August 1996
SIZE: 1/2 to 5/8 inch (12-15mm)
COLOR: Yellow or dark depending on type
DESCRIPTION: The yellow mealworm (Tenebrio molitor) and the dark mealworm (Tenebrio obscurus) are very similar in appearance. The adults are large beetles, 12-15mm in length. The adult of T. molitor is dark shiny brown to black; T. obscurus is a dull black. The larvae resemble wireworms and are familiar to many people as dried food for aquarium animals.
HABITAT: In cabinets and pantries where cereal foods are stored.
LIFE CYCLE: Eggs are laid singly or in clusters during the spring. Each female lays about 275 eggs which hatch in 4 to 14 days. Larvae may spend up to two years in this stage depending on the environment. Most larvae mature by fall and pupate in the spring, with the pupal stage lasting 7 to 24 days. Individual larvae may wander far from the food source to pupate, causing homeowners difficulty in locating the source of infestation.
TYPE OF DAMAGE: Infest cereal foods.
CONTROL: Controlling mealworms requires carefully inspecting all cereal foods, discarding the heavily infested material, repackaging material in new containers, and vacuuming kitchen cabinets.
INTERESTING FACTS: Yellow mealworm larvae are known as "golden grubs" and make excellent fish bait. Although these insects are world-wide in distribution, they are rarely of major importance.