Temperature adaptation in Chrysomya megacephala and Chrysomya pinguis, two blow fly species of forensic significance

Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) is a common and forensically important blow fly species in the Oriental region. However, in the higher mountain regions and on winter days, its habitats are occupied by a closely related species, Chrysomya pinguis (Walker). The resources that the two species employ to survive are very similar and competition between the species may be one of the factors that trigger differentiation of their behaviors. We conducted experiments to examine how these two closely related species may have adapted to different temperature regimes to avoid competition. Several adult and immature parameters were assessed, such as fecundity, locomotor ability, hatching ratio, larval survivorship, and eclosion ratio. Results indicate that species show specific diapause at high temperature (38 degrees C), larval survivorship of Ch. megacephala was significantly better than that of Ch. pinguis. Conversely, at low temperature (15 degrees C), adult locomotor ability was better for Ch. pinguis than for Ch. megacephala. The results indicate that the two species may have evolved different temperature adaptation strategies to avoid competition. In mixed-species larval rearing experiments, competition between Ch. pinguis and Ch. megacephala was observed: at higher temperature (30 degrees C), the immature performance index of Ch. megacephala was significantly increased when compared to that in single-species culture, whereas the index of Ch. pinguis was decreased. These data are consistent with the idea that tolerance for higher temperature conditions would allow larvae of Ch. megacephala to gain a competitive advantage over Ch. pinguis in certain habitats. These results may help to explain their current distribution in the environment and provide more biological information on these forensically important species.