Threecornered alfalfa hopper,Spissistilus festinus(Say), flight activity in alfalfa,Medicago sativaL., and diel activity in alfalfa and soybean,Glycine max(L.) Merrill, were monitored with yellow sticky traps and a rotary aerial sweep net. Movement was primarily within 33 cm above the soil surface. Amount of activity and numbers ofS. festinusincreased as alfalfa grew from stubble to harvestable plants. Activity was significantly greatest between 1000 and 1200 hours, during which temperatures averaged from 33.9 to 37.8°C. Limited flight occurred higher than normal during periods of greatest activity in alfalfa. Significantly more male than femaleS. festinuswere trapped on the sticky traps, contrasting with a more balanced sex ratio found in sweep net samples. Catches were apparently not affected by compass orientation of the sticky traps.