil records suggest that this kind of metamorphosis appeared only once, so all holometabolous insects derive from the same ancestor.

    According to these data, wingless insects or ancient Apterygota and early winged insects were ametabolous. Then, all winged insects started to develop some kind of hemimetabolous metamorphosis during the Carboniferous and the Permian (300 Ma). Finally, the first insects considered as holometabolous appeared during the Permian period (280 Ma).

    What could be the reason of this positively selection?

    In the latest paragraphs, we talked about the different feeding sources and habitats of both youth and adult. The fact that different life stages of the same animal exploit different resources could prevent the intraespecífic competition (i.e. competition for resources between organisms of the same species). This fact would mean a great advantage for these organisms, so that holometabolous development, which is characterized for being divided in very different stages, could have been more successful than the hemimetabolous or the ametabolous.

    Thus, we can say the main functional sense of metamorphosis could be to minimize the intraespecífic competition for resources. But there is still more: the more specialized are the different stages of an insect, the greater would be the chance to exploit more and better the resources. E.g. in parasitic forms, the differences between different stages tend to be huge, because the difficult situations they have to face require a specific specialization in each moment of the life cycle.

    Larva and adult of Danaus plexippus (monarch butterfly) (sources: larva picture by Victor Korniyenko, Creative Commons; adult picture of public domain).

    . . .

    So, likewise the appearance of wings promoted the expansion and diversification of insects worldwide, the metamorphosis could have acted as a diversifying engine by increasing the capacity to exploit more and better resources.

    • Notes from the subject “Advanced Zoology” taken during my Biology studies at Universitat Autònoma de Barcelona (UAB).
    • Bellés X. (2009). “Origen y Evolución de la Metamorfosis de los Insectos”. Instituto de Biología Evolutiva (CSIC-UPF), Barcelona.
    • Jordán Montés F. (2013). “El universo de los insectos”. Mundi-Prensa Libros, Madrid.
    • Los Insectos. Reproducción y Metamorfosis (

    Main picture by Steve Greer Photography.

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