Where do stinkbugs lay their eggs?

Now that fall’s here, stinkbugs are starting to appear inside again. A patron called asking about their lifecycle and reproduction, hoping to catch them before they hatched.

Brown marmorated stinkbugs only arrived in the U.S. in the late 1990s, but they’re a widespread pest now. We found a lot of information online, such as the Washington Post livechat with University of Maryland entomologist Michael Raupp, and pest control websites like AssuredEnvironments.com and Terminix.com.

Stinkbugs like to come inside to stay warm through the winter, but they don’t eat or reproduce until they go back outside in the springtime again. Once the weather gets warm and the days get longer (usually in April or May), you’ll see them appear again as they make their way outside to feed for a few weeks and then mate. A female will be ready to lay eggs as early as five days after mating, according to AssuredEnvironments.com, and she can lay from 100 to 400 in her lifetime. (We found different figures – it probably depends on the climate of the state where she’s found. A stinkbug in warmer climes will be outside eating and reproducing longer.)

The stinkbugs will only lay their eggs on the underside of leaves. The eggs are barrel-shaped and about a millimeter in diameter. The female lays twenty to thirty at a time and they take four to seven days to hatch. It takes a little over a month for the baby bugs (or nymphs) to grow into full adults – they go through five stages (or instars) before they’re fully grown, each lasting about a week. When they first hatch, they don’t look much like the adult bug. First instar stinkbug nymphs are rounder, resembling ticks, and black and orange in color.

If you come across these eggs or nymphs underneath a leaf, you can scrape them off and drown them in soapy water. (This also works on the adult bugs and keeps them from releasing their smell.) Scientists in New York and Oregon, where the bugs cause a lot of agricultural damage, are experimenting with biological control in the form of samurai wasps. These tiny parasitic wasps lay their eggs inside stinkbug eggs, killing them before they can hatch.

If nothing else, you can take comfort in knowing that stinkbugs only live for about six to eight months, and the bugs bothering you this fall won’t be back next year – but their children might.