Mealworms in my house


Darkling beetle

Darkling beetle, (family Tenebrionidae), any of approximately 20,000 species of insects in the order Coleoptera so named because of their nocturnal habits. These beetles tend to be short and dark; some, however, have bright markings. Although found on every continent, they are more common in warm, dry climates. Most members feed on dry, decomposing vegetation or animal tissue. Some bore in wood; others feed on larvae or live in ant nests.

darkling beetleDarkling beetle (family Tenebrionidae).Erik Bjurstrom/Bruce Coleman Ltd.

Adult darkling beetles vary greatly in size and shape: from 2 to 35 mm (1/12 to about 1 1/2 inches) and from flat to cylindrical. The larvae are about 25 mm (1 inch) long, cylindrical, and wormlike.

The larvae of a widely distributed darkling beetle known as the mealworm (Tenebrio) are used as food for such pets as birds and fish. Both the mealworm and the smaller flour beetle (Tribolium confusum) are pests in dried foods. Remains of Tribolium have been found in a grain jar in an Egyptian tomb dating back to about 2500 bce. The flour beetle is also used in laboratory studies of population ecology, heredity, and behaviour because large numbers can be raised under a variety of experimental conditions.

The forked fungus beetle (Bolitotherus cornutus) is easily recognized by a pair of blunt hornlike projections on the head. The dark adult is 10 to 12 mm (0.4–0.5 inch) long and has wing covers that resemble pieces of bark. The larvae live in woody bracket fungi.

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The pinacate bug (Eleodes) is large and smooth with no hindwings. In dry climates the wing covers (elytra) are fused together to reduce evaporation of water from the body. When disturbed, the bug elevates the hind part of its body and secretes a foul-smelling oily fluid for protection.

Darkling Beetle (Various spp.)

A general and well-populated group, Darkling Beetles come in a variety of shapes, sizes, and colors and eat a myriad of things.

Darkling Beetles can be found under stones, inside hollowed logs, and roaming sandy dunes and deserts. Many are completely black, but some are auburn or brown. Some species eat fungi, others feed on living crops or decaying plant matter. Some are attracted to carrion, others dung. Many are overlooked and insignificant, but some are grain and produce pests.
The spectrum of behavior and life history among Darkling Beetles is vast. Larvae are yellow-tan worm-like grubs. The commercially available mealworm is the larva of one particular genus in the Darkling Beetle family. Many species have chemical defenses as adults, spraying or secreting noxious solutions from their bodies. Some beetles are long and slender. Others have tapered abdomen or are round, like lady beetles. While all have wings, species in arid regions do not fly because their wings are fused shut, allowing them to prevent moisture from evaporating. The diversity of this family makes them fascinating to study.

Darkling Beetle (Family Tenebrionidae)

Salutations, BugFans,

Darkling Beetles

Darkling beetles are small-to-medium-sized, dark, slow-moving beetles in the family Tenebrionidae. Their elytra (the hard forewings wings that protect the flying wings), are often grooved and/or pitted, and as Lorus and Marjory Milne (under)state in the Audubon Society Field Guide to North American Insects and Spiders, the adults look like adults of a number of other beetle groups. The larvae resemble “wireworms,” the larvae of click beetles, of previous BOTW fame. The BugLady suspects that this darkling beetle is in the Genus Tenebrio, a cosmopolitan genus whose larvae are the famous “mealworms” that are sold in pet stores.

Both the adults and larvae are nocturnal scavengers on “dead” material like clothing, rugs, stored foods, and plant and insect collections as well as on rotting wood and fungi. Tenebrionidae is about the 5th largest family in the Beetle order, and the Beetle order is the largest group of anything. There are about 1,200 species of darkling beetles in North America mostly in the West. According to Eaton and Kaufman in Field Guide to Insects of North America, “Many discharge repulsive aromatic chemicals when threatened or handled.”

Now, about this “picture-keying” thing (trying to match the insect in front of you—or worse, an insect you saw three weeks ago—to a picture on a page). The BugLady does it all the time—but with a profound respect for its limitations. There are about 700 species of butterflies north of the Rio Grande, and about the same number of bird species. You can easily fit each group between the covers of a portable-sized field guide (except Sibley, of course). There are at least 100,000 species of insects in North America, which includes about 30,000 species of beetles in the beetle order Coleoptera.

Medium-sized black beetle? The BugLady’s favorite insect guides are the two listed above. Eaton and Kaufman picture about 2,300 species of insects, and Lorus and Marjory Milne show about 600. Considerably less than 1% of beetle species can be shown in the average field guide, and a whole bunch of those beetles are medium-sized and black and are spread throughout many families in the beetle order. So, you spot a beetle, and you open a field guide, and you start looking at pictures (BugFans can expand their picture-keying options exponentially at You settle on an exact match, and then you read the fine print and find that you’ve picked a beetle that’s found only in the simmering mud geysers of Yellowstone or the salt marshes of the Atlantic seaboard.

