Swarming behaviour of the mosquito Culex pipiens quinquefasciatus: a quantitative analysis

ABSTRACT. Analysis of video recordings of Culex pipiens quinquefasciatus Say swarms showed that the overall swarming patterns of males and virgin females are similar, even though the short-term characteristics of their flight, such as speed and turning angle, differ. This suggests they have the same response to the visual cue of the swarm 'marker'. The swarming pattern of an individual consists of elliptical loops which, in the short-term, define an area smaller than the swarm as a whole. The foci of these ellipses drift gradually with respect to the marker; individuals do not seem to have preferred positions within the swarm, but drift at random. Male mosquitoes identify and locate females by the sound of their wing-beats. Diffuse sound at the wing-beat frequency of female C.p. quinquefasciatus (500–600 Hz) caused males within the swarm to slow down significantly. Their turning behaviour remained unchanged, so the ellipses decreased in size. The swarm as a whole collapsed into a smaller volume, centred over the marker. Apparently, the response of males to sound consists of at least two parts: initially they alter their flight speed, and then alter their turning behaviour once they have located the source of the sound.