Engorgement rates were determined for nulliparous and uniparous Ae. triseriatus enclosed with unrestrained chipmunks and grey squirrels in a large laboratory cage. Animals exposed singly permitted a lower proportion of full engorgements by nulliparous mosquitoes than did animals exposed as pairs, ranging from 6 to 24% for the former compared to 60-64% for the latter. Uniparous females were only about half as successful in obtaining complete blood meals from individually exposed animals as were nulliparous females and fewer than half as many uniparous as nulliparous non-engorged females enclosed previously with individually exposed hosts launched a post-test attack when a non-defensive human was offered. Implications relative to La Crosse virus epidemiology are discussed.