If you spot a picture of an insect that has a similar shape, color, proportions and range to the insect at hand, you might have chanced on the right family (the larger division above genus) or even the right genus. The genus and species arrangement of scientific classification—like Tenebrio molitor—is roughly like the sensible Chinese name order—last name first; first name last. “Smith John” tells us that this individual belongs to the larger clan of Smiths and is, specifically, John.

There are many insects that differ only minutely from others in their genus and do not even have common names. In some cases, identifying the insect’s family will be as far as you can go. Bottom line, the BugLady encourages picture-keying because looking at all those pictures opens us to the amazing diversity of insects and starts us on a path toward recognizing the characteristics of the different groups. Sometimes, you might truly have a “Bingo!” moment, but don’t mistake it for a “scientific” process. Caveat emptor.

The BugLady

Mealworm Farm Experiences

My mealworm farm adventure….
(Tenebrio molitor)
(also visit to see how Gallo del Cielo raises mealworms and to read about Amy’s mealworm farm.)
In the winter of 2010-2011, I spent $40.00 buying freeze dried mealworms for my girls since there were no insects available that time of year in Pennsylvania. My chickadees absolutely loved them and I was able to train them to come at the slightest call.
I found out that it was possible to raise mealworms without much trouble and went about the task of researching everything I could find regarding the subject. There seemed to be a lot of holes in the information that I found, and to some degree, conflict about it. So I decided to use the 3-drawer setup, which would enable me to ‘study’ the development and habits of the Darkling beetle and its different stages. My ultimate goal, though, was to store up enough larva to take my chickadees through the winter.
To say that I’ve had a blast is putting it mildly. I spent so much time watching and learning that I was even able to take photos of a beetle laying an egg. Really cool (well, it was for me!).
Probably the most important thing I learned was that temperature and lighting have a big influence on the speed of development. BUT, even though ideal temperature is reported to be 80°-100° F, a mealworm farm will develop very nicely at 72° F.
Okay, down to basics.
Life cycle Stages:
Darkling beetle
This time table is relative to conditions such as temperature, food source, etc:
Egg Incubation: 4-19 days (usually 4-7). Another source says 20-40 days. I had eggs hatch within 14 days of observation.
Larva: 10 weeks. Visible after about a week
Pupa: 6-18 (18-24?) days
Beetle and Egg Laying: 8-12 weeks (followed by death). Egg laying starts 4-19 days (average 12) after emergence. I now have beetles that are going on 5 months old. I am still finding eggs from this group, although not as many.
Pupae: Newly pupated to a few days old. The one on the far right is getting ready to morph into a beetle. Also 3 dead pupae at the top of photo.

Mealworm: One on the left just shed it’s exoskeleton so it is white.

Beetles: Again, the white one is newly morphed from a pupae. As they age they get darker….hense Darkling beetle! There are also a couple malformed beetles for reference.

Examples of deal mealworms and pupae. I had just cleaned my bottom drawer picking out the dead.

Housing: A simple aquarium or plastic bin will do as both have smooth sides. I have a 3-drawer colony and a bin colony. You will need to provide ventilation. To avoid the chance of other insects invading, I use screening material to cover the large holes we drilled in the lid and on the sides of the bin. Putting a screen over it also keeps curious cat paws out. Do not place in direct sunlight.
I have small holes drilled around the tops of each drawer in the 3-drawer colony for additional ventilation.
To make the 3-drawer setup, I cut the bottom out of the top drawer and hot glued screening material over the hole. This drawer is for the beetles so that when the eggs hatch, the small worms will fall into the second drawer. I found that a good number of the eggs actually dropped through also. I used the bottom drawer for the mealworms (larva) and moved them to the top drawer when the pupated. There they morphed into beetles and started laying eggs.

