S. Nomakuchi et K. Higashi, COMPETITIVE HABITAT UTILIZATION IN THE DAMSELFLY, MNAIS-NAWAI (ZYGOPTERA, CALOPTERYGIDAE) COEXISTING WITH A RELATED SPECIES, MNAIS-PRUINOSA, Researches on population ecology, 38(1), 1996, pp. 41-50
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.