Behaviour of $ and $ individuals was studied at natural oviposition sites and over dummies of black plastic foil, black cotton and glass splinters on various backgrounds. Choice experiments revealed that both sexes are attracted chiefly by reflecting surfaces (on dark background). Male individuals responded by patrol flights including hovering, repeated surface-touching and site defence. Females exhibited inspection flights and (rarely) oviposition movements. The frequency of arrivals and the duration of stay over dummies in comparison with natural oviposition sites were quantitatively analysed.