Pheromone-Mediated Diel Activity Rhythms of Male Asian Gypsy Moths (Lepidoptera: Lymantriidae) in Relation to Female Eclosion and Temperature

Abstract

Male Asian gypsy moths, Lymantria dispar (L.), were attracted to synthetic pheromone ( cis -7 R ,8 S -epoxy-2-methyloctadecane) in the Russian Far East, Central Siberia, and Germany, where this strain has recently been detected. A bimodal pattern of attraction was evident at all 3 sites. One peak of attraction was in early to midafternoon, with a 2nd, usually smaller peak, following sunset. Temperature modulated attraction: warm daytime temperatures increased catch, whereas low nighttime temperatures generally suppressed or eliminated attraction. However, the surge of male attraction to pheromone in the hour after sunset seemed unaffected by falling temperatures. As average temperatures at the 3 sites decreased, the daytime peak of male activity progressively shifted to later in the afternoon. Female eclosion in Germany also followed a bimodal pattern, with a major midmorning to midday peak of emergence and a 2nd, smaller peak, in the afternoon. The timing of male attraction allowed coordination of the ranging flight of the male with the availability of emerging and pheromone-emitting females. The congruence in daily activity patterns suggest that the timing of mating would not be a barrier to the hybridization of the Asian, European, and North American strains of this lymantriid in new areas of sympatry.