Dispersal of Plecia Nearctica (Diptera: Bibionidae)

Randy Thornhill


The dispersal and flight activities of Plecia nearctica Hardy were studied by 2 mark-recapture techniques. First flies were collected with a D-Vac and agitated in a 1-gal jar containing Day-Glo fluorescent dust. Then the flies were released in an area containing sticky traps placed in a circular pattern around the release point at distances of 100, 200, 300, 400, and 500 ft. The second marking technique involved dusting resting flies in a grassy area with Day-Glo pigment in the late afternoon after the flies had settled for the evening. With the release technique, more flies were recaptured at 100 ft than at any distance greater than 100 ft from the release point. Beyond 100 ft and up to 500 ft similar numbers of marked flies per trap were recollected. With the dusting technique the number of marked flies recaptured decreased at increasing distances from the center of the dusted area. No significant differences were found in the distances moved by single males and females or copulating pairs with either marking technique. There were also no differences in the directions moved by the 3 categories of flies after either marking technique. Dusting flies on the vegetation is the more desirable marking technique because no handling of the flies is necessary.

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