Morphology and development of the short wing in the seasonal dimorphism of the tussock moth, Orgyia thyellina (Lepidoptera: Lymantriidae): comparison with the long wing

Abstract

In the tussock moth, Orgyia thyellina Butler, the female adults produced from the larvae reared under a short-day (SD) photoperiod are short-winged, while those under a long-day (LD) photoperiod are long-winged as most lepidopterans are. To characterize morphology and development of the short wing of the SD adult, we examined the adult and pupal wings of the SD and LD females by optical and scanning electron microscopy. The examination of the adult wings showed that the wings of the SD females are much thicker and rougher than those of the LD females. The wing veins of the former look wavy, while those of the latter straight. The wing scale morphology of the former was similar to that of the latter, while the scale density of the former was much higher than that of the latter. The examination of the fully developed pupal wings showed that the wings of the SD pupae are morphologically similar to those of the LD pupae, and also to the short wings of the SD adults. The results indicate that the short wing of the SD adult is developed almost without spreading the fully developed pupal wing, unlike the previously reported processes of the short wing development involving massive cell death.