Daily distributions of eclosion and mating activities of Pseudopidorus fasciata Walker (Lepidoptera: Zygaenidae) were recorded under natural and various laboratory conditions. Eclosion of this insect exhibited circadian gating in constant darkness (DD) but not in constant light (LL) at 28°C. Under natural conditions, the majority of adults emerged in midmorning with an eclosion peak around 1000 hours. The eclosion distribution was significantly affected by ambient temperature but not by photoperiod under laboratory conditions. Eclosion was more spread out at 22°C than at higher temperatures, and peak eclosion times were advanced at higher temperatures up to 30°C. Under natural and laboratory diurnal cycles, adults of P. fasciata preferred to mate at dusk, within a few hours before the start of the scotophase. Photoperiod and ambient temperature interacted in regulating the mating distribution in P. fasciata. Mating rhythmicity disappeared under DD and LL, under which the insect either mated arrhythmically (DD) or barely mated (LL). Overall, eclosion rhythm in this insect was predominantly regulated by temperature rather than photoperiod, whereas photoperiod appeared to be more influential than temperature in rhythmic gate of mating patterns.