Substrate: The best substrate (substance to raise them in) is wheat bran (not the same as wheat germ). Rolled oats work, as does wheat flour and chicken feed. You can even add fish food flakes, dried milk and a wee bit of corn meal. From the research and personal experience, I will not use corn meal or chicken feed any more and I now freeze or microwave all food sources to prevent the possible problem of grain mites. It’s just a precaution but worth doing.
You’ll need at least 1-1/2” of substrate (if using a small set up like my 3-drawer). I’ve found that as the colony grows, it’s necessary to add more. I have about 4” in the single tub now, although I still maintain 1-1/2 in the 3-drawer colony. I have been thinning the numbers out (freezing them) as the worms get big enough.
Moisture sources: It is necessary to provide some sort of moisture source such as carrots, potato slice, apple slice, kale, lettuce, beet leaves, celery, dandelion leaves, squash slices, cucumber….you can pretty much try anything (except citrus). Either they will eat it or they won’t. It’s better if you only supply what they can consume in a day or 2 to avoid any chance of mold forming. You do not want mold in your mealworm colony.
It’s advisable to place the veggies/fruit on plastic lids or on bits of newspaper to prevent moisture from entering the substrate. Most of the problems encountered when raising mealworms is caused by too much moisture.
It’s good to provide cardboard pieces, egg carton pieces, toilet paper tubes, layers of newspaper or paper towel in your colony. The worms and beetles like to hide under and in these items. It also makes collecting them easier. The worms congregate under and in between the newspaper layers allowing you to pickup and shake them into another container or into your hand.
As a mealworm larva grows, it sheds it’s outer skin (exoskeleton) many times. After each shedding, the larva appears white. Newly hatched wee wormies are also white, as are the pupae immediately after they pupate and even the beetles appear to have an almost white body immediately after it morphs. As they age, all stages get darker. The beetle will generally darken until it is black.
Picture: Pile of shed baby exoskeletons. White larger worm that just shed it’s exoskeleton.

Picture of a beetle laying an egg. Picture of the egg beside a rolled oat.
You can slow down development by placing the larva (mealworm) in the fridge (I used clean cottage cheese containers with some substrate and holes punched in the lid) for quite a while. I did find that there was a higher mortality rate during pupation and higher deformity rate of the beetles from the refrigerated worms. It’s still a useful tool to stager the colony though.
At one point, someone raised the concern that the Darkling beetle is able to fly. Everything I read said otherwise. However, to put minds at ease, I conducted the “Do my beetles fly or not” test.
First test: Let robust beetles fall from height of 5′ into bathtub.
Second test: Let different group of robust beetles fall from height of 14′ into grass.
Findings: The Tenebrio molitor did NOT fly. Nor did it even bounce upon landing. *thunk* One of the beetles did OPEN it’s ineffective little wings but they didn’t even change the direction of its descent.
My newest setup:
I’ve been freezing mealeis from my original group and downsizing their housing as I go. I’m now setting up the single bin to accommodate 2 groups of beetles. I’ve been putting all beetles into a container for a couple months and plan to start a second container 11/10/11. This way, I can easily get rid of the beetles when they reach 5-6 months old..
I found 2 smaller containers to fit inside the single bin, cut the bottoms out and hot glued screening in. I then hot glued empty thread spools to elevate it above the substrate for the next batch of wormies!
The 3-drawer colony is still going strong with a new batch of wee wormies under way in the 2nd drawer. I’m still using rolled oats for the beetles and am sticking to a finer substrate for the worms to develop in to make sifting easier.
Also pictured is my pupae nursery. I’ve had more success moving the pupae into a small container with paper and a veggie leaf for a bit of moisture. I check the container often moving any morphed beetle into the beetle container.
I’ve found that not much space is really needed for a thriving colony so I’m sticking with the 3-drawer unit and my small single bin.


Are you thinking about growing your own mealworms?

Want to try your hand at starting your own home mealworm farm?

Mealworms are a healthy, nutritious snack full of protein. You can grow your own mealworms for a fraction of the cost and know that you’re doing your part in the earth-friendly farm-to-table movement.

What Are Mealworms?

Mealworms are the larval stage of the Darkling beetle insect. These critters are typically found in dark, dry places like flour or stored chicken feed. They extract the nutrition and water they need from the grain that they live in.

Adult female beetles can lay up to five hundred eggs during her lifespan of five to six months. After an average of twelve days, the eggs hatch into larvae known as mealworms. These critters will molt their exoskeleton several times before they reach the pupa stage at around three months of age.

Don’t be alarmed – the pupas might look like dead mealworms. While dormant, they are transforming into adult Darkling beetles. During this time, they do not eat. This stage will last for two to three weeks before hatching. Darkling beetles are brown for their first few days in their new form, but they gradually turn a black color. Their total lifespan is around five to six months.

Why Grow Your Own Mealworms?

I often joke that in the movie The Martian, Matt Damon would have been better off growing bugs instead of potatoes on Mars. In addition to being nutrition powerhouses and super sustainable, insects have incredible potential in urban farming. They take up very little space, can be grown virtually anywhere (with the proper setup), require less feed than traditional livestock, and do not consume much water. Efficient little machines!

Protein is one of the most expensive supplements to buy, so why not grow your own? There’s a reason why mealworms are a great choice for raising healthy chickens. And there’s no reason why we shouldn’t be eating them ourselves.

How To Farm Mealworms

If you don’t enjoy D.I.Y. projects, it is possible to buy mealworm farm kits online:

  • Livin Farms
  • Mealworm Breeder Kit
  • On Amazon too!

