Studies were conducted to determine the effects of the different conditioning of exotic ectoparasitoid Catolaccus grandis (Burks) females on their oviposition activity and mortality of the host [the boll weevil, Anthonomus grandis grandis (Boheman)]. Eggs are laid and a feeding tube is formed only by conditioned (post-preovipositional period and exposed to the host for a 2-d period) or unconditioned (post-preovipositional period but no exposure to host) parasitoid females. Feeding-tube formation without oviposition occurs when newly emerged (ca. 10 h post-emergence) females discover their first host larvae. Catolaccus grandis conditioned females are oviposited more actively in time of attacked boll weevil larvae than unconditioned females (66.7% versus 29.2%). Laboratory studies showed that reproductive mature C. grandis females induced significantly higher levels of mortality on boll weevil larvae than newly emerged females. The highest survival of parasitoids to the pupal stage was observed in host larvae where the C. grandis females oviposited (60.0%). Venom extracts from newly emerged females were significantly less effective paralyzing and killing host larvae than those from mature conditioned or unconditioned females. This may indicate that the venom activity on newly emerged females is not completely developed. The venom extracts of conditioned and unconditioned mature females were equally effective inducing paralysis and death on boll weevil larvae. The injection of venom to paralyze the host and the oviposition of C. grandis females are, in many cases, independent processes.