Origin:
Possibly European in origin, but now found throughout the world. The yellow mealworm is found in the U.S. primarily in the cooler northern states, and a related species, the Dark Mealworm, is found throughout the country.
Biology:
The name of this species is given to the appearance of the larva, which is an elongate, shiny yellow worm. The winter months are usually spent as the larva, with progression to the adult in the spring. Adults live for only 2 or 3 months, with one generation per year. Over a period of several months the female can lay between 275 and 460 eggs, usually in the food material the larvae will eat. The larvae usually take around 600 days to completely develop through their 15 molts, and a complete life cycle commonly takes 2 years. The larvae of mealworms are commonly sold as fish bait or as food for pets such as lizards or fish. They often infest food materials in less than good condition, particularly moist, slightly deteriorated products, and the long life cycle suggests that food products that are infested have been in storage a long time. They may infest most grain-based processed foods.
Identification:
Larvae are over an inch long and are thin and cylindrical, and shiny yellow with 3 pairs of legs at the front. They can be very active in their mobility. Adult beetles are the largest of the stored food pest beetles, being over one half inch long, a dull black to dark brown, and elongate. The elytra (front wings) are hard shells that completely cover the abdomen and join very closely with the prothorax. The adults are not capable of flight.
Characteristicts Important to Control:
Proper stock rotation to inhibit development of the larvae is important, along with good storage practices to keep products dry and cool. Disposal of infested materials is appropriate, and people have been known to become infested with the larvae they have eaten in infested foods, although no particular health problems have resulted.
