Host-specificity of folivorous insects in a moist tropical forest

1. To assess the degree of herbivore host-specificity in the moist tropical forest on Barro Colourado Island, Panama, I conducted an extensive series of feeding trials on the common insect herbivores from 10 tree species. 2. The herbivores were offered leaves from both congeneric and confamilial plant species to their known host species, as well as leaves from the most abundant tree species in the forest. 3. The amount of damage caused by these herbivores to young, expanding leaves was also measured on nine of the tree species. 4. Of 46 herbivores species (seven Coleoptera, one Orthoptera, 38 Lepidoptera), 26% were specialized to a single plant species, 22% were limited to feeding on a single genus and 37% were able to feed on several genera within a single family. The remaining 15% were generalists, able to feed from several different plant families. 5. The causes of leaf damage varied extensively across the tree species. On average, specialist herbivores caused 58% of the damage to young leaves, generalists herbivores 8% and fungal pathogens 34%. For four of the tree species, pathogens were the most important cause of leaf damage. 6. In this forest, most chewing herbivores appear to have fairly narrow diets, and these specialists are responsible for most of the insect herbivory.