Brachypterism and Seasonal Adaptation in Orgyia thyellina BUTLER (Lepidoptera, Lymantriidae)

概要

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The vapourer Orgyia thyellina shows conspicuous seasonal as well as sexual dimorphism in wing development. The females emerging in summer have normal wings, but those in autumn atrophied wings. This was found to be controlled by the photoperiod during the larval stage. At 20℃ the brachypterous form was prevalent in LD 12 : 12 hr to 14 : 10 hr, and its frequency decreased with either longer or shorter photoperiods. A sharp shift in wing form occurred between LD 15 : 9 hr and 16 : 8 hr. This response was closely associated with the incidence of egg diapause. Brachypters usually laid diapause eggs, while macropters nondiapause eggs. The diapause eggs were larger in size and darker in marking than the nondiapause ones. A further effect of photoperiod was revealed by the pupal melanism. The pupae tended to be darker in photoperiods producing brachypters. The seasonal brachypterism seems to have been evolved in conjunction with the selection of cocooning sites by the mature larvae, and its adaptive significance probably lies in securing oviposition sites (cocoons) favourable for survival of the overwintering eggs.
日本昆虫学会の論文
1977-03-25