Population Regulation of a Leaf-Mining Insect, Cameraria Sp. Nov., at Increased Field Densities

We experimentally induced increased field densities of a leaf—mining insect, Cameraria sp. nov. (Lepidoptera: Gracillaridae), but caging a Quercus nigra (Fagaceae) tree to compare insect mortality and survivorship with that on a control tree. Although densities of the leaf miner were significantly higher on the caged tree, larval survivorship did not decrease as expected if intraspecific competition is density dependent. Rather, survivorship increase. We attribute the significantly higher larval emergence rates to exclusion of most parasites and predators from the cage tree. We contend that natural enemies of leaf miners, particularly hymenopteran parasites, are instrumental in maintaining leaf—mining populations far below levels at which intraspecific competition would occur.