(Summary) Field observations on a population of Aedes triseriatus in southwestern Wisconsin revealed that: (1) biting activity increased from mid-June to a peak in the second half of August, (2) the greatest biting activity occurred in the afternoons before 6 PM, (3) mating occurred in both swarms and on a host, (4) oviposition occurred up to at least 20 ft above ground, and (5) peak oviposition activity occurred during a 2-hour period extending from 1 h before sunset to 1 h after sunset. Aedes hendersoni was found for the first time in Wisconsin.