Wat is de functie van demonstreren van het achter lichtje door mannetjes van beekjuffers (Calopteryx)?

Suggested functions of the “tail-tip” or “water” display in males of the European species of Calopteryx are discussed, using literature data on various species and own observations on C. haemorrhoidalis. Courting males show the light-coloured ventral side of the last three abdominal segments (the “rear light”) in a conspicuous way by curling up the tip of the abdomen and spreading the dark-coloured wings as a contrasting background while hovering just above or floating on the water surface. This display is shown in the centre of the territory, both during initial courtship and after copulation. As a signal to the female, the display might indicate both the ownership and location of an oviposition site as well as its quality (e.g. current speed of the water if floating is included). Moreover, it might give some indication of the quality of the male. In the present paper, it is argued that indication of the exact oviposition site appears to be the most important among these possible functions.