Invasion of the cup-packaged instant noodles by the Indian meal moth, Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae), and development of the larvae on the instant noodles.

This study examined the mechanisms by which the Indian meal moth, Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae), invaded instant noodles packaged in a heat-shrunk sealed foam polystyrene cup, and the development of the larvae feeding on the instant noodles. The last-instar larvae tended to invade the space between the shrunk film and the cup. We observed numerous enlarged holes bitten by larvae on the air vent holes and holes on the back lining (the seal between films) of the PP (polypropylene) film covering the side and the bottom of the cup. On the lid flange, it was confirmed that larvae bored through the foam polystyrene as well as the PP film of the lid flange to enter the inside of the cup, where they fed on the instant noodles. When the larvae were reared on the instant noodles from first instar, the average larval developmental period at 30 degrees C was 33.1 days (males) and 34.3 days (females), being significantly longer than when fed on the rice bran. The percentage of adult emergence was 30.0. From the viewpoint of prevention of insect contamination, we concluded there was room for improvement of the heat-shrunk packaging and the cup surface of the instant noodle product.