Female sexual receptivity and male copula guarding during prolonged copulations in the damselfly Ischnura senegalensis (Odonata : Coenagrionidae)

Laboratory experiments were conducted to clarify the relationship between f emale sexual receptivity and male copula guarding in I. senegalensis, a spe cies that copulates for several hours. In insectaries, most copulations wer e initiated early in the morning, and terminated relatively synchronously b etween 11 00 and 13 00. Females refused males with wing-flutter display and oviposited alone in the afternoon regardless of copulation events of that morning. Females could sexually receive males only in the morning. Males co pulated for several hours until 12 00 after which females could oviposit. T o determine whether copulations that last for hours function as male copula guarding or only of sperm displacement, emerged males were kept at various densities and permitted to copulate with virgin and mated females in insec taries. Both with virgin and mated females, "social" (not solitary; 2-4 mal es / insectary) males initiated copulations early in the morning and always terminated at around 12 00. However, both with virgin and mated females, s olitary (one male / insectary) males terminated copulations in the morning. In both cases, duration of copulations did not significantly differ for vi rgin females and mated females. Therefore, long (several hour) copulation i s more likely to function as male copula guarding than as sperm displacemen t, and duration of copulations is predicted to be shortened when male densi ty is very low.