Some Wing-Padded Larvae of Pseudoregma bambucicola (Homoptera: Aphididae: Hormaphidinae) Overwinter and Develop into Virginoparae

Abstract

Pseudoregma bambucicola, an Asiatic eusocial aphid, shows a typical life cycle of host-alternating aphids in Taiwan. It sexually reproduces on primary host trees and parthenogenetically produces offspring including sterile soldiers on secondary hosts. However, in southern Japan where this aphid species is thought to have been artificially introduced with secondary host plants and where there are no candidates for primary host plants, the apterous virginoparae propagate parthenogenetically throughout the year on the secondary host, still producing numerous alate sexuparae in autumn. In the present study, I collected 18 wing-padded aphids in winter and the following spring and, by rearing them, ascertained that these abnormal individuals grew not to sexuparae but to adult virginoparae which produce "normal" first-instar larvae and soldiers on the secondary host. This suggests that natural selection favors some wing-padded aphids to abandon flight probably due to the high mortality of alate immigrants, supporting the idea that the alates may play no significant role but may be produced by phylogenic inertia in Japan.