SWARMING BEHAVIOUR OF THE LESSER HOUSE FLY, FANNIA CANICULARIS, IN BRISBANE

Abstract

Studies of the lesser house fly, Fannia canicularis, in Brisbane, Queensland showed that males swarmed at closed in sites, such as under and inside houses. Flies preferred the centre of an area, though variations in light intensity and the presence of objects in the swarming area modified this behaviour. When temperatures remained above 15°C, swarming occurred from about sunrise to sunset, though on days with a maximum above 25 °C, few swarmed near midday. Males flew for long periods in semi‐rectangular circuits, though at high fly populations such circuits were often not completed as flies constantly chased each other. Resting males also chased flies or objects that moved rapidly within two metres of them; slow moving objects were ignored. Although F. canicularis forms swarms like smaller Diptera, this chasing of other males is characteristic of the waiting station and territorial defense of larger species. On coming to land, males preferentially faced and alighted head upwards; most then turned to rest head downwards, thus accounting for the head downwards posture of resting males noted here and elsewhere.