AbstractRastrococcus invadens Williams, a serious pest of fruit crops in West Africa was studied under controlled conditions. The different stages of the mealybug are described and data given on development times, adult lifespan, fecundity, sex ratio and mortality rates. Similar data are also given for a primary parasitoid, Gyranusoidea tebygi Noyes. The parasitoid completed almost two generations for each one of the mealybug and had a female-biased sex ratio compared with a male-biased one for R. invadens. The parasitoid did not parasitize other species of mealybugs offered. G. tebygi was considered a suitable candidate for a biological control programme and was introduced into Togo in October 1987.