Step 1: Find A Container

The first step in building your mealworm farm is determining the container which you will use to grow them in. You can use a plastic storage tote, old aquarium, or . The recommended size is around 12 inches x 24 inches x 12 inches deep.

Your container will also need a lid or screen mesh to put over the top (make sure it allows for air circulation.)

If you’re a handy craftsperson and looking to build something a little more exciting, you can check out this guide on how to make a multi-tiered mealworm farm.

A multi-tiered farm might also be preferable because some suggest keeping the four stages of this insect (adult beetles, eggs, larvae, and pupae) separate. Adult beetles can dine on pupae or eggs.

Step 2: Prepare The Container

Make sure your container is clean and dry. You need to find a good location for the mealworm farm – somewhere dark/low-light and warm, ideally around 80 degrees Fahrenheit. In the winter months, you might invest in a heat mat like those made for reptiles.

Note: The ideal temperature to grow mealworms in is between 77 – 81 degrees Fahrenheit. Mealworms do reproduce in temperatures ranging from 65 – 100 degrees Fahrenheit, but temperatures above 86 degrees and below 62 degrees may negatively impact growth.

Step 3: Add The Feed

After the container is all set up, you need to fill it with feed (substrate) for your mealworms. You should fill the container about two to three inches deep with feed.

Many use wheat bran, rolled oats, chicken mash, or cereal crumbs for the feed.

When you’re growing mealworms for human consumption, stick with super duper clean feed. Wheat bran, rolled oats, dried grass, herbivore manures… just know what you’re feeding them. They get most of their moisture from vegetable scraps so put in peels and rinds from fruits and veggies like carrots, potatoes, cucumbers, apples, etc. Avoid fruits that will rot quickly and make your habitat moist. This is a no-mold zone.

Feed like wheat bran is not terribly costly, and you should be able to buy some for less than one dollar per pound It is important to sterilize the feed before adding it to the container to ensure that no pests are present. To do so, spread it out on a cookie tray and bake it in the oven for twenty minutes at 130 – 150 degrees Fahrenheit. After the feed is clean, add three inches of it to the container. Make sure that the feed is kept dry to keep a mold-free mealworm farm.

Step 4: Find Mealworms

You can buy mealworms online or at a local pet store. It is important to find a trusted mealworm supplier – especially if you intend to eat your mealworms. Like most insects, mealworms quite literally are what they eat.

I recommend:

  • Rainbow Mealworms
  • Rocky Mountain Micro Ranch
  • Wonder Worm Woman
  • Walden Worm Farm

Step 5: Add The Mealworms

Finally, you can add your little critters into your carefully prepared farm. As they say – the more the merrier! Aim to start with at least 500.

Gently pour your mealworms into the container and apply the cover (which exists to keep things out rather than to keep the mealworms in.)

Step 6: Feed The Mealworms

Now that the setup is complete, all you need to do is keep your farm fed and watch them multiply. You may feed the mealworms as much as you like – more food means more mealworms. Just be sure to feed them at least every few weeks to maintain a depth of around three inches.

Step 7: Harvest The Mealworms

In a few months (the complete lifespan from mealworm to Darkling beetle is five to six months) you can start collecting mealworms to eat. Make sure to leave the pupae and beetles in the farm to reproduce.

You will not need to worry about removing the dead beetles, as the larvae will take care of that for you. The only cleaning you will need to do is remove any bits of moldy food.

I’ve learned from some helpful sites (listed below) that one trick for easily collecting the mealworms is to add new feed. Place a vegetable such as a carrot into the container and leave it for five minutes. You will find that the mealworms will have latched onto the carrot. Now you may pull the vegetable out and shake it over a separate container to collect your meal…worms.

If you are fortunate enough to have more mealworms than you know what to do with, you can store extras in a freezer in plastic bags.

What To Expect When Growing Mealworms

Building a mealworm is inexpensive, can be completed in a matter of days, uses around 1.5 square feet of space, and can produce about 1 – 1.5 pounds of mealworms a week.

According to Instructables, here’s the timescale breakdown:

  • A Darkling beetle reaches maturity just a few days after it has emerged from its cocoon. During the 2 to 3-month lifespan, a female can lay hundreds, if not thousands, of eggs.
  • The egg takes between 4 and 19 days to hatch (average of 12 days).
  • It hatches as a tiny, whitish larva, which is hard to see at first.
  • The larva will go through several molts (up to 20), shedding its exoskeleton as it grows. The last molt occurs about 3 months after it has hatched from an egg, whereby it will be golden brown and between 1” and 1.4” long.
  • If you don’t harvest the mealworm at this stage, it will then pupate, encasing itself in a cream, hard case that doesn’t move much or eat.
  • After 6-18 days, a beetle will emerge. It will be pale brown and weak at first, but will darken to a black, shiny beetle after a couple of days, and the cycle can begin again.

