Effects of different pyrethroids on landing behavior of female Aedes aegypti, Anopheles quadrimaculatus, and Culex quinquefasciatus mosquitoes (Diptera: Culicidae).

Mosquitoes from three genera, Aedes aegypti L., Anopheles quadrimaculatus Say, and Culex quinquefasciatus Say, were tested for facultative landing and resting behavior on pyrethroid-treated surfaces paired with adjacent untreated surfaces. The three pyrethroids tested were bifenthrin, deltamethrin, and lambda-cyhalothrin. Landing and resting behavior was video recorded and quantified using Observer XT software. Untreated control treatments were tested to show behavior in the absence of insecticides. In controls, the three species had different activity levels, with An. quadrimaculatus being the most active and Cx. quinquefasciatus being the least active. The three species had unique responses to different compounds tested. Landing frequency on adjacent untreated and treated filter papers did not differ for any compound or species at any time during the experiment. However, landing frequencies did differ between treatments and over time. Differences between treated and untreated sides were largely caused by changes in the length of time mosquitoes rested on each side. An. quadrimaculatus had a unique response to the presence of deltamethrin compared with the other species or compounds in which it spent an increased amount of time in contact with both treated and adjacent untreated surfaces. Cx. quinquefasciatus avoided all three compounds by the end of the experiment and rested longer on untreated sides. In most cases, modification of landing and resting behaviors occurred only after mosquitoes had the opportunity to come into contact and acquire a dose of pyrethroid. Bifenthrin had the fastest TK50 for all species. Other differences between compounds for each species are described. The term excito-repellency has produced confusion in the literature, and it is revisited and discussed with respect to the results, which justify the use of alternative terminology. The term "locomotive stimulant" is offered as an acceptable alternative.