The number of insect species on a small oceanic island: two solutions to a Fermi problem

Where the number of species of a particular taxon is not sufficiently known even to allow an estimate by extrapolation, the question becomes
a Fermi problem. This approach is used to estimate the total species richness of insects on the very small Dutch island of Saba in the Caribbean. Two solutions each lead to estimates of about 8400 or 8500 species. It is suggested that (i) this estimate is probably not very far from the true total, and (ii) reaching a more confident estimate would be a worthwhile project for the Dutch entomological community.