Structure of two macrolepidopteran assemblages on Salix nigra (Marsh) and Acer negundo L.: abundance, diversity, richness, and persistence of scarce species

1. Most insect species occur at low abundance but a greater research effort has been devoted to so-called outbreak species and little research is avai lable on scarce (low abundance) species that are typical of most insect spe cies. 2. Larval free-feeding macrolepidoptera of two riparian trees Salix nigra ( Marsh) (black willow) and Acer negundo L. (box elder) were sampled and sort ed by species and abundance. 3. Data collected established that the majority of species in the assemblag es in each tree species occurred at low abundance in each of the 5 years wh en larvae were sampled. 4. Species in the Noctuidae and Geometridae dominated both assemblages. 5. On both trees, assemblages were dominated numerically by relatively few species, a pattern that has been observed for insect assemblages on plants in managed and unmanaged habitats.