I have no clever ending for this post… so happy farming! Would love to see any progress you make on Instagram! Tag @bugible – let’s be friends.


  1. The Happy Chicken Coop
  2. Instructables
  3. Sialis

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Incredibly Helpful Tips to Get Rid of Mealworms

Finding mealworms in the grain container is really disgusting! Mere sight of them makes you scream on top of your voice. What if you have their infestation in your house? Go through this post to know a few ways to get rid of these creepy creatures.

There are various kinds of pests found in our houses. Pests are unwanted guests in the house which we want to get rid of, as soon as possible. Mealworms are one such commonly found pest in homes. These crawly creatures are actually, not worms. A mealworm beetles life cycle consists of a larval stage. The crawling creatures we often find in our households, are the larvae of mealworm beetle which is scientifically known as Tenebrio molitor and is used to feed fish and reptiles. Mealworms have good commercial value, as they are used as fishing bait and act as a food source for other living organisms. Due to their commercial value, mealworms are raised in large numbers and sold off in the market to earn a fair amount of money.

Types of mealworms include lesser mealworm, dark mealworm and yellow mealworm. Each type has a different habitat. The type usually found growing in grain containers and spoiled food is the yellow mealworm. They are found to flourish in the dark, where the humidity level is high. That is why, these creatures often grow in closed grain containers and spilled leftovers of food. So, how do we get rid of them is the prime concern. Following tips might help you in case you have a mealworm infestation in your house.

Identify the Source

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Let’s Work Together!

Mealworms do not grow on their own. A potential source of their eggs might be responsible for the infestation in your house. Try to look for open nooks and corners that might be acting as an entry for these creatures in the house. If a source is identified, seal the opening to avoid further entry.

Dispose Infected Food

Mealworms are basically found to grow in food. It is essential to throw away the entire infected food because even after the removal of worms, their eggs might be left over which would later grow into larvae and eventually render it inedible.

Store Food in Airtight Containers

Using airtight containers for food storage is a great way to prevent the infestation. Airtight containers are tightly fitted and have no opening for the entry of mealworms. Zip lock packets are not so effective in preventing their growth as they are capable of piercing the thin plastic covering. Food items that are not used frequently can be stored in the freezer to avoid their unwanted growth as they cannot stand low temperatures.

Use Night Light in Dark Areas

Storage areas for food can be lit up using night light that would repel mealworm beetles, and stop them from depositing their eggs and larvae in the stored food containers.

Maintain Cleanliness in the Kitchen

Kitchen is most infected by mealworms as it has plenty of food source for them. Keeping the kitchen clean and dry helps in controlling the infestation. As they can lay eggs on decaying food or spilled leftovers, it is necessary to avoid garbage pileup by regular dumping of garbage. Frequent wiping of kitchen platform will keep your kitchen clean and fresh.

Collect Mealworms and Sell Them

As stated before, mealworms have great commercial value. If you really have a significant infestation at your home, try collecting them all and sell them in the local market. The collection might fetch you some money. Spreading a word through friends and relatives might help you in finding a potential buyer for your mealworms which you would otherwise throw away.

Contact a Professional Exterminator

If all this appears to be a difficult task, getting in touch with a professional exterminator will solve your problem. As they are trained professionals in dealing with any form of pest infestation, no one can do a better job than them in eradicating the mealworms from the house. A professional help definitely calls for an expenditure, but their service is worth the expense.

Regular use of pesticides surely help in driving away pests from the house. However, depending only on pesticides will not help in keeping the house free of pests. What matters the most is regular cleaning and maintenance of spaces which act as breeding grounds for these creatures. Hope this article has given you some idea about how to eradicate mealworms from your house.

Would you like to write for us? Well, we’re looking for good writers who want to spread the word. Get in touch with us and we’ll talk…

Let’s Work Together!

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Darkling Beetle Facts – Tips On Getting Rid Of Darkling Beetles

Darkling beetles get their name from their habit of hiding during the day and coming out to feed at night. Darkling beetles vary quite a bit in size and appearance. There are over 20,000 species of beetles called darklings, but only about 150 of them are native to the U.S. Darkling beetles damage garden plants by chewing off seedlings at ground level and feeding on leaves. Read on to learn more on how to identify and control these pesky insects.

Darkling Beetle Facts

It’s rare to see a darkling beetle in daylight, although you may occasionally find them running across the ground from one hiding place to another. They like to hide under bits of debris and clods of dirt during the day and come out to feed at night.

Many types of birds, lizards and rodents eat darkling beetle larvae, which are called mealworms. If you feed your pets mealworms, it’s better to buy them from a pet store or mail order source rather than collect them from the wild. Wild mealworms may be contaminated with insecticides or other toxic substances. The species you find in pet stores are bred specifically for animal consumption and have a high nutritional value.

