COMPETITIVE HABITAT UTILIZATION IN THE DAMSELFLY, MNAIS-NAWAI (ZYGOPTERA, CALOPTERYGIDAE) COEXISTING WITH A RELATED SPECIES, MNAIS-PRUINOSA

Reproductive behaviors related to habitat utilization were studied in males of the damselfly, Mnais nawai, which has two male forms, territo rial orange-winged males (nawai) and non-territorial pale-orange-winge d males (sahoi), at the upper part of a mountain stream where they par tially coexist with a related species, Mnais pruinosa, which also has two male forms, territorial orange-winged males (esakii) and non-terri torial hyaline-winged males (strigata). These two species showed parap atric distribution; the lower part of the stream was occupied by M. na wai, and the upper part by M. pruinosa. In the present study, cross-ma tings occurred between both Mnais species, although normal intraspecif ic matings occurred more frequently than cross-matings. Territorial ma les of both species copulated with conspecific females that entered th eir territory and guarded the ovipositing females, probably to avoid s perm displacement resulting from subsequent copulations. Severe compet ition for oviposition sites by territorial males even occurred between the two species. On the other hand, non-territorial males of both spe cies have alternative mating strategies (including several tactics suc h as sneaking, takeover and interception). The possible benefits from conflict among territorial males of both species is discussed.