The boxelder bug (Boisea trivittata) is a North American species of true bug that is found primarily on boxelder trees, as well as maple and ash trees. They are about 13 millimeters long with a dark brown or black coloration, relieved by red wing veins and markings on the abdomen; nymphs are bright red. Boxelder bugs feed almost entirely on the developing seeds of boxelder, maple, and ash trees, but they can also suck leaves. They can be frequently observed on maple as these trees provide them with seeds as well. Boxelder bugs are not harmful to humans, but they can be a nuisance because they enter homes and other buildings, often in large numbers, during fall to find a warm place to hide for winter. They are attracted to buildings with a lot of southern or western exposure and like warm areas. Boxelder bugs are "true bugs" and belong to the same family as stink bugs, cicadas, and other insects with piercing and sucking mouthparts. They release a bad odor when crushed. Boxelder bugs overwinter in plant debris and emerge in late March to early April when the boxelder buds open. If boxelder bugs frequently invade homes, sealing up entry points such as cracks and screen windows and doors can help reduce their numbers.