Darkling Beetle Lifecycle

Darklings begin life as small white eggs under the surface of the soil. Once they hatch, the larvae (mealworms) feed for several weeks. They look like rounded worms, cream or light brown in color. The larvae shed their hard skin as many as 20 times as they grow.

After three to four months of feeding, the larvae crawl back into the ground to pupate. They emerge as mature beetles, capable of living 20 years or more if they manage to avoid becoming a meal for other animals.

Identification of Darkling Beetles

Darklings range in size from one-twelfth to 1.5 inches in length. They are solid black or dark brown and never have any colored markings. Their wings are fused together over their back, so they cannot fly. Their shape varies from nearly round to long, narrow and oval.

All darklings have antennae coming from the area near the eye. The antennae have lots of segments, with an enlarged segment at the tip. This sometimes gives the antennae a club-like appearance, or it may look as though it has a knob at the tip.

Darkling Beetle Control

Insecticides aren’t very effective at getting rid of darkling beetles. You should also be sensitive to the fact that when you try to kill these pests with toxic substances, you may also be poisoning the animals that feed on the beetles and their larvae. The safest method of getting rid of these pests is to eliminate their food sources and hiding places.

Remove decomposing organic matter and plants that have reached the end of their cycle promptly. Although darklings sometimes eat live plant material, most of them prefer decomposing matter. Besides eating garden debris, they also use decaying plants as hiding places.

Keep the garden weed free and remove weeds growing at the edges of the garden. Dense weeds serve as safe havens for darklings seeking shelter during the day. You should also remove stones, dirt clods and bits of wood that may offer shelter.

A darkling beetle adult and larva. (Photo by Kathy Keatley Garvey) Several years ago you probably read about the Stanford researchers who discovered that mealworms–larvae of darkling beetles–eat Styrofoam.

And if you attended the UC Davis Bohart Museum of Entomology open house on Dec. 5, 2015, you may have seen entomology student Wade Spencer showing visitors the larvae devouring his Styrofoam bicycle helmet.

And if you’ve been following the news from Environmental Protection Agency (EPA), you may have heard about the UC Davis doctoral student who just received a $15,000 grant in EPA’s National Student Design Competition for Sustainability Focusing on People Prosperity and the Planet (P3).

That would be Trevor Fowles, a second-year doctoral student in the UC Davis Department of Entomology and Nematology, who submitted his research project, “Beetle Larvae as Biodegraders of Styrofoam and Organic Waste.” He now has an opportunity to score a $75,000 grant in Phase 2 of the competition. He’ll be in Washington DC April 7-8 for the National Sustainable Design Expo at the Science and Engineering Festival.

Meanwhile, his 100,000 mealworms in the Briggs Hall lab of his major professor Christian Nansen, are munching up a storm (well, a blizzard of the white stuff) in a project that Fowles hopes will make a difference in breaking down Styrofoam–especially a problem in the nation’s landfills–and offer sustainable environmental solutions.

UC Davis agricultural entomologist Christian Nansen (Photo by Kathy Keatley Garvey) The larvae of the darkling beetle larvae, Tenebrio molitor, eat polystyrene or plastic foam, commonly known as Styrofoam.

“It’s about insects processing waste,” Fowles said of his research. “In three weeks they ate three-fourths of a pound of styrofoam, converting it into biodegradable waste.”

“Trevor’s project should be viewed as an example of what entomological agricultural research is all about in the 21st Century–developing new and highly innovative ways to recycle resources and more sustainable food production systems,” said agricultural entomologist Christian Nansen, an associate professor of entomology who specializes in applied insect ecology, integrated pest management (IPM) and remote sensing. In addition, the project has an applied evolutionary angle, which Fowles intends to explore.

“Our plan is to selectively breed insects and their microbial gut biome, so that they become highly adapted to breakdown, not only Styrofoam, but also different kinds of agricultural waste products,” Nansen said. “Similar to orchard growers bringing in bee hives during flowering periods for pollination, we envision that, in the future, companies will be able to order strains of insects for biodegradation of specific wastes. That is, the future of applied entomology will in different ways be about identifying and developing ways for insects to provide different societal services, including pollination, biological control, and biodegradation.”

The UC Davis research project involves designing a pilot-scale styrofoam biodegradation unit to take in regional Styrofoam and organic waste, and establish a high-performance beetle lineage, or the “best beetle larvae to do the job.” The adult beetles also eat Styrofoam, but not as much.

“Organization of our food systems will be a defining challenge in the upcoming century and I believe insects will play a significant role in transforming our agricultural sectors,” Fowles said.

The design emphasizes economic feasibility, community engagement, and environmental stewardship. To be sustainable, the project is aimed at connecting local community stakeholders with research expertise to produce an ecofriendly alternative for Styrofoam disposal.

