At George Lake, 63 km northwest of Edmonton, Alberta, from April to September 1973-75, mosquitoes were caught from cattle in the open and from a calf-baited stable trap. Mosquitoes of 15 species or species groups were collected in nearly the same proportions in the stable trap as on cattle in the open. Combined attack rates of all species were highest in late July and early August when the mosquitoes arrived at a tethered calf faster than they could be collected. The stable trap caught more mosquitoes, but still underestimated the relative abundance of some species because it hindered their entry. The most abundant mosquitoes were Aedes vexans, Ae. communis group, Culiseta inornata, Cs. alaskaensis, Ae. spencerii, Ae. fitchii group and Ae. flavescens. Cattle in fields were severely disturbed by mosquitoes in late May (chiefly Ae. spencerii), and from mid-July to early August (Chiefly Ae. vexans, Ae. spencerii and Cs. inornata).