Differences in male and female activity patterns in the dragonfly Sympetrum danae (Sulzer) and their relation to mate-finding (Anisoptera: Libellulidae)

Flight activity patterns were studied under semi-natural conditions in a large outdoor field cage in which individuals were found to show normal behaviour. Sexual differences in usage of time and space and the influence of temperature were studied. Before solar noon males were mainly active away from the pond, where they searched for females if temperature was high enough. Most pair-formation was seen during this period. Around noon and in the early afternoon, acticity shifted towards the pond, where some more pairs were formed. Throughout the afternoon male activity decreased, and shorter, localized flights became relatively more important. Male maximal flight activity coincided with solar noon and peak reproductive activity. Females remained almost inactive throughout the morning. However, their activity increased rapidly from noon onwards and largely exceeded male activity in the late afternoon. Female activity at the pond was always low compared to that in the surroundings. Females preferred more overgrown parts of the cage than did males, and selected higher perches. Body-surface temperature had a positive exponential effect on flight activity within the interval 20°-40° C, the effect being stronger in males than in females. Higher temperature also had a positive effect on the selected perch height. The results demonstrate that observations made only at the waterside can give a misleading impression of total activity. The revealed sexual differences in activity patterns are discussed in relation to mate-finding strategies in both sexes.