What Are the Brown Bugs All Over Amherst?

People around town have been referring to them as stink bugs, and it seems as though this fall they are everywhere around town.

The good news is, these little brown invaders are not harmful, though they may be a nuisance.

They aren't actually stink bugs, though they stink if you crush them, said Jon Nute, an extension field specialist in the natural resources department at the UNH Cooperative Extension's Hillsborough County branch. They are western conifer seed bugs, Nute said, and thankfully the recent invasion is as harmless as a lady bug infestation. 

"They look offensive, but they don't bite, they don't do any damage to your home,” Nute said, calling the bugs a nuisance.

Like stink bugs, these guys give off an odor and they may leave a little brown stain on your wall if you crush them, Nute said.

Instead, Nute recommends releasing them back outside if they have sought warmer climes in your home, or vacuuming them up will do just fine.

According to a file on the UNH Cooperative Extension's website “The adult WCSB is a dull brownish color, about ¾-inch long, with a flattened leaf-like expansion on the hind legs and a faint white zigzag stripe pattern across the midpoint of its upper surface. When an adult insect takes flight, it lifts its wings to reveal bright yellow-orange areas on its back.

“In flight, the adults make a buzzing sound like a bumblebee.”

There are some measures you can take to try to prevent them from invading your home, especially if you're particularly squeamish about having unwanted insects in your home:

• Be sure to screen attic or wall vents, chimneys and fireplaces so you block their points of entry.
• Eliminate or caulk gaps around door and window frames and soffits
• Tighten up loose-fitting screens, windows or doors to prevent these insects from getting into your home.

The seed bugs feed on coniferous plants, according to the Cooperative Extension. Host plants include white pine, red pine, Scotch pine, Austrian pine, Mugho pine, white spruce, Douglas fir and hemlock. Due to the proximity of these types of plants to many New Hampshire homes, its likely that as the temperatures drop, they will seek shelter inside, read: your home.

And if you're wondering why all of a sudden there's been an explosion of these six-legged creatures, Nute said they are fairly new to the area.

“We never had them before,” Nute said. “As their name suggests, Western, they have come to us from other parts of the country.”

According to the University of Rhode Island, these bugs started expanding east, arriving in Western New York by 1990 and Rhode Island by 1996. Since then, they've continued to progress north.

The first one was recorded in New Hampshire in 1997 and they were first in Sullivan and Chesire counties, according to a document on the Cooperative Extension site. However, Nute estimated they didn't really appear in force in Hillsborough County until about five years ago

The bugs hibernate in warm spaces during the winter – inside buildings – and then head back outdoors as the weather warms up, to breed – so their numbers grow more and more each year.

Nute said last year's mild winter may have contributed to the higher numbers this year.

Nute suggested releasing the bugs outdoors, and taking steps to seal your home in order to keep them out. Because of their harmless nature, Nute advised against using harmful insecticides to kill them. Most insecticides are poisonous to people.

"I'd hate to have you spray insecticide all over the house when it's not necessary," Nute said.

*Editor's note: This story was first published in October 2012, but are republishing it with the return of the Western Conifer Seed bugs this fall.