Adult emergence rhythm of the egg-parasitoid Telenomus busseolae

The adult emergence rhythm of Telenomus busseolae, an egg parasitoid of Ses amia nonagrioides, was examined when parasitoids were exposed to different light-dark regimes. Most of the adult parasitoids emerged throughout the wh ole period of the photoperiodic cycle. Peak male emergence occurred 2-5 hou rs earlier than that of females. Adult emergence was asynchronous in contin uous darkness or light. However, regimes of alternative light and dark phas es such as L4:D20, L8:D16, L12:D12, L16:D8 and L20:D4 h generated a populat ion rhythm with a period length of 24 hours. The peak of the emergence acti vity moves from the scotophase to the middle of the photophase with an incr ease of the photophase from 4 to 20 h. Rhythmical activity of adults was sy nchronised within 2 cycles when immature stages of parasitoid grow under co ntinuous light conditions (LL) and then transferred to L12:D12. Moreover, e mergence rhythm persisted and continued in a free-run with a period length of less than 24 hours by transferring a rhythmic culture from L12:D12 h to LL or RR (continuous red light) conditions, indicating the existence of a c ircadian rhythm. The ecological implications of the expression rhythm relat e to better survival of the parasitoids.