After biodegrading the Styrofoam, the beetles can be pelletized for animal feed, Fowles said, and the excrement or frass can be used as “high-value amendment to compost mixtures.” He figures that that since Styrofoam by itself is a poor nutrient source for the beetle larvae, he eventually will mix it with organic waste materials, such as, pulp from wine and tomato industries, to optimize beetle development.

The darkling beetles and larvae are pests of stored grains, but the larvae are widely used throughout the world as food for humans; for captive pets, including fish, reptiles and birds; and as fish bait. They are reared commercially on fresh oats, wheat bran or grain, and often with sliced potato, carrots, or apple as a moisture source.

In the wild, darkling beetles and larvae are general decomposers, eating decaying leaves, sticks, grasses, and carcasses.

Fowles said he received his first colony of mealworms in 2016 from then graduate student Tom Nguyen at the Bohart Museum of Entomology (Nguyen is now a researcher at the Smithsonian Institution). Fowles purchased his 100,000 mealworms from the insect farm, Rainbow Mealworms and Crickets in Compton.

Fowles, who grew up in West Sacramento, received his bachelor’s degree in biology in 2011 from San Diego State University. Before entering the UC Davis graduate student program, he served as a lab manager for five years for Carroll/Loye Biological Research, launched by the UC Davis entomological team of Scott Carroll and Jenella Loye.

In a news release, EPA Administrator Scott Pruitt said: “This year’s P3 teams are applying their classroom learning to create valuable, cutting-edge technologies. This next generation of scientists is designing sustainable solutions that will help protect public health and the environment and ensure America continues to lead the world in innovation and science for decades to come.”

Fowles obtained his first colony of mealworms in 2016 from then graduate student Tom Nguyen at the Bohart Museum of Entomology, now a researcher at the Smithsonian Institution. Fowles purchased his 100,000 mealworms from the insect farm, Rainbow Mealworms and Crickets in Compton.

The project in the Christian Nansen lab is all good news for the environment. Who would have thought that beetle larvae would chow down on Styrofoam, the stuff that fills our landfills and what holds our coffee and take-out orders?

Stanford researchers say that every year we Americans throw away 2.5 billion plastic foam cups alone. And that’s just a fraction of the 33 million tons of plastic that Americans discard every year. Another statistic: less than 10 percent of that total gets recycled. And as a Stanford news release indicated “the remainder presents challenges ranging from water contamination to animal poisoning.”

Bring on the high-performance UC Davis beetles!

Basic information about darkling beetle

1. What do they look like

The darkling beetle is the name given to the largest family of beetles. They vary in size and lengths. There are more than 100 species of beetle and one of them in the darkling beetle. They increase up to 1.5 inches in length. The color of their body is black or sometimes brown. They do not have any other color on the body. These beetles cannot fly because their wings are fused back together. The shape of their body varies as some are round shaped while others are oval shaped. Their antennas are emerging from their eye. The larvae are similar to a worm, and it moves with the help of six legs. The larvae depend on the decaying leaves and sticks found on the ground. They have the ability to make tunnels through insulation and results in reducing insulation effectiveness. The male darkling beetle can be identified from its smaller mandibles and the antennae which look unique than other female ones. The female stag beetle can be identified by the full black color wings it has on its body. These species vary in size from 18 mm to 22mm.

2. What do they eat

Darkling beetles mainly depend on decaying wood and plants. They also live by eating plants and other little insects. The adult darkling eats leaves and the decayed plants under the soil. They do not drink water often because they extract moisture from every food they consume. They belong to the family of Tenebrionidae. The main diet of larvae can be cereal and flour. Nonetheless, the main diet is leaves and stems. They are also predator to other small animals such as fungus and weeds.

3. Where do they live

Many species of darkling are found in desserts and soil. About 100 of species are found in the United States, and they are also commonly seen in Jornada Basin. Most of these beetles are available in areas where the temperature is moderate with little rainfall throughout the season. Their species are also found in Norfolk, Yorkshire, and Lincolnshire. They know how to survive in cold temperatures. During the day time, they usually bury themselves in holes because of the extremely hot temperature. During the night time, they come out in search of food and water. Their wings are used to retain the moisture; this is the reason they are not able to fly.

4. What eats them and how do they avoid being eaten

Mites are the biggest predators of darkling beetles. When they see the eggs of beetles, they suck them and the larvae as well. They have their shell which they use to escape from the predator. Their biggest predators are reptiles, fish, and other birds. The predators usually attack the beetles when they are going through the mating process.

Five interesting facts about darkling beetles you may not know

  1. They do not need water on a regular basis; this amazing creature can easily survive without water. They consume water from every fruit they eat.
  2. There are above 400 species of darkling beetle found in the desert of North America.
  3. They have their shell for protection.
  4. These little species can bury themselves in no time.
  5. These creatures have the ability to produce a chemical spray called quinines, which has an atrocious odor and it helps the beetle to protect themselves from its predators.

