The Brown Marmorated Stink Bug (BMSB) is a nuisance pest known for invading homes as temperatures drop. As an invasive species, this shield-shaped insect’s survival relies on a dramatic shift in behavior linked to the changing seasons. Understanding their winter life cycle helps explain why they seek shelter in human dwellings as summer ends. Their seasonal activity dictates a complete metabolic pause, which is the key to their overwintering success.
Autumn Feeding Habits and Energy Reserves
Before cold weather, the BMSB engages in intense, opportunistic feeding to prepare for survival. Throughout the summer, these pests feed on a wide variety of plants, including agricultural crops like apples, peaches, corn, and soybeans, along with many ornamental trees and shrubs. As daylight hours shorten in late summer and early autumn, their focus shifts from reproduction to energy storage.
This pre-winter phase involves consuming large amounts of food to maximize energy reserves, primarily stored as lipids, glycogen, and sugars in their fat bodies. These stored nutrients are accumulated solely to fuel the insect through the entire winter period. The quantity of these reserves determines the bug’s likelihood of surviving until spring, as they cannot replenish them once the cold sets in.
The Biological State of Winter Diapause
Contrary to common belief, stink bugs do not eat during the winter months. Their survival is secured by entering a biological state called diapause, a form of metabolic suppression triggered by decreasing photoperiod and cooler temperatures. Diapause is a pre-programmed state of developmental arrest that is distinct from simple hibernation, involving a profound physiological slowdown.
Once in diapause, the insect’s metabolism drops significantly, conserving the energy stored in its fat reserves. Reproductive activity is arrested, and the need for food is eliminated. The bug relies solely on the lipids and carbohydrates accumulated during the autumn feeding frenzy. The BMSB is not feeding on house plants, wood, fabric, or stored food products while overwintering inside a structure.
This physiological state enables the stink bug to survive without sustenance for several months. While they may lose some glycogen and sugar reserves over the course of the winter, their suppressed metabolic rate ensures the reserves last until the weather warms. An increase in temperature can cause them to briefly become active, but they will not resume feeding until they exit the overwintering site in the spring.
Preferred Overwintering Locations
The primary goal of the BMSB in late fall is to find a stable, protected location where they can safely undergo diapause without freezing. Naturally, they seek shelter in dry crevices, such as under the loose bark of dead trees or within rocky outcroppings. The common sight of them inside homes is a direct result of this shelter-seeking instinct, as human structures provide superior protection from the elements.
Stink bugs enter buildings through any available crack or gap, often flattening their bodies to squeeze through tight spaces. Common entry points include openings around window and door frames, utility penetrations, roof flashing, and unscreened vents. Once inside, they migrate to upper areas of the structure, such as attics, wall voids, and unused chimneys. These locations offer the cool, dry, and protected environment necessary to maintain their state of metabolic suppression.