Female moths [Lymantria dispar (L.)] that had begun to deposit unfertilized eggs (spewing females) did attract males and were mated. However, only females that had spewed fewer than 10 eggs before mating were likely to deposit fertile eggs after mating. Males in a natural infestation did not discriminate between mated, virgin, spewing and nonspewing females. Both sexes of the gypsy moth were capable of mating several times in 24 h. About 1/3 of the males in a dense population mated with previously mated females. In the microencapsulated, disparlure-treated plots, only 1- to 4-day-old females were mated. In untreated plots, 1- to 8-day-old females were mated. Furthermore, fewer females tethered in the litter in the treated plots were mated than those females tethered in the litter in control plots. The disparlure treatment reduced the incidence of mating. In treated plots, more females tethered on the tree at 2 m were mated than females tethered in the litter. Videotaped activity of males in a dense population revealed that males orient to vertical silhouettes initially, and not to specific pheromone sources.