RESUMO
Spatial distribution of mosquitoes around a bovine host was studied in November 1997 in northern Thailand (17 degrees 38'N. 99 degrees 23'E). Forty bamboo stakes were arranged 1 m apart, in 4 rays of 10, around a cow tethered in an open field. All mosquitoes found resting on the stakes were collected by aspiration between 7:00 p.m. and 11:00 p.m., sexed, and identified to species; and feeding status was categorized as fed or unfed. Collections were repeated over 8 nights, with and without the host cow. A total of 1,566 mosquitoes from 25 species (5 genera) was collected. Anopheles aconitus was the most abundant species (643 individuals), followed by An. peditaeniatus. Culex vishnui, and Cx. pseudovishnui. We found that the number of mosquitoes collected from the stakes was related to the presence of the cow host: the number of mosquitoes collected was unrelated to the compass point location of the bamboo stakes, with the exception of Mansonia uniformis; unfed mosquitoes preferred bamboo-stake resting sites that were closer to the host; the daily fed to unfed ratio of the dominant species was negatively correlated with the daily total number of mosquitoes collected; and fed and unfed mosquitoes clustered in interspecific heterogeneous groups around the host cow. Cluster analysis separated the species into 2 groups. The 1st consisted of 5 species with higher proportions of fed mosquitoes, whereas the 2nd, represented by 7 species, aggregated around the host within a distance of 1-4 m with lower proportions of fed mosquitoes. The interspecific variation in the distribution of unfed females was presumed to be due to a lack or feeding success. We discuss the significance of prebiting resting. In cases in which large numbers of mosquitoes are present, prebiting resting can be adaptive to avoid host defensive behavior triggered by attacking mosquitoes.