Social wasps show swarming tendencies when their habitats are threatened. Examples include paper wasps, yellow jackets and hornets. The aggressive yellow jackets resemble honeybees with their yellow and black markings, although they have much narrower abdomens. They build nests on tree stumps, fallen logs and earth mounds, and have painful stings that can cause bacterial infections as well as allergies. Paper wasps have reddish-brown, red, orange or yellow stripes and live in nests with paper-like cells. Though protective of these nests, they are slow and comparatively docile. Hornets, the most aggressive among social wasps, build large, football-shaped nests. These nocturnal yellow-and-chestnut-colored insects reportedly attack even upon the slightest provocation.