Studies were conducted to evaluate factors that mediate flight performance and behavior of the mosquito, Aedes triseriatus. The laboratory (tethered) flight ability of Ae. triseriatus was evaluated under standard laboratory conditions. Ae. triseriatus was a strong flier. The length (distance) of exhaustive flights increased as mosquitoes aged from week 1 (5,805 m) to week 3 (9,910 m). Older mosquitoes were much slower fliers. Live weight did not affect flight ability. Virgin, gravid, and parous mosquitoes exhibited different tethered flight abilities. Uniparous and biparous mosquitoes did not fly as far as virgin or gravid mosquitoes;The circadian flight activity of Ae. triseriatus following insemination, blood-feeding, and oviposition was evaluated under a 16:8 light/dark cycle. Aedes triseriatus had a bimodal activity pattern. Mosquitoes were inactive through all but the last four hours of the photophase, with the primary activity peak near lights off; a second, smaller activity peak occurred at lights on. Peak activity of virgin and blood-fed virgin mosquitoes occurred during the hour prior to lights out, whereas inseminated and blood-fed inseminated females were most active in the hour after lights out. Inseminated and blood-fed inseminated mosquitoes were 53 and 40% less active, respectively, than their virgin and blood-fed virgin counterparts. Parous mosquitoes resembled inseminated nulliparous females in the level and pattern of spontaneous activity;The spontaneous flight activity of Ae. triseriatus orally infected with La Crosse (LAC) virus was monitered (18-23 days postinfection) to determine if circadian rhythm and/or level of spontaneous flight changes when this species is infected with LAC virus. The endogenous activity pattern (circadian rhythm) was identical in both noninfected controls and LAC infected mosquitoes. However, the LAC infected mosquitoes were 24% less active, initiated 36% fewer spontaneous flights, and their total flying time was 34% less than that of control mosquitoes.