[Clusters of aberrant scales after X-radiation of the wing anlagen in female diapause and nondiapause caterpillars of Plodia (Lepidoptera)].

In diapausing last-instar caterpillars (rearing temperature 20° C) of the Indian Meal MothPlodia interpunctella H., all nuclei of the posterior wing anlagen (about 2700 cells each) are in the prophase stage. In non-diapausing larvae (30° C), on the other hand, a considerable variety of mitotic stages can be observed.When female caterpillars are irradiated (4000 R) in the 2700 cell stage, clusters of aberrant scales are found on the wing of the imago. The appearence of scales may vary within one cluster. 10 different "somatic mutants" are distinguishable on the upper side of the posterior wing. Their differences in shape, color, and pattern of the ribs are described.The two most frequent "somatic mutants", PS 1 (808 "mutations" in all) and PS 3 (184 "mutations") were evaluated quantitatively: In irradiated wings, the ratio of PS 1 clusters of diapause vs. non-diapause wings (100∶57) is similar to the corresponding ratio of prophase stages (100∶56). For PS 3, the cluster ratio is 100∶87. In unirradiated wings, clusters of both mutants are rare. There are no differences of the frequencies of solitary mutant scales between irradiated and unirradiated wings.The question is discussed, whether the mutations are induced hi a non-diapausing wing anlage during the prophase stages only.