A male Libellula depressa was observed to mistake a dark-green passenger coach for a water body thus establishing his territory over the surface of the vehicle and using the radio antenna as perch. A videopolarimetric analysis of the car body showed that the light reflected from the bonnet was highly and horizontally polarized with rather…
The European Platycnemis acutipennis and P. latipes and the African Mesocnemis singularis aggregate during oviposition. Choice experiments show that, in all three species, groups develop because tandems preferentially land where conspecifics already show oviposition behaviour. Just a single motionless male in the typical vertical position of a tandem male stimulates aggregation and oviposition behaviour in…