pdf hard copy The authors studied host detection behavior in Alysiinae (Braconidae; Ichneumonoidea) and Eucoilidae (Cynipoidea), the larvae of which are endoparasitoids of fly larvae and investigated whether this behaviour is determined by their descent or can be considered an adaptation to different environments. The authors compared the searching behavior of females of 32 alysiine and 25 eucoilid species from a vareity of microhabitats and from different dipteran hosts by using qualitative behavioral variables. Three main modes of searching were detected: vibrotaxis, ovipositor searching and antennal searching, and the species could be classified according to the role these different modes play in the detection of host larvae. The searching modes are largely dependent upon the taxonomic position ofthe species. In most cases species belonging to one genus show a similar behavior pattern.