Lesser mealworm
Alphitobius diaperinus (Panzer)

Order: Coleoptera
Family: Tenebrionidae
Acronym: ADI

Ecology

The lesser mealworm is worldwide in distribution. This insect is widely distributed in Canada and thrives in damp and mouldy conditions. It is a scavenger and feeds on fungus and is not usually found in clean sound grain. In Canada, it overwinters in heated storage and is not likely to survive harsh winter conditions. Adults and larvae are often found to occur in poultry house litter, and in animal barns where they feed on feces and dead animal carcasses. It is most similar in appearance to the black fungus beetle, Alphitobius laevigatus.

Damage

Lesser mealworm damage is not distinctive. The adult and larva are general feeders usually found in damp environments feeding on grain that is spoiled or out of condition. Both the larva and adult feed on broken grains; wheat, cowpeas, barley and rice. In poultry houses, heavy infestations of lesser mealworms may spread poultry diseases. Heavy infestations of larvae may occur in the walls of poultry and animal housing by burrowing into wall insulation. A sign of infestation is a disagreeable odour in the commodity. The presence of lesser mealworms indicates that conditions are favourable for the establishment and development of other pest insects.

Life history

The adult is reddish brown to black. It is 5.5 to 7 mm long. It is oval shaped and the pronotum is flattened. Adult lesser mealworm can be distinguished from adult black fungus beetle by the shape of the eye. The lesser mealworm eye is 3 or 4 facets wide at its narrowest point when viewed from the side. Viewed from the side, the eye appears divided. The adult is long lived. If temperatures stay between 21°C and 34°C, the adult can live for 400 days. Adults can fly.

The female lays eggs in clumps and sticks the eggs to the food material. The female will lay on average 4 eggs per day for her life. About 300 eggs are laid during a lifetime.

The larva is yellow-brown and is cylindrical in shape. It is active. It constructs a pupal chamber in the commodity and will pupate there. Development conditions range between temperatures of 25°C and 35°C and a relative humidity of 80-90%. In these conditions, development can take as little as 35 days.

Control

• Manage feed stocks
• Fumigate the empty structure
• Remove infested insulation.

Controlling insect infestations

Images

Adult: Lesser mealworm - Alphitobius diaperinus

Natasha Wright, Florida Department of Agriculture and Consumer Services, Bugwood.org
Adult lesser mealworm

Natasha Wright, Florida Department of Agriculture and Consumer Services, Bugwood.org
Lesser mealworm - side view