Dispersal of Female Culex Tarsalis into a Larvicided Area *

Abstract

Summary Trapped mosquitoes, mostly Culex tarsalis, were dusted with four different fluorescent pigments and released 1.0 to 1.4 miles beyond the four corners of an area in which larvicidal control methods had failed to secure the desired reduction of the adult population. Marked specimens of each color were recovered in the center of the area at distances of 4.0 to 5.6 miles between 10 and 23 days after the first release. The dispersal was slow and apparently the result of appetential flights in random directions. The widest dispersal appeared to spread radially at the rate of about one mile every three days, but the greatest density of marked mosquitoes remained near the release points. In a second test, reared as well as trapped specimens of C. tarsalis were marked and released beyond opposite corners of the treated area. Excepting one problematic recovery, there was no evidence that the young, reared specimens dispersed in a migratory flight; moreover, movement appeared to be delayed by immaturity. The maximum distance at which any recovery was obtained was 9.6 miles. There was no apparent influence of prevailing winds.