Parasitism of Parapodisma grasshopper species by the flesh fly, Blaesoxipha japonensis (Hori) (Diptera: Sarcophagidae)

Abstract

I examined parasitism of two grasshopper species, Parapodisma tanbaensis and P. subastris, by the flesh fly, Blaesoxipha japonensis, the genus of which includes important parasitoids of grasshoppers and locusts. I collected adult grasshoppers in the northern suburbs of Kyoto from late July to late October 2001 and reared them in the laboratory to investigate parasitism. The parasitism rates were greater for P. tanbaensis than for P. subastris, except for those in Kurama, where no parasitism was observed. The puparial weight decreased as the larval density within the host increased. This tendency was significant only for female hosts, since more puparia often egressed from female hosts than from male hosts. Male puparia were generally heavier than female puparia; this was more evident in female hosts with fewer than three fly larvae. In contrast, puparial weight did not differ by sex when puparia egressed from male hosts. These tendencies were also confirmed in the laboratory experiments. These results suggest that female hosts provide potentially greater resources for fly larvae than male hosts, and that male larvae develop considerably larger at low larval density.