As spring approaches and temperatures begin to rise, overwintering stink bugs emerge from hiding to begin the reproduction process. The insects typically mate and produce eggs from May to August. Female stink bugs lay batches of 20 to 30 barrel-shaped eggs on the undersides of leaves. Eggs hatch into tiny black and red nymphs that measure less than an eighth of an inch. Nymphs progress through five instars before reaching adulthood. Fully grown stink bugs measure about one inch in length. Stink bugs usually produce one or two generations per year. However, temperatures influence reproduction rates, and warm spring and summer seasons can result in three to four generations in a year. Sub-tropical regions can see as many as six generations of stink bugs in one year. New England’s temperate climate usually limits stink bugs to one generation per year.
Stink bug populations spike as summers progress. During the fall, typically between September and October, the insects begin searching for overwintering sites. Outdoor stink bugs overwinter in piles of leaf litter and become active again when temperatures increase. Stink bugs may also enter homes to overwinter, often invading in large numbers. Warm temperatures inside the home keep stink bugs active, making them winter-long nuisances.