Experimental invasion of a food container by first-instar larvae of the Indian meal moth, Plodia interpunctella Hubner, through pinholes

Pinholes of several sizes were exposed to Indian meal moths, and larval invasion through the pinholes was examined under the laboratory cage conditions. Hatching larvae could not penetrate 0.020 mm-thick polyethylene film with no pinholes. Pinholes of 0.398 mm or 0.450 mm diameter resulted in as many larvae found in the food container as those of 0.495 mm diameter. Fewer larvae (less than 1/10 of those through pinholes of 0.495 mm diameter) invaded food containers through pinholes of 0.293 mm diameter, and no larvae invaded through 0.173 mm pinholes. Even a single pinhole of 0.495 mm diameter could attract half as many larvae as a container opening of 29.2 mm diameter, demonstrating the importance of a single pinhole. No eggs were deposited through the pinholes even of 0.495 mm diameter, the largest size tested.