ENDOGENOUS AND EXOGENOUS FACTORS AFFECTING PARASITISM OF GYPSY-MOTH EGG MASSES BY OOENCYRTUS-KUVANAE

Factors affecting the orientation, reproduction, and sex ratio of the egg parasitoid Ooencyrtus kuvanae Howard were examined. Adult females were attracted to airborne volatiles from the egg mass and accessory g land of the primary host, the gypsy moth Lymantria dispar L. Visual cu es also affected host selection. Background colors against which egg m asses were placed affected oviposition preference. In the absence of e gg masses, color variation did not affect wasp behavior. Light is requ ired for parasitism by O. kuvanae. The age and density of both the hos t and parasitoid affected wasp reproduction and sex ratios. Older egg masses issued relatively fewer wasps and higher proportions of males t han did young egg masses. Likewise, wasp reproduction and the proporti on of females declined with wasp age. Larger egg masses produced more wasps and lower proportions of males than did smaller egg masses. The number of offspring per female, and the proportion of female offspring , were inversely related to wasp density. Implications to biological c ontrol of the gypsy moth and parasitoid ecology are discussed.