Time and location of larval emergence of the endoparasitoid Cotesia kariyai (Hymenopter : Braconidae) from the lepidopteran host Pseudaletia separata(Lepidoptera : Noctuidae)

The location of a host at the time of larval emergence of a parasitoid is i mportant for successful parasitism and also influences the parasitoid popul ation. Nonparasitized and parasitized hosts stayed in a concealed location (e.g., in soil [vermiculite] or in the leaf fold of the corn plant) during the photophase; whereas during the scotophase, they moved about exposed on the corn leaves. However, only parasitized hosts remained in this exposed l ocation at the time of emergence of the parasitoid larvae. Emergence of the parasitoid larvae always occurred during the photophase. Even when parasit ization was delayed by 6 h, larval emergence occurred only during the photo phase in all eases, suggesting that parasitoid emergence occurred selective ly during the photophase and was not dependent on the duration of developme nt. The time fi om oviposition to emergence was not related to the number o f eggs laid. When a photoperiod of 12:12 (L:D) h was reversed 8 d after par asitization, the parasitoid larvae showed a tendency to emerge according to the new reversed photophase. They appeal ed to emerge in response to the l ight stimulation. We evaluated development by measuring both the size of th e cordal vesicle and the volume of the parasitoid larva. The increase in si ze or volume was slower from 2200 hours on day 9 after parasitization, sugg esting that the lan ae awaited an appropriate chance to emerge from the hos t and were able to regulate the time of emergence. High humidity at the tim e of emergence caused scattered cocoon masses and many naked pupae. Desicca tion after larval emergence promoted high mortality in cocoons.