Females vs Males
Lacking a digestive system, adult Lymantria dispar moths essentially the sex organs of the caterpillars. They only live about a week. But what a week (more on that below)! The specific epithet, dispar, is related to the word disparate, for separate or different, and refers to the sexual dimorphism between males and females. Females are about 33% larger than males, but it’s probably easier to differentiate the sexes by three key features: (1) color, (2) behavior, and (3) antennae.
The females have bright white wings with small black speckles, and their shiny brown body is often visible near the head. Though they have large wings, the females are entirely flightless, remaining in one place on the trunk (often near clusters of pupal casings) waiting for the males to arrive. To assist the bumbling quests of males, females release a pheromone, disparlure (source), that attracts males to their white beacon of a body. Female antennae are thin, black, and poorly developed.
Males are brown, with the same shiny brown spot just behind the head. Contrasting with the sedentary females, males fly frantically near the base of trees trying to pinpoint the source of pheromones. Owls have offset ears to pinpoint the sound of voles under the snow (video), and this type of flight helps triangulate the source of the pheromone. They’re assisted in the hunt by well developed, feathery antennae.