Mortality effects of the parasitoid flesh fly Blaesoxipha japonensis (Diptera: Sarcophagidae) in relation to body size of the adult grasshopper Parapodisma tanbaensis (Orthoptera: Catantopidae)

Body size is a significant factor for organisms because it has a profound effect on almost all of their physiological, life-history, ecological, and evolutionary traits. Sexual size dimorphism (SSD) is one of the sources creating intraspecific variation in body size. In general, female adults are larger than male adults in insects. Whereas much research has examined the significance of male competition and fecundity as causes of SSD in insects, relatively less is known about the effects of parasitoids on host insect size. To investigate the effects of the parasitoid fly Blaesoxipha japonensis Hori on the body size of the adult grasshopper Parapodisma tanbaensis Tominaga et Kanô, we examined the relationship between adult host size and host mortality rate caused by B. japonensis when adult grasshoppers captured in the field were reared in the laboratory. The results showed that females were larger than males and that the host mortality rate caused by B. japonensis was inversely related to host size in females, whereas there was no significant relationship between male size and host mortality rate. These results suggest that the effect of this parasitoid on host body size is one factor favoring the female-biased SSD in this adult grasshopper.