Stink bugs develop from egg to adult in roughly 40 to 60 days, passing through five distinct nymphal stages before reaching their full winged form. The entire cycle, from the moment eggs are laid to the point those new adults begin laying eggs of their own, requires about 686 accumulated degree-days of warmth. Temperature and day length drive everything: how fast they grow, how many generations appear each year, and when they hunker down for winter.
Eggs and Where They’re Laid
A female stink bug lays her eggs in tight clusters on the undersides of leaves. Each cluster contains about 28 eggs, and a single female can produce between 2 and 15 of these clusters over her lifetime. That means one female may be responsible for anywhere from roughly 56 to 420 offspring. After overwintering, females emerge in spring, feed on developing flowers and fruits to rebuild energy reserves, and then begin laying eggs on nearby host plants.
Five Nymphal Stages
Once eggs hatch, the tiny nymphs that emerge look nothing like their parents. They’re oval, wingless, and somewhat tick-like. First-stage nymphs are only about 2.4 millimeters long, with black heads and bright orange-red abdomens. They stay clustered near their egg mass for a short time before dispersing to feed.
Each of the five nymphal stages (called instars) lasts about one week, with the nymph shedding its exoskeleton between each one. After the first molt, most of that orange-red coloring disappears. Second-stage nymphs are dark with rough, spiny projections along the edges of their upper body. As they continue molting through the third, fourth, and fifth stages, wing buds gradually develop and become more visible. Later-stage nymphs take on a black-to-gray base color with noticeable white bands on their legs and antennae. Those leg bands are actually more prominent on nymphs than on adults, which can help you tell them apart.
Both nymphs and adults feed the same way: they use piercing, straw-like mouthparts to puncture plant tissue and suck out fluids. Even young nymphs cause crop damage, though adults tend to be more mobile and spread to new host plants more readily.
Adult Stage and Reproduction
After the fifth and final molt, the nymph emerges as a fully winged adult. Adults are the familiar shield-shaped, mottled brown insects most people recognize. They can fly, which dramatically increases how far they spread and how many plant species they feed on. Host plants range from fruit trees and soybeans to ornamental shrubs and a wide variety of weeds. When preferred wild plants dry out and become less attractive, adults migrate to crops like soybeans, where their feeding punctures developing pods and causes seeds to become shriveled, discolored, or undersized.
In warmer southern climates like Georgia, two full generations can develop per year. The nymphs from overwintering adults mature into summer adults by late July or August. Those summer adults then lay eggs that produce a second generation, which matures into new overwintering adults by September or October. In cooler northern regions, only one generation per year is typical. Climate data from Switzerland illustrates this pattern clearly: south of the Alps, two generations develop regularly, while north of the Alps, one generation is the norm, though unusually warm years can push northern areas into two-generation territory.
How Temperature Controls Development Speed
Stink bugs need a minimum temperature of about 62.6°F (17°C) to develop, and development stalls above roughly 91.4°F (33°C). Between those thresholds, warmer temperatures mean faster growth. Complete development from egg to adult requires 538 degree-days (a measure of accumulated heat over time), and reaching reproductive maturity takes an additional 148 degree-days. So the full egg-to-egg cycle needs 686 degree-days total. In a hot summer, that threshold is reached quickly, allowing two generations. In a mild summer, it may only be reached once.
Overwintering and Diapause
As days shorten in autumn, adult stink bugs enter a state called diapause, a form of dormancy triggered primarily by day length. When daylight drops to roughly 11 to 13 hours, their metabolism slows significantly and females stop developing eggs. This isn’t simply sleeping through winter. It’s a physiological shift that prepares their bodies for cold tolerance, though they still need a period of gradual cooling afterward to reach maximum cold hardiness.
To survive, overwintering adults seek sheltered spots. In nature that might mean under bark or leaf litter, but they strongly prefer human-built structures, which is why they famously invade homes and buildings each fall. They aggregate in crevices, behind siding, in attics, and inside wall voids. Cedar shingle siding, for example, provides the kind of tight gaps they favor.
Their cold tolerance has real limits. Stink bugs are chill-intolerant, meaning a portion of them die before temperatures even reach freezing. Exposure to temperatures between 14°F and 5°F (-10°C to -15°C) causes survival rates to plummet, dropping by 73% or more in field populations. In one study of outdoor populations in central Washington State, 100% of locally sourced stink bugs died by the end of January. Every individual that actually froze solid died. This is why access to insulated buildings can be the difference between a population surviving the winter and being wiped out entirely.
Spring Emergence
In spring, increasing day length reverses diapause. The critical photoperiod for diapause termination falls somewhere between 12.7 and 13.5 hours of daylight, depending on the population. As days lengthen past that threshold and temperatures warm, adults leave their sheltered overwintering sites. Their first priority is food: they seek out early-season flowers, buds, and developing fruits to restore energy before mating and egg-laying begin, restarting the cycle.