Size: Larval mealworms usually measure between ⅛-1 inch long with ½ inch being the average.
Color: Adults are dark with a hard shell. The mealworms themselves (larval form of the beetle) are yellowish-brown with ringed, segmented bodies. They may look darker near the ends of their abdomen and head, and near each of their grooves or segments.
Body: Mealworms have evenly divided grooves resembling body segments running along the whole length of their abdomen.
Mealworms leave behind bite marks and small holes in packaging for stored dry goods. You may find signs of damage or tampering on cardboard or other food packaging, particularly in dry storage which indicates a mealworm infestation.
When mealworms eat through packaging, they often produce a distinctive dry, paper-like waste. This waste looks somewhat dusty. You may find it both outside and inside of food containers.
Scientific Order: Coleoptera
Common Species: Tenebrio molitor, or Yellow Mealworm, the larval form of the mealworm beetle, a species of darkling beetle.
Your first step toward preventing mealworm infestations is removing potential shelters or food sources. Remove decaying material such as fallen leaves, compost, or old vegetation away from the perimeter of your home or building. Next, keep an eye on all your cabinets, closets, and storage areas, especially where you keep food and other dry goods. The ideal mealworm infestation site is dark, humid, and warm, so look for the pest especially carefully in basements, warehouses, attics, and pantries.
Remove any mealworms you find using a vacuum and throw out the food they infested immediately. If you find mealworms, check nearby food sources especially carefully as well. Recheck any damp, dark spaces for signs of mealworms periodically even after treating an infestation thoroughly.
Mealworms typically feed on anything they can find that is damp, decomposing, or moldy. They’re particularly fond of dead leaves, foliage, animal waste, and moldy or moist grain products. They’ll frequently infest pantry items like oatmeal, flour, cereal, oats, and other dry goods.
Mealworms feed continuously, stopping only to shed their skin, or molt. As they feed, the larvae use their hardened heads to push and tunnel through food. Once inside the food, mealworms may be hard to spot at first. Fully-grown beetles lack the ability to burrow but gain the ability to fly and release a foul-smelling chemical from a scent gland. They’ll produce this foul scent whenever they’re disturbed or threatened.
Mealworm beetles go through four developmental stages: egg, larva, pupa, and adult. The length of each developmental process depends on the temperature of the environment and how readily available food is. Their typical mealworm life cycle is between 3 and 12 months.
A single female mealworm can produce over three hundred small, white, bean-shaped eggs at a single time. Larva hatch from eggs in 18 days or less and begin eating, moving, and infesting food products immediately. Mealworms may stay in their larval stage all winter if temperatures are too low. Otherwise, they’ll eat and grow continuously, shedding their skin multiple times until they’re fully grown. Adult beetles grow wings, which they use to seek out new mates.
“UMaine Cooperative Extension: Insect Pests, Ticks and Plant Diseases.” UMaine Cooperative Extension Insect Pests Ticks and Plant Diseases, https://extension.umaine.edu/ipm/ipddl/publications/5044e/.
“Mealworms.” Mealwormcareorg, https://mealwormcare.org/.
“Mealworm.” Mealworm | Horticulture and Home Pest News, https://hortnews.extension.iastate.edu/mealworm.
A mealworm is the larval stage of a flour (or mealworm) beetle.
Anything damp, rotten or moldy. They will eat decaying leaves, plant matter, other insects and dead animals. In your home they will gravitate towards cereals, grains, seeds and pet food.
Yes. Mealworms can digest both polystyrene and polyethylene – plastics commonly found in bags, bottles and containers. Not only can they digest these plastics, they remain a safe, protein source for other animals. Some see mealworms as a solution to the plastics problem however, it takes 4,000 worms a week to eat one Styrofoam cup.
In the wild, mealworms live in leaf litters, under rocks and logs or in animal burrows. They enter your home through small holes and cracks around your foundation.
Yes. Mealworm larvae molt (shed their skin) 10-14 times before they pupate into their final adult beetle form.
No. They may startle you, but mealworms are not dangerous to humans. Many pet owners feed mealworms to their reptiles and rodents. Mealworms have also been approved as a safe food source for humans, so go ahead and bite them.
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