Why there are so few species of aphids, especially in the tropics.

Abstract

It is possible to account for the distribution and low species diversity of aphids in terms of the constraints imposed by their way of life, namely, the short period for which they can survive without food, their degree of host specificity, and the low efficiency with which they locate host plants. Some 90% of plants are not used as hosts by aphids mostly because these plants are just too rare. -Authors