Fast, temperature-controlled colour changes in Chlorocypha straeleni Fraser (Zygoptera: Chlorocyphidae)

The dorsal surface of the abdomen of male C. straeleni is bright red at temperatures above 30-35°C. but it turns grey-black in 25-40 min when cooled to 25°C. On return to > 35°C the bright red colour may return in < 10 min. The abdomens of territorially active males observed al a forest stream in Uganda were always found to be bright red. Similarly the abdomen of Platycypha caligata turns from blue to grey-blue when cooled. In both species darkening is due to the distal migration of black pigment granules within the epithelial cells. At high temperatures the granules become clumped proximally near the basement membrane. Darkened males may be less readily delected by predators or rival males.