Indian meal moth adults have a 5/8” wing spread. The wings are a burnished copper; almost purple in colour with a broad grey band near where they attach to the body. The larvae are small caterpillars with distinct legs on the first three body segments and four pairs of prolegs (false legs) on the abdomen. They are dirty white, pink, brown, or light green, and range from 3/8-3/4” long. The head and first body segments are brown.
These are one of the most common stored product pests found in homes and food processing institutions, as well as grain storage and processing facilities. The larvae prefer to feed on coarsely ground flour and meal, but also are commonly found feeding on whole grains, dried fruit, nuts, chocolate, beans, crackers, biscuits, dehydrated dog food and red peppers. The larvae produce webbing over the surface of the materials on which they are feeding that is filled with their frass (feces). The damage caused by the insect’s feeding is compounded by the presence of this repulsive mat.
The insects usually overwinter as larvae. The adult females lay their eggs at night on larval food, producing as many as 400 in 18 days. The larvae move into cracks and crevices within the food material, feeding within or near the silken, frass-laden mat they produce. Mature larvae often move away from infested materials to pupate in cracks or crevices. This behaviour pattern often allows them to be discovered by homeowners. There are usually 4-6 generations per year depending on the food supply and temperature conditions.
The source of Indian meal moth infestations in homes and other locations must be discovered and eliminated by disposal of the infested materials. The presence of the silken mat usually ensures that infested materials are discarded. The surfaces, cracks, crevices and other potential harbourage areas can be treated with a residual insecticide. The use of a glue trap with a pheromone is also useful.