These beetles differ depending on the species. There’s a lot of diversity depending on the origins and local environment of the beetle.
But the common mealworm beetle found in the US in the pet trade and poultry farms has the following phenotypes:
Elongated ovular body
Horizontal segments running down the outer elytra
3 segmented sections
Pair of orange antennae (red or black possible)
6 visible legs
2 dark eyes on the head segment
11 segments on the antenna
Eyes notched by a ridge
Tarsal claws
12-25mm
Hard exoskeleton
Compound eyes
How do you tell if a darkling beetle is male or female?
The difference between male and female darkling beetles is difficult to tell because of their microscopic features.
But you can try if you look for the following sexual dimorphisms:
Females have no separation between the three posterior sternites, males have a visible lighter coloration dividing the sternites at the rear
The 5th sternite is pointed in the female and round in the male
Females are generally bigger
Life cycle
The mealworm is not a worm. It’s a larva of the adult beetle.
Even though the name implies that it’s a worm. It’s not.
The larvae of the darkling beetle have six legs behind the head and feed on detritus until it’s ready to undergo metamorphosis.
Each mealworm will molt several times and shed the outer exoskeleton over time.
When it enters the pupa, it’ll begin pupation which lasts anywhere from 2 weeks to 10 months, depending on local conditions such as temperature and food availability. When pupation is complete, the adult darkling beetle comes out and mates.
Eggs will be deposited and take about 5-20 days to hatch, again depending on temperature.
Each female can lay hundreds of eggs. The eggs are small, white, and oval-shaped with a 2mm length.
What are darkling beetles good for?
Because they’re scavengers, these beetles are beneficial in the sense that they help decompose waste products.
They’re also commonly bought in the pet trade as a nutrient-dense food for reptiles like snakes and lizards and even fish.
They’re a favorite among pet owners because of their low maintenance, easy growth, and no odor/noise production.
In nature, they help recycle waste products like rotting stumps and logs. They consume debris and plants and are a necessary part of the lower ecosystem.
Are darkling beetles harmful? Do they bite?
A darkling beetle found in the southern US with a less popular patterning.
No, darkling beetles don’t bite nor do they carry any toxins such as cantharidin.
To humans, they’re completely harmless in terms of bites.
That’s why they’re often kept as pets. These beetles may sound scary, but they’re not. They’re just a nuisance when you find them crawling around on your carpet, bed, or dry food.
But here’s something about them you should know:
Even though the beetle itself poses no danger, they DO tend to crawl around and feed on organic matter.
If you have a poultry house that houses chickens and other birds, these beetles are attracted to the waste matter and will feed on it.
They can then come into your house or crawl on surfaces and transmit bacteria and virus vectors from the decaying organic matter they crawled on earlier.
They’re also extremely common in poultry farms and facilities because they provide these pests with plenty of excrement to eat.
They’ll burrow through feces, sticks, grains, grass, and other organic matter.
Darkling beetles also feed on poultry blood- they bite through the skin of chicken, birds, ducks, and more to feed on the nutritious blood within.
Because they’re so filthy, they carry a few different diseases with them and transmit them to poultry and humans.
Some of the identified bacteria, viruses, and other nasties transmittable from beetles to humans are:
Newcastle
Fowlpox
Avail influenza (bird flu)
Salmonella
E. coli
Campylobacter
Clostridium
Tapeworms
Roundworms
Enterovirus
Rotavirus
Eimeria
Coccidiosis
Lastly, darkling beetles are also destructive. They chew through wood and other insulation structures.
Their chewing and burrowing can destroy your home’s structural integrity over time- just like termites.
This can pose a threat for stairways, steps, and even the very foundation of your home if you’ve got a serious beetle problem.
Do they smell?
Darkling beetles do emit a foul odor when disturbed.
When you threaten or provoke them, they’ll start to stand up on their heads and put their rear end in the air.
This will release a smelly odor that makes them not as tasty to predators. You should avoid disturbing them when possible if you don’t want to smell the odor.
Can darkling beetles fly?
Some do. Most don’t.
Darkling beetles are a group of beetles rather than a single species. The majority don’t fly due to wings that are fused to their body- also known as elytra.
There are over 20,000 species, so it’s not easy to identify which species can fly or not.
But other darkling beetles do have the ability to fly with working wingspans. If you find darklings flying around your house, or more commonly, the chicken coop, these are indeed flying beetles.
But the ones you buy in the pet store that turn into mealworms can’t fly. It depends on the species and its origins.
