The West Indian region is one of Conservation International's most critical biodiversity hotspots. Because of massive extinctions among the vertebrate fauna, insects are of even more than usual interest in understanding the biodiversity of these islands. The species/area relationship can be used to predict the richness of unsampled islands, providing enough islands are well inventoried. We use data from the genus Phyllophaga Harris to construct a predictive tool for understanding this group. Because of very high numbers of single-island or bank endemics among members of this genus, the species/area relationship may help clarify the impact of under sampling on our understanding of regional biodiversity.