Yellow mealworm

Classification

Secondary pest; Fungus feeder and scavenger
Order: Coleoptera
Family: Tenebrionidae
Acronym: TMO

Description

• Adults are large (12 to 18 mm), dark brown or black shiny beetles
• Larvae are initially white, but as they mature they turn a characteristic yellow and reach a length of 30 mm at maturity.
• The yellow mealworm is the largest of the insect species that attack stored grain and grain products.

Similar species

• Dark mealworm (Tenebrio obscurus)

Commodities affected

• Prefers decaying grain or milled cereals that are moist and going out of condition
• Will also feed on products not out of condition: meal, flour, bran, grain, coarse cereals, bread, crackers, mill sweepings, meat scraps, feathers and dead insects
• Is occasionally found in bags of fertilizer, bales of tobacco, ground black pepper
• Is occasionally found in dwellings

Signs of infestation

• Damp and out-of-condition grain with larvae

Damage

• Damage is generalized and not readily identifiable as being caused by this insect pest

How to control

• Control grain insect pests

Geographic range

• Is distributed around the world and across Canada

Where found

• Prefers damp, old grain that has gone out of condition
• Is an indication of poor sanitation when present
• Is most often found in areas that are dark and damp: grain bins, sacks of feed, mills, elevators, feed plants, warehouses and in the litter of domestic fowl houses

Life history

• Adults appear in early summer.
• Females deposit eggs singly or in clusters in the food or on the sides of bins.
• Females lay 300 to 500 eggs.
• Larvae are resistant to dry and cold conditions and can survive up to 3 weeks at temperatures of -15°C, but prefer 25°C and moist conditions.