Stink bugs come by their name honestly, releasing an acrid odor when threatened or killed. They don't live in colonies or family groups, so you won't typically see more than just one stink bug. However, stink bugs are prolific and tend to congregate in areas where there's sufficient food -- so it's likely that one stink bug is simply the harbinger for many.
Stink Bug Infestations
One of the biggest stink bug pests, the brown marmorated stink bug, hails from Asia but appeared in the late 1990s in the United States. Since then, it's spread to at least 39 states, according to the Science Daily website. It has few natural predators in the United States. With each female capable of laying up to 400 eggs in a single summer, the populations often grow to infestation sizes. This can wreak havoc in your fruit trees or vegetable garden, and the bugs often come inside your home for a warm place to spend the winter -- usually in large numbers.