none The influence of parasitoid female Biosteres longicaudatus Ashmead (Hymenoptera: Braconidae) densities on their mortality, oviposition, and superparasitization (> 1 egg per host) and on progeny sex ratio was evaluated. Three ovipositional tests were conducted. Methodology is described. Aggression, mortality, superparasitization, and male progeny increased with parasitoid density. Mean oviposition was inversely related to parasitoid density. Large females (> 3.5 mm) laid more eggs than small ones (< 3.5 mm) when only the preferred fruit fly larvae were provided. However, when house fly larvae were also available, small females oviposited primarily in these hosts to decrease competition.