Quantitative and qualitative variation in male pheromones of Phragmatobia fuliginosa and Pyrrharctia isabella (Lepidoptera: Arctiidae)

The dihydropyrrolizine pheromones, hydroxydanaidal and danaidal, were identified from the scent organs of male Phragmatobia fuliginosa (L.) and Pyrrharctia isabella (J.E. Smith). Qualitative and quantitative GLC analyses were conducted on ca. 80 field-collected males of each species. The total pheromone titer was distributed bimodally in each species with most males having either a small amount (< 10 ng) on pheromone or a large amount (1-10 mu g in Pyrrharctia and 0.3-3 mu g in Phragmatobia). Pyrrharctia males in the 1- to 10 mu g range had a predominance of hydroxydanaidal, with little if any danaidal. Most Phragmatobia males in the 0.3- to 3- mu g range had danaidal with little if any hydroxydanaidal. These compounds elicited a courtship response in sexually receptive females of both species.