Dark beetles on the march across south Tri-Cities. Here is why there are so many

Darkling beetles are back, marching north across Tri-Cities sidewalks and roadways, particularly in places where residential neighborhoods meet undeveloped land in south Kennewick and Richland.

Each year in late summer the bugs show up, and there may be more of them than usual this year.

Insect activity may be high now because of the lack of long cold spells last winter that would have killed off bugs, followed by a hot summer, said Stacey Abney, a Washington State University Extension master gardener.

Some years the black beetles show up in the Tri-Cities gradually over months and their migration may go unnoticed. But other years they migrate in large numbers traveling in a single direction.

This is one of those years and they are right on schedule. Past Tri-City Herald articles show that when they show up suddenly in large numbers it is usually the third week of September.

In 2008, there were so many beetles in the third week of September that one couple was sweeping their driveway three times a day and sucking up the beetles with a shop vacuum cleaner, the Herald reported then.

Another Kennewick woman said that year that she and her husband saw how many beetles they could squash in one crunchy step on an evening walk. Eight was the record.

The beetles are common in desert regions and “nothing to be concerned about,” Abney said.

Some other beetles are more beneficial because they feed on harmful insects. The darkling beetle feeds on decaying plant matter such as dead leaves and rotting wood.

The darkling beetles may be of the Tenebrionidae beetle family , which includes more than 15,000 species, WSU Extension has previously told the Herald.

Getting rid of them

It said that insecticide sprays may not be successful against them, but residents can just sweep them off areas where they don’t want them and wait out the the migration, which will be over in a couple of weeks.

During the hottest part of the day they may move to cool, moist and dark places, such as under rocks and garden debris.

The black or dull brown darkling beetles’ wing covers are fused so they are unable to fly and must spend their lives on the ground.

Entomologists may identify them through their antennas, which are segmented into 11 parts and slightly clubbed on the end.

Darkling beetles also may be known as stink beetles, long-time Herald garden columnist Marianne C. Ophardt told readers in 2004.

If they are disturbed or threatened they will stick their rear end up in the air and a dark, foul-smelling liquid eases out, she wrote.

“The fluid is stinky enough to ward off potential predators, such as snakes, birds, rodents, raccoons, coyotes and foxes,” she wrote. “This is a particularly effective defense, especially for the large darkling beetle species.”

However, some Tri-Cities residents were reporting on social media this week that their dogs were gobbling up the darkling beetles.