Though the name can be misleading, mealworms are darkling beetles, a large group of beetles made up of many species. Two pest species of mealworms, yellow and dark are found throughout Canada. These insect pests surprise and disgust homeowners when they discover them in stored food products.
Mealworm adults are relatively large beetles measuring about 12 to 15mm long with dark brown to black shinny bodies. The larvae look like tiny yellow caterpillars and can grow up to 30mm at maturity with very hard shell-like bodies. Yellow mealworm beetles are a deeper brown than the dark mealworm species and the dark mealworm larvae has dark brown ring-like markings on the upper and underside of the body.
The pests prefer dark, damp spaces where old grain is present. They are commonly found in farm facilities and grain handling facilities or inside sacks of livestock feed. They typically find their way into homes while sealed inside packages of processed grains.
Mealworms feed on decomposing grain that is damp and moldy. The pests also feed on meat, dead insects, and dried fruit. Homeowners may find these insects in oatmeal, flour, and other milled, starchy foods.
Female mealworms lay 400 to 500 eggs at a time. The eggs hatch into larvae in about two weeks’ time and remain in the larval stage for about three months before pupating and passing the winter and emerging as adult darkling beetles in warmer weather. Insects in any of these stages of development may infest food in homes.
Problems Caused by Mealworms
Mealworms are minor pests of stored food products however they should be taken seriously and dealt with quickly. If the larvae or eggs are ingested with food it can cause gastrointestinal irritations. Mealworms rarely cause any damage to houses aside from consuming and contaminating pantry goods. Flour infested by the pests sometimes emits a strong odour and contain waste, skins, and other debris that make it inedible. The presence of these insects can be a sign of poor sanitation.
Detection/Signs of Infestation
These pests are large and visible. Recognizing both larvae and beetles is important in removing them from homes and pantries.
Homeowners can prevent mealworm infestations by keeping food products, especially grain products in good condition and moisture free to prevent mold growth. Inspect stored products regularly. Dispose of any overstayed or spoiled food products and any infested product. Proper sanitation will also help keep mealworms out of homes.
First, locate the source of any infestation that is the mealworm problem, checking for old milled products and moldy foods. Remove and dispose of the products and vacuum the surrounding counter, floor, or cabinet space. Sanitize the area to get rid of any bad smells. Complete removal may require the assistance of pest professionals.