The brown marmorated stink bug (Halyomorpha halys) is an invasive insect, native to Asia, that has become a widespread nuisance pest in North America. The duration of their presence inside a home is directly tied to the adult bug’s biological need to survive the colder months in a protected environment.
The Complete Life Cycle
The progression from egg to reproductive adult typically occurs once per year in temperate regions, though warmer climates may support multiple generations. The female lays light-green eggs in clusters of 28 on the underside of host plant leaves, generally from late spring through mid-summer. The egg stage is the shortest, lasting only 4 to 5 days before the first-stage nymphs emerge.
The insect passes through five distinct nymphal stages, or instars, during a period of growth and development that takes approximately 40 to 60 days to complete, depending on ambient temperatures. These nymphs are wingless and gradually increase in size while developing the characteristic black and white banding on their legs and antennae. The final molt transforms the fifth-instar nymph into a winged, sexually mature adult, which begins to appear by late summer or early fall.
Adult Lifespan and Overwintering Survival
The adult stage is the longest-lasting phase, with individuals surviving for an average of six to eight months. Adults that develop in late summer are responsible for the home-invasion nuisance, as their survival centers on a dormant state called diapause. This overwintering period accounts for the majority of the adult’s lifespan, which can last up to a year.
Diapause is triggered by environmental cues, primarily decreasing day length in late summer and early fall, with cooling temperatures playing a synergistic role. This physiological shift causes the adult to cease reproductive activity and suppress its metabolism to conserve energy. Only adults are capable of entering this dormant state, and they actively seek sheltered locations to avoid freezing temperatures.
Why They Invade Homes and When They Depart
The motivation for moving into human structures is the need to find a thermally stable, protected site for diapause, as the bugs cannot survive harsh winter conditions outdoors. Movement into homes begins in late summer and early fall, as decreasing temperatures signal the need for an overwintering site. They gain entry through cracks, gaps around windows and doors, utility penetrations, and vents, often aggregating in attics, wall voids, and soffits.
Once inside, the bugs remain largely inactive through the winter, neither feeding nor reproducing. The nuisance period ends in the spring when increasing temperatures and day length signal the termination of diapause. Surviving adults emerge from their overwintering sites and attempt to leave the structure to seek food and begin mating outdoors. Those that survive the winter typically depart between March and May.