Earlier studies of the interrelationships between bruchid beetles and their host plants have suggested that the typical pattern tends to be that one bruchid species attacks only a few host species, and that most host species are attacked by only one bruchid species, or at most very few. However, the bruchids attacking Parkia in Amazonian Brazil do not conform to this pattern. The bruchid diversity on Parkia was found to be higher than on any other legume genus yet studied. It is not yet possible to assess whether Parkia is particularly unusual in this regard, or whether such high levels of diversity are typical in Amazonian forests. The number of bruchid taxa attacking any one Parkia species is related to the number of co-occurring closely-related Parkia species. In either taxonomically or geographically isolated host species the bruchid diversity is much reduced.