Damage caused by darkling beetles

They mainly cause problems in wooden areas and poultry areas. They carry diseases which can be very harmful. If you have any decaying wood near your property, there are chances that they will lay their eggs and welcome more darkling beetles as well. In summers they multiply more quickly. The female can lay up to 2000 eggs in one year. They damage the wooden areas around your property. Many humans do not find them in a friendly way and don’t prefer keeping them as pets.

Darkling beetle control

There are several ways to keep control on the darkling beetle. Following are some of the most common methods.

1. Eliminate their food sources and hiding places

The first step you can take is to remove all the food resources. They are mostly seen hiding in decaying woods and soil. You need to check the places where the decaying woods and infected leaves are present. It will help you to eliminate darkling bugs from your property or nearby areas. These creatures tend to avoid bright lights, and they are mostly seen in dark places. So you can easily find them in dark and shallow spaces around the property. It also helps them to hide from their predators. These pests also lay their eggs in decaying wood.

2. Remove decomposing organic matter and plants

The main diet of darkling beetles is the infected leaves and stem. They are mostly seen living near the decomposing organic matters and plants. If you do not dispose of the infected leaves, it will give darkling battles living space. If you remove these, there are fewer chances for the darkling beetle to come and survive. The best thing you can do is clear all the trash and the decaying matters where you think battles are likely to present. They easily get attracted towards decaying and decomposing matter.

3. Keep the garden weed-free and remove weeds

You must weekly monitor the garden to see what is happening. You need to look for beetles in the litter around the garden. It is possible that they might dig up to 2 to 3 inches in the soil to bury themselves. You must remove the weed as it can become a place for the darkling beetles to survive.

How to use the best-selling repellent to get rid of darkling beetles

To get rid of these darkling beetles you can use organic repellents to stop their entrance. Some of these repellents may be expensive, but their results are very effective. If you think the trees in your garden or your property contains this beetles, then you must try one of the following repellents.

1. Termidor SC Termiticide

Termidor SC Termiticide is used to treat the pests in the affected areas. They eliminate the insects such as the darkling beetles by injection. They are the most effective non-repellent products which show 100% result. The product has a lower solubility in water and low odor, so it does not damage the underground soil or water. It is very easy to use and setup. The product is suitable for low-pressure power and ensures the pests do not return. The product is readily available online and in markets. You can also apply it to all the exterior walls and doors to eradicate these beetles. Unlike other insecticides, this cannot be felt by the insects. If you are looking for the best pest control pesticide, then this one is one of the best for you.

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2. Zenprox EC Insecticide

The target of Zenprox EC Insecticide is to kill all the insects such as the darkling beetles. They are specially designed for indoor use. The Zenprox will kill all the insects inside your property easily and quickly. It can be used with insect growth regulator as it prevents reinfestations. The product will help to save and protect your trees from the beetles. Each product is different from the other regarding features and working. This product is recommended for people who are in search of an effective pest controller. It will not let you down and help you in getting rid of beetles.

3. Tempo Ultra WP Contact Insecticide

It is the most efficient pest controller available on the market. It provides consistent results and fast action. Because the darkling beetle is commonly found in boiler and egg layer, they can easily be caught and killed. Although the prevention of these insects can be very difficult, it is not impossible. Tempo Ultra WP is considered as the most natural and effective pest control for your indoor as well as outdoor use. The product is specifically designed to kill all the beetles that are living in the decaying woods in your yards and gardens.


The darkling beetle has a vast variety spread around the world. They are small insects mostly found in the gardens and woods. They do not harm the humans, but they can be destructive in some areas. Their prevention in gardens and yards is very essential.

Darkling Beetle

Geographical Range

Tropical and temperate regions worldwide


Various habitats, including caves, forests, deserts, agricultural and urban areas

Scientific Name

Family: Tenebrionidae

Conservation Status


Many of the darkling beetle species and their larvae (called mealworms) are major agricultural pests. They feed on stored grain and are often encountered around livestock feed. They are also decomposers of dead plant material.

Some darkling beetles have an unusual defensive behavior. When they’re disturbed, they stand on their heads and run around randomly, earning them the name “clown beetles.” But because they also secrete a foul-smelling odor, they’re also called — you guessed it: “stink beetles.”

There are some 15,000 (!) species of darkling beetle in the world, and almost all are found in plentiful numbers in their various habitats. At this time, IUCN (an organization that determines species’ Conservation Status) lists just three species of darkling beetle: two are considered threatened and another is critically endangered.

Did You Know?

In North America alone, there are at least 1,300 species of darkling beetle. And that’s just a fraction of the number of all beetle species in North America: more than 30,000!

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