Competition for perching sites in the hyaline-winged males of the damselfly Mnais pruinosa costalis Selys that use sneaky mate-securing tactics (Zygoptera: Calopterygidae)

Although hyaline-winged males of M. p. costalis adopt sneak tactics, the competition for occupying a perching site to intercept females entering the territory is severe. To help understand the tactic of the hyaline-winged males, their size, copulation behaviour and reproductive success were examined. The mate-securing tactics of the hyaline-winged males were divided into two. A male which succeeded in occupying a perching site was named a ‘satellite’, while a male which failed was called a ‘wanderer’ . The satellite was usually larger than the wanderer. The satellites were able to copulate with females inside the territory of an orange-winged male. The diurnal rhythm of copulations was similar for each tactic. Copulation duration was longest in wanderers outside a territory. When the duration of oviposition is used as an index of reproductive success of a male, the satellite tactic may be more advantageous than the opportunistic tactic of wanderers. However, from the viewpoint of sperm displacement, the longest copulation duration suggested complete sperm displacement by wanderers. In contrast, the relatively short copulation duration in territorial orange-winged males suggests that not all the sperm of wanderers is removed. Both the occupation of a perching site and the long copulation duration are important for the hyaline-winged males to increase their reproductive success.