The Baeini is a species-rich group of tiny scelionid wasps that parasitize the eggs of spiders. Taxonomic research on one genus, Ceratobaeus Ashmead , shows that the 116 Australian species are easily recognized on distinct morphological characters, but only about 25% of them are described . They appear to have very restricted distributions, with almost one-third of species being endemic to the wet forests of north Queensland. Preliminary results from studies on the taxonomy, phylogeny and distribution of Australian baeines are discussed n i relation to their potential in biodiversity studies, given the extensive use of their host group in this way.