Here’s an easy way to remember:
Mealworm beetles never fly.
The majority can’t fly.
But there are a few that can (poorly).
Even with the ability to fly, it doesn’t matter if you don’t plan on keeping them as a pet. They’re terribly flyers and will only do so when foraging for food.
If you provide them cover and something to eat, they rarely will fly out of the immediate area.
Some people notice that the darklings infesting their property never fly, but then out of nowhere, they suddenly fly. This is because even some species can, they’re bad flyers.
You’ll find them running into the ceiling, objects, and walls only to tumble back down. So they’re easy to kill and catch.
Are they nocturnal? When are they active?
Darkling beetles are nocturnal creatures, which means they only come out at night. It’s rare to see one during the day.
But if you do, it probably means that it was disturbed or is foraging for food or water.
They also may be scouring for a hiding place and using the debris to hide as they seek shelter.
But most darklings will only come out at night to feed.
This is a strategy to protect themselves from predators in the daytime, such as birds, small animals, and other predatory insects that feed on them.
Beetles have extremely high nutritional profiles so they’re a tasty treat for preying predators that eat them.
Thus, they’ve evolved to only become active at night when most threats are asleep.
Do darkling beetles make noise?
No, not particularly.
You may notice a slight scraping noise as they try to climb on slippery surfaces like plastic or glass, especially if there are a lot of them, but otherwise, they don’t have any body parts that emit noise unlike grasshoppers, cicadas, or crickets.
Darkling beetles can also bump their body against surfaces, which can also emit a low thump.
But you’ll likely never hear it unless you have an amplifier or something. This is why many hobbyists who keep reptiles, fish, or other pets raise darklings/mealworms.
They’re easy to keep and make no noise at night.
How to get rid of darkling beetles in the home naturally
Darkling beetles can be controlled using some DIY techniques you can do at home.
Darkling beetles require a combination of mechanical and biological control.
Poisons and insecticides also may be used but should be avoided around the home or if you’re growing edible vegetation.
These pests can quickly breed and grow to numbers difficult to quickly control and this is why you should start right away.
Use a combination of the following home remedies for the most effective and efficient control.
Don’t rely on a single method as you’ll often find that it works best when combined with other solutions.
Get rid of their food source
Their food source is their primary reason for being inside your home, garden, chicken coop, or wherever else you see these beetles.
Get rid of it completely and you’ll no longer have any problems with them. You must thoroughly examine the areas of infestation and find out what they’re eating.
Because they feed on a variety of different things, it can be difficult.
However, once you find it and remove it, these beetles will hang around for a bit only to discover that they no longer have a sustainable place to live. Then they’ll migrate away.
Finding food is the hard part.
Here’s a list of common things darkling beetles eat:
Bran meal
Oranges
Cucumber
Apples
Romaine lettuces
Pears
Decaying organic matter
Feces
Plants (leaves, buds, stems, etc.)
Carrots
Cereal
Flour
Fungi
Dry goods
Pasta
Animal matter
Fresh plants
Darkling beetles are scavengers, so they eat whatever they can find. They’re not particularly picky about it and will feast on just about any organic matter.
This is why you need to keep your home and garden 100% clean. They can live off of the smallest waste products and scraps whether it’s from your table, trash can, recyclables, or even Fido’s poop.
Did you ever notice that the more waste there is, the correlation to the beetle population is proportional?
The more food that’s available, the bigger population of darkling beetles. They’ll breed and reproduce based on food availability.
So if you get rid of the food or greatly reduce the availability of food, their numbers will drop significantly.
Remove hiding places
Pests in barnwood can be difficult to control.
Getting rid of their hiding places is just as important as removing their food sources.
Beetles need somewhere to hide during the daytime so they feel safe and secure from predators.
Unfortunately, this also means that you’ll have to do some thorough examinations of your property to find and destroy their shelter.
Darkling beetles need a source of water to sustain themselves.
Although they can go for weeks without any food or water, they’ll eventually need to drink. If you remove all sources of water regularly, they’ll eventually be forced to leave because there’s no moisture to thrive.
Necessary hydration is important for beetles because they molt. This is necessary to grow bigger. Both the larvae (grubs/worms) and the adult beetles need water.
Remove all sources of liquids in your kitchen to reduce the number of beetles. This means doing basic cleaning and removal of water after washing your hands, dishes, etc.
Water spills should be cleaned right away. The same goes for other areas where dry goods and water are within reach, like chicken coops and poultry farms.
Also, check outside your home for plumbing and leaks.
