The caterpillars of several moth species are pests of wool and silk, while other species infest dry foods, such as flour and cereal products. It is the caterpillar that feed on and damage products; the adult moth searches for new sites to lay eggs and extend the infestation. The Indian meal moth is one of the most common and widespread household pests because the caterpillar stage feeds on nearly every food in kitchen cabinets, as well as on dry pet and bird food.
Eggs of moth pests usually are deposited directly on the food source of the caterpillar stages. Hatching occurs in several days, and caterpillar development is completed in one to three weeks. The number of caterpillar stages ranges from ﬁve to eight, depending on the species and available food. The full—grown caterpillar moves away from its feeding site to form a cocoon and then a pupa. Caterpillars have silk glands that open at their mouths; they use silk to make feeding shelters and to wrap and protect the pupal stage.
Pupae of most species are encased in a silken cocoon; in some species the caterpillar builds a pupal case from the material it is infesting.
Pest status for members of this group is based primarily on the damage each does to stored food, fabric, and other materials. Several species have adapted to indoor habitats and to the food and fabric stored there. The caterpillars ofstored food pests can penetrate the seams and small openings in modern packaging material. The species that attack wool and silk fabric are easily transported to other locations in infested material. Most of the flour and grain pests have been distributed around the world with commercial shipments of food and materials. Moth pests of stored food can be detected with sticky traps that use a pheromone as an attractant. Most traps target a single species, but some use pheromones formulated to attract several closely related species. Pheromone traps can provide information on the species involved, seasonal prevalence, locations infested, and the presence of the adult stage in the population cycle. Pheromone traps release a female sex pheromone or male aggregation pheromone that attracts only males in the vicinity. Males detect low concentrations of this chemical and ﬂy toward the source.