Unusual cases of product contamination by 'wandering' larvae of the Indian meal moth, Plodia interpunctella (Lepidoptera: Pyralidae)

Upon hatching, the larvae of the Indian meal moth (IMM), Plodia interpunctella, disperse vigorously. Within a few hours, they establish themselves on the crevices of food or enter packaged product through small openings and cracks. When on food the larvae intensively feed in or near a tunnel-like case made of frass and silk they web together. The number of larval instars varies from five to seven, depending on temperature, humidity and available food quality. Most mature larvae leave the food medium and search for a suitable place to spin a cocoon in which they pupate or hibernating (diapause). At the end of larval development, the larvae usually chews a hole in a packaging foil, and leave the medium to pupate outside in corners and cracks and also behind items on walls. Fully grown larvae of the IMM may travel a considerable distance before pupating in a location that is frequently away from the larval food source. It will be proven and illustrated that during this time larvae the IMM may penetrate the packaging material of some household items that were not their food source. Unusual cases of product contamination by 'wandering' larvae will be described. Client claims are thus frequent as only a few larvae in a package with their webbing and frass are very repulsive to homeowners. Impact of product contamination by 'wandering' larvae of the IMM to the firm marketing the products will be discussed.