Adults overwinter and emerge in late April or May depending on the temperature. Adults have been reported in 1998 since the third week of April. Some bean leaf beetles are red instead of yellow. Bean leaf beetles look much like black-spotted yellow, brown, or brick red lady beetles. Unlike lady beetles, bean leaf beetles have a prominent black triangle at the front of the wing covers that points backward and most, but not all, have a series of rectangular spots on the wing covers.
Adults occur in two color phases, red and yellow.
Bean leaf beetles have the noticeable habit of abruptly dropping to the ground and scurrying into cracks and crevices when disturbed. Crop scouts need to approach infested plants carefully and watch for this behavior to estimate population size effectively. Bean leaf beetles feed on a variety of legumes but immediately following emergence they are most commonly found on alfalfa. The beetles often move to soybeans within 3 days of soybean seedling emergence. This colonization of soybean is typical in Iowa, but because the overwintering bean leaf beetle population is usually low, beetles often are not obvious on young soybean plants.