Although Box Elders specialize on Acer seeds, they may cause damage to plant tissues while feeding. They form large numbers while sunning themselves in areas near their host plant. They feed and lay eggs on maple and ash trees. During winter months, they sometimes invade houses and other man-made structures. They are inactive inside the walls ands voids while the weather is cool. Sometimes heating systems cause them to think it is spring and hatch early. They can be found in large number in the spring well into the fall. They become a problem when they seek warmth in houses and businesses looking for winter hibernation locations.