Indian Meal Moth, Vol. 8, No. 3
Plodia interpunctella
Order: Lepidoptera
Family: Pyralidae
“This worm was in my milk! I got a glass from the cupboard and set it on the countertop, got the milk from the fridge, broke the seal to open the jug, poured the milk, and put the jug back in the fridge. As I was about to take my first sip, I saw this worm squirming about on the surface! The glass was upside down in the cupboard when I got it, and I know the worm was not in the glass. It could only have come from the milk jug! How can a live caterpillar come to be in a new jug of milk?”
It took a bit of head scratching to get started on this one, but with any insect problem of this type, the first step is to identify the insect involved. This caterpillar did not have a lot of traits that could be used for identification, but the ones it did have helped to identify it as an Indian meal moth caterpillar, and this suggested a possible explanation.
Indian meal moths are common household insect pests. The moths are a bit over a half-inch long and hold their wings parallel to their body when at rest. The basal part of the wings, nearest the head, are cream colored, while the outer half are a distinct coppery red. This makes these moths easy to identify, and if you see them flying about your house, it is time to start searching through the pantry for infested food products.
The caterpillars feed on a wide range of dry, grain-based food products, as well as things like nuts and dried fruits. Things like boxes of cereal or pancake mix, pasta and other dry processed foods, shelled nuts, dried apricots, and other dried fruits, as well as things like bird seed and dry pet food. Heavy infestations are relatively easy to spot, as there will usually be a lot of webbing and perhaps a bad odor. Lighter infestations are harder to detect, but if you have an infestation of Indian meal moths in the house, any susceptible products that are not stored in insect-proof containers are likely to be infested. Mature caterpillars sometimes crawl some distance away from the place where they developed before pupating in some type of crevice or corner. Often larvae will crawl upward and pupate on the undersides of shelves where they meet the wall, or at the corner of the wall and ceiling.
I called the client back and suggested she look through the kitchen cabinets for Indian meal moth infestations. A couple hours later she reported that they were in the Cheerios and the pancake mix. Apparently, a wandering larva happened to fall into the glass of milk during the few seconds when she was returning the jug of milk to the refrigerator.
Control: See the “Stored Food Pests” section of Extension Publication, 2443, Control Household Insect Pests, for more information on how to detect and control Indian meal moths and other stored food insects.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.
Mississippi State University is an equal opportunity institution.
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