THE SIZE AND COMPOSITION OF THE HYMENOPTERAN FAUNA OF COSTA-RICA

An intensive survey of the hymenopteran fauna of Costa Rica provides a n opportunity to explore the size and composition of a species-rich in sect order in a large tropical region. A working estimate of the richn ess of the fauna is 20,000 species. This is consistent with some publi shed estimates of the numbers of species of Hymenoptera worldwide, but at odds with suggestions that all insect species number several tens of millions. Sixty-one families of Hymenoptera have been collected in Costa Rica, and the numbers of species per unit area is more than twic e that of most of the other regions for which data are available. The Costa Rican fauna has higher proportions of egg parasitoids and of eus ocial species, and a lower proportion of primary phytophages than that of the British Isles.