Observations on male swarms of Psorophora columbiae in Texas ricelands.

The evening swarming behavior of newly emerged male Psorophora columbiae was studied in eastern Texas ricelands. Near infrared-sensitive video equipment was used to record swarming as it occurred in the field during each night of observation. Males of Ps. columbiae form either funnel-like or curtain-like marker swarms over a variety of objects in a riceland habitat. The sequence of events leading to swarm formation is described. Swarming males fly into the wind and follow a figure-8 pattern of flight. This flight pattern is modified by other insects flying through or near the swarm. Sudden changes in wind velocity or direction also modify the position and shape of the swarm relative to the marker over which it has formed.