Stink bugs are recognized for the distinctive odor they release when disturbed and their shield-shaped bodies. The brown marmorated stink bug (BMSB), an invasive species from Asia, is frequently encountered in residential areas across North America. Understanding their life cycle helps explain their seasonal presence and longevity.
The Stink Bug Life Cycle
The life cycle of a stink bug involves three main stages: egg, nymph, and adult, a process known as incomplete metamorphosis. Female stink bugs typically lay clusters of 20 to 30 barrel-shaped, light green eggs on the underside of leaves, usually from May through August. These eggs generally hatch within 4 to 7 days, releasing tiny nymphs.
Nymphs are wingless and progress through five developmental stages, called instars, each typically lasting about one week. They grow in size from approximately 2.4 millimeters in the first instar to around 12 millimeters by the fifth instar, with their coloration changing as they develop. After completing the nymphal stages, they undergo a final molt to become winged adults. The entire development from egg to adult can take approximately 40 to 60 days, depending on environmental conditions.
Once they reach adulthood, stink bugs can begin reproducing within about two weeks. In cooler regions, a typical stink bug population completes one generation per year, while warmer climates can support two to three generations annually. Adult brown marmorated stink bugs generally live for about 6 to 8 months.
Factors Influencing Lifespan
Several factors influence a stink bug’s lifespan. Temperature significantly impacts their development and survival; warmer conditions accelerate their life cycle. However, excessively high temperatures can be detrimental, reducing survival rates. Colder climates lead to shorter active lifespans and compel them into dormancy.
Humidity also plays a role in survival; higher humidity benefits early nymphal stages but decreases survival for later instars. Availability of food sources, such as various plants and fruits, directly affects their longevity and reproductive capacity. Brown marmorated stink bugs feed on a wide range of plants, including many economically important crops.
Natural predators and diseases regulate stink bug populations. Birds, bats, spiders, assassin bugs, and parasitic flies prey on stink bugs. Parasitic wasps, particularly those that target stink bug eggs, are biological control agents, though native parasitic wasps may not be highly effective against invasive species like the brown marmorated stink bug.
Overwintering and Seasonal Presence
As temperatures drop and daylight hours shorten in the fall, adult stink bugs enter a state of dormancy known as diapause. This inactivity allows them to conserve energy and survive cold winter months. During this time, they seek sheltered locations to overwinter.
Many find refuge indoors, congregating in attics, basements, wall voids, or small cracks and crevices. Outdoors, they may overwinter under leaf piles, logs, or within the bark of dead trees. While dormant, they pose no threat to structures or indoor food sources.
As spring arrives and temperatures rise, stink bugs emerge from overwintering sites, becoming active. They then seek out food and begin their reproductive cycle. This seasonal behavior explains why these insects appear to “last” for an extended period, especially when emerging inside homes in spring after winter dormancy.