DENSITY-DEPENDENT SUPPRESSION OF EXPERIMENTALLY CREATED GYPSY-MOTH, LYMANTRIA-DISPAR (LEPIDOPTERA, LYMANTRIIDAE), POPULATIONS BY NATURAL ENEMIES

Positive density-dependent mortality occurred during the early and mid larval stages and was primarily due to Compsilura concinnata, a polyphagous parasitoid. The oviposition rate of Parasetigena silvestris, an oligophagous parasitoid of gypsy moths, was initially inversely density-dependent but became positively density-dependent during the late larval period. Phobocampe disparis showed an inversely density-dependent response, and predation by small mammals on pupae deployed in the litter was lower in plots with higher numbers of pupae. If gypsy moth population densities fluctuate asynchronously on a spatial scale of a few hectares, the density-dependent responses of C. concinnata and P. silvestris could suppress the populations to a point where small mammal predation would be able to prevent population increase. This may explain the apparent stability of gypsy moth populations on a region-wide basis for the many years between outbreaks. -from Authors