Ecological studies of Ischnura elegans (Vander Linden) (Zygoptera: Coenagrionidae). II. Survivorship, local movements and dispersal

Imaginal populations of I. elegans were studied by means of capture-recapture methods in Cheshire and Pembrokeshire, U.K., from 1965 to 1970. Although the survival rates did not alter with time, the populations had characteristic survival rates which differed from each other. This was probably due to differential predation by birds. Survival was shown to be heavily age dependent, the heaviest losses occurring at the teneral stage. Maximum survival was 42 days for males and 50 days for females. No evidence was obtained to indicate a general movement away from water by teneral insects: many individuals stayed at the water’s edge during the maturation period. The maturation period may be as short as three days (males) or four days (females), although it is probably usually a little longer. Many individuals do not move more than 100 metres from their emergence site. A few individuals are wanderers over relatively great distances and are presumably important as founders of new colonies. In many respects (great general adaptability, activity in cool and dull weather, rapid maturation which is usually at water, persistence of females at water, and a very long copulation time) I. elegans does not conform to what seem more general zygopteran characteristics.