Attack of the moths: Lawmakers watch out

Lawmakers last week were brushing moths off their lapels, but not because they’d left their suits in the closet too long.

Up around the ceilings on both the House and Senate sides, moths flapped along the paintings. Outside on the Capitol steps, dead moths lay strewn about. Neither security guards nor staff of the Architect of the Capitol (AoC) knew where they came from.

Donald Davis, a research entomologist for the Smithsonian, said he needed to examine the specimens to determine whether the plague of moths on the Hill was part of an outbreak, which he says would be very rare. Instead, he said, it’s most likely that there has been a drop in parasites, the moths’ predators.  

The women at the appointment desk on the Senate side wrinkled their noses when talking about the flying beasts they had seen zooming around. “Feels like Hitchcock!” they said, glancing at the ceiling.

An AoC employee knocked a moth off his shoulder without so much as a funny look or pause. Capitol security guards crunched the bugs under their shoes and offered their own explanations. “There must be a nest around here,” said one guard, peering up under the portico, where the sun baked the dead moths onto the granite.

Another expert, John Lill, assistant professor of biology at George Washington University, suggested that they are emerging Eastern Tent Moths. But he said he had not examined any Capitol Hill specimens himself yet.

“They’re flying in very large numbers right now,” Lill said. “There was a large number, but not an outbreak, of Eastern Tent caterpillars this spring.”

The caterpillar larvae have gone through metamorphosis and are now emerging as adult moths, Lill explained. He has noticed them swarming around the moth lights he sets out at night.

Eastern Tent Moths live off of cherry tree foliage, as well as crabapple foliage, which is common around the Hill. That may explain why so many appeared last week. The moths are not dangerous to humans, but they can cause some damage to plants and trees, mainly because of the nests they build and the leaves they eat.

Another entomologist working with the Smithsonian, John Brown, agrees they are hard to miss. “My bucket trap was just full of them,” he said.  

But Lill says it’s hard to guess what these Hill moths might be or where they came from. “It’s been kind of cool this past week, so it hasn’t been the best mothing weather,” he said.