Prevent wet spots and puddles from forming under water spouts, sprinklers, drainways, etc. Water will attract different pests like mosquitoes, plaster bagworms, and thrips.
If you find stagnant water, clean it up right away and repair or patch whatever is supplying the water for the darkling beetles.
Keep your garden clean
A clean yard proves to be less attractive to pests.
Keeping your yard clean is crucial to maintaining a bug-free yard.
This means doing all the basic maintenance you’d be doing if you were the perfect homeowner (if that exists)!
Regularly scheduled cleaning will help keep your home free of pests because the garden is usually where bugs first take notice of a suitable environment for them to thrive.
Keep bird feeders, poultry feed, pet food, etc. out of reach
Get rid of water features or keep them maintained
Sure, it’s not always easy to do all this work. And you’ll probably spend a good weekend or two fixing up your yard.
But once you get it going, you’ll find that it’s a lot easier to care for with scheduled cleanings here and there.
If you’re busy (like everyone else), consider hiring a professional landscaper or gardener to keep your yard clean.
Check for bird’s nests
Bird nests are often sites for beetle problems.
If you see beetle activity, check around your property for bird nests.
Mealworms are sometimes found in the nest of birds as they’re carried quite the distance back to the nest. If you find any in your loft or soffits, remove them.
They can often be a source of mealworm beetles if you suddenly see them in your home out of nowhere.
Build a DIY light trap
A light trap can be a useful tool to catch beetles passively and monitor their numbers over time.
There are tons of different designs you can look up online, but generally how it works is that it uses a glowing light source that is left on overnight to attract beetles. As they walk towards the light, they fall into a trap and can’t get out (like a funnel).
You know what I’m talking about. The infamous inverted water bottle trap. Here’s how to make one:
What you’ll need:
A water bottle (2-liter or standard 16-ounce bottle)
Scissors
Tape
A weatherproof light (battery powered is easier)
Petroleum jelly
A small garden spade
This is how you catch a darkling beetle.
How to make it:
Take the scissors and carefully cut the top ⅓ of the bottle top off.
Invert the bottle top and shove it into the bottom ⅔ of the bottle. You should now have a funnel that goes into the bottle.
Line the edges of the bottom ⅔ of the bottle with petroleum jelly. This will prevent the darkling beetles from escaping once trapped.
Tape around the neck so it’s secure and the two pieces are stuck together.
Get your spade and start digging. Dig out a small narrow hole that fits the bottle into it up to the soil level. The top funnel should be right on the surface level of the surrounding soil or substrate.
Take the weatherproof light and point it directly into the bottle. Leave it on overnight. Make sure it’s weatherproof and your wiring does not pose a hazard (if you’re not using battery power).
How it works:
The beetles come out at night and walk towards the warmth of the bulb.
They fall into the funnel and can’t get out.
You can monitor what types of beetles are in your yard, and check to see if your DIY remedies are working or not.
Over time, you should see fewer bugs getting trapped if they’re working.
Set up multiple traps around the yard to see what area has the most beetle activity.
Empty the traps and clean as needed.
Or try building a PVC trap
A PVC trap works the same as the bottle trap mentioned prior. The way it works is to bait them out by using corrugated cardboard.
Darkling beetles are attracted to rolled cardboard with the miniature “tunnels” they can sandwich themselves between to feel safe.
Roll a tube of corrugated cardboard and put it inside the PVC pipe. It should be about 2” in diameter across and any length you wish. The longer the roll of cardboard, the more beetles you can trap.
Place the trap wherever you suspect beetles to be active. Check them every week for beetle activity.
This isn’t meant to eliminate the beetle infestation. It’s more of a device to gauge the population over time. Use it to gauge the effectiveness of your efforts.
Don’t recycle the same cardboard. Use a new piece each time.
Drop the temperatures below 45F
The cold temperatures can passively kill both the larvae and adult beetles simultaneously.
Darkling beetle eggs will perish when the ambient temperature hovers around 45F.
This can be extremely beneficial if you have darkling beetles in an outdoor barn, shed, or outhouse.
If you’re in a colder region, let the temperature drop below 45F and it’ll kill all the beetle eggs.
This will instantly stop their lifecycle and you can expect to see adults and nymphs scavenging for cover, but no further beetles will be bred. Remove all food and water during this time to completely disrupt their behavior.
Chicken litter is especially important if you have them on an outdoor poultry farm.
A temperature under 30F kills adults, all beetles, regardless of egg, larvae, nymph, or adult. You can shut off the heaters during a cold snap to wipe out the beetle population.
