Calyx and Venom Fluids of Apanteles kariyai (Hymenoptera: Braconidae) as Factors that Prolong Larval Period of the Host, Pseudaletia separata (Lepidoptera: Noctuidae)

Abstract

An examination was made of inhibitory effects of calyx and venom fluids of Apanteles kariyai Watanabe on pupation of the host, Pseudaletia separata Walker. The larval stage of the host was prolonged an average of 3 d when calyx and venom fluids of the parasitoid were simultaneously injected into the host. A single injection of either fluid alone had less effect. When calyx and venom fluids were injected into day-0 fifth instars, normal larval/larval ecdysis occurred, and only larval/pupal ecdysis was delayed. Calyx fluid kept at −20°C for 1 d failed to have any effect on prolongation. Characteristics of virus particles in calyx fluid seem to be unstable. Venom fluid was effective even at a fairly dilute concentration; calyx fluid was ineffective at 1/8 dilution. When calyx and venom fluids were injected at the same time together with crude prothoracicotropic hormone into an isolated abdomen implanted with the prothoracic glands from the day-2 stage of the last (sixth) instar, the crude hormone ceased to have any stimulatory effects. Prothoracic gland activation is apparently disturbed and suppressed by calyx and venom fluids.