The boxelder bug is a common pest over much of the United States.  Adults are about 1/2 inch long, bright red or black in color with narrow reddish lines on their back.   These insects feed principally by sucking juices from the box elder tree, but are sometimes found on many other plants.  In most cases, box elder bugs cause no major damage inside homes, but their droppings stain curtains and other resting sites.   This bug also emits a foul odor when crushed.  Adult box elder bugs will enter homes in the fall, seeking winter shelter.  They will over-winter in protected areas, often in wall voids or in attics.  They will then emerge in the spring to seek out host trees on which to feed and lay eggs.  

Boxelder bugs do not bite, but their piercing-sucking mouthparts can sometimes puncture skin, causing slight irritation.   Their droppings make quite a mess and these pests can accumulate in great numbers in your home if left unchecked.  Warm temperatures (found in buildings such as your home) interfere with their natural cycles and biology, causing them to reproduce year-round in unwanted areas such as your home.