Sprinkle boric acid
Boric acid can be used to control beetle activity.
Boric acid can be a practical, cheap, and effective way to control darkling beetles.
Boric acid will dehydrate beetles when ingested. Mix in the powder with their food source.
Upon eating it, the beetles will die shortly after from the microincision it makes inside their body.
The sharp crystals also cut up their exoskeleton on the outside. Keep away from pets and humans. Water and wind may reduce the efficacy of the powder.
You can dust the most common parts of your home also to help deter them. The fine powder gets into cracks and crevices easily where traps and sprays aren’t practical.
Use it wisely and use it as directed.
What eats a darkling beetle?
Beetles and mealworms have PLENTY of predators.
You can lure natural predators that eat darkling beetles if you already have them in your area.
If you presently have any of these predators, they may be beneficial to help bring down the populations of beetles.
Of course, you’ll need to learn how to attract them to your yard first.
Find out which ones you’ve seen natively hanging around your property and then do a search on how to bait more of them to your yard.
How do you kill darkling beetles?
Before you ask how to kill them, you should ask:
“Should you kill these beetles?”
Darkling beetles rarely are a serious problem unless you ignore them and let their population spiral out of control to the point where they take over your yard.
Many people consider darkling beetles to be a beneficial insect because they help clean up rotting carcasses and other decaying organic matter.
Farmers also recycle compost and waste piles that can help reduce odors and other pests from coming to their crops.
These beetles are at the bottom of the food chain because they focus on waste products from other species, which will eliminate the food of other insects that feed on feces.
This also makes them extremely common in areas zoned for agriculture, like farms and barns.
However, if you’re recycling compost or manure, these beetles can be an annoying nuisance as they’ll show up all over the place and be extremely difficult to completely eradicate.
But that’s why you decide if you want them or not before you let them eat everything you try to mulch or recycle.
So depending on your situation, you may want to kill some of them but not all so they can help stop other bugs from coming.
If you decide that you want to eradicate them, use a combo of the techniques listed on this page plus a commercial IGR if necessary to fully and completely kill these pests.
How to get rid of darkling beetles in chicken houses
Chicken, turkey, and duck farms often have darkling beetle infestations.
You’d think these beetles are just passive scavengers, but that’s not always the case. They’ll be glad to attack weak poultry because they’re an easy target.
Using darkling beetle insecticides
You should avoid using any dangerous or toxic compounds, sprays, and pellets when possible. Insecticides don’t work well against beetles in general.
And if they do, they ingest the poison into their system, which poses a danger to anything that eats them. Since they’re a delicious meal, many beneficial species feed on them.
You’re indirectly getting the toxic compounds into birds, small animals, and even beneficial insects.
Plus, some of those compounds are bad for humans and pets.
Do you want lingering spraying around your home? Avoid when possible.
But if you must use a store-bought, commercial insecticide for darkling beetles here’s what to look for.
Commercial solutions
There are a lot of different products on the market aimed at controlling beetle infestations around your property.
If you need to resort to commercial-grade solutions, usually a two-pronged approach of an insecticide spray with an IGR does the trick.
Again, if you grow edible fruits or vegetables outside your home, avoid using toxic compounds if possible. You don’t want to spray these chemicals everywhere because of obvious reasons.
For an insecticide, look for something that contains Clothianidin, permethrin, pyridine, or a bacterial host-specific pathogen.
Find something utilizing an IGR, which is a compound that helps control darkling beetles for an extended period.
There are liquid concentrations and dust applications. Use as directed.
An IGR (insect growth regulator) can help prevent darkling beetles from breeding and completing their lifecycle. It’s a quick fix. Sprays that contains IGRs stop the cycle and disrupt them from breeding.
Most IGRS contain synthetic compounds which should be avoided if you plan on spraying or applying on your edible crops. Avoid if you plan to have kids or pets (or people) in the area. Don’t eat crops sprayed with IGRs unless the label says it’s safe for consumption.
But even then, I’d be wary.
Some of the notable names are:
Darlex
Tempo 1% Dust
Rabon 50WP
Cyonara 9.7
Credo SC
Use as directed. Use common sense. And wear your PPE.
Further reading
Here are some additional references you may find useful:
Currently an active researcher in the pest control industry for the past 8 years- with a focus on using natural and organic methods to eliminate pest problems.
I share handy DIY pest techniques I come across here to help out others (and possibly save them from a mental breakdown).
Please email me back