The brown marmorated stink bug (BMSB), though accidentally introduced into the U.S., is one of many species of stink bugs that can be found here. They are the typical “shield” shape of other stink bugs, almost as wide as they are long. The BMSB is about 17 mm long (equal to about .7 inch) and is distinguished from native stink bugs by the white banding on its antennae and legs, along with its marbled appearance (the alternating black and white pattern on the sides of its abdomen; “marmorated” means marbled).
The two seasons when people most notice the bugs are in the fall — when they come inside homes looking for warmth and shelter — and in the spring, when they look for ways to come out of hiding.
Adults begin to search for overwintering sites starting in September through the first half of October. The best way to prevent stink bugs from entering your home is to seal up any openings through which they can enter. Cracks around windows, doors, siding, behind chimneys, and underneath fascia and other openings should be sealed with good quality silicone or silicone-latex caulk. Weather stripping around doors and windows may also help. A foam sealant can be used if there are small openings where pipes or wires enter the house. Lastly, damaged screens should be repaired or replaced, and window and wall air conditioners should be removed or sealed off.
In the fall, once they find their way in, stink bugs tend to head toward the attic. However, they may congregate almost anywhere, such as within stacks of newspapers or bookcases; under beds and sofas; in cracks under or behind baseboards, window, and door trim; and in piles of clothes. Thankfully, they will not cause structural damage or reproduce in your house. They are simply looking for a place to survive during the winter.
The emergence of adult bugs from overwintering sites can begin in mid-April if temperatures are suitably warm. Emergence tends to peak from about mid-May to early- to mid-June and taper off by the end of June.
When temperatures start to warm in the spring, and sunlight is brighter, stronger and warmer, stink bugs will begin to find their way out. It is a good idea to try to locate any openings they can come out of and seal them off. Typically, stink bugs will emerge from cracks under or behind baseboards, around window and door trim, and around exhaust fans or lights in ceilings. Seal these openings with caulk or other suitable materials to prevent the insects from crawling out.