Evaluation of a novel emergence trap to study Culex mosquitoes in urban catch basins

Stormwater catch basins in urban areas provide important larval habitat for Culex mosquitoes. In this study we quantified adult Culex emergence using a newly designed emergence trap deployed in catch basins in suburban Chicago, IL. Traps were deployed from late June to mid-October, 2009-10, in 19 catch basins for a total of 461 trap-days. Based on laboratory trials, the percentage of adults emerging under the trap and reaching the collection cup ranged from 37.7 +/- 6.5% for closed-cup and 50.5 +/- 3.8% for open-cup configurations. In 2009, catch basins containing immature mosquitoes produced an estimated 58.9 +/- 30.8 female and 86.2 +/- 36.4 male Culex spp. per day. Most (84.4%) were Culex pipiens and the remainder were Cx. restuans. The trap was also effective in documenting reductions in adult emergence following intense precipitation events that caused "flushing" of larvae and pupae. In general, the new emergence trap was effective for studying Culex production in catch basins and should be broadly useful in studies of container-breeding mosquitoes.