Males of Platycnemis latipes (Platycnemididae, Odonata) have enlarged tibiae (fans) and patrol using a special longitudinal zig-zag flight. By means of focal observations and experimental manipulations of the colour of abdomen and fans of mature males, we suggest that the zig-zag flight is used to avoid unnecessary harassment from other males and has not the function to attract females. The fans of P. latipes are mainly used as a tool to threaten rivals, but their effectiveness seems limited. Both abdomen and fans of a mature male can reflect UV light strongly.