Lots of them, but what are they?

Vacaville residents Mark and Julie Vasquez began finding little flies in Birds Landing, near Rio Vista, in late January 2009.

Their numbers are increasing rapidly.

“They’re everywhere,” said Mark. “They’re in our storage shed and inside Julie’s parents’ home and grandmother’s home. They were under my rubber boots in the storage shed.”

“They come every year and get into everything,” Julie told Mark.

Everything—including Mark’s parked pickup truck. Last weekend the flies slipped through the vents and inside the cab. With no "thumbs up," they hitched a ride from Birds Landing to Vacaville.

"Some are still flying around in the cab," Mark said.

What are they?

The picture-winged fly (Ceroxys latiusculus). Order: Diptera. Family: Ulidiidae.

The insect is about the size of a house fly, but doesn’t move as fast, as Mark can attest. He captured a dozen in a jar.

Little is known about the biology of this common fly, but it's often confused with the walnut husk fly.

Entomologist Whitney Cranshaw of Colorado State University says this about the picture-winged fly "It's a moderate sized fly (9-12 mm) about the size of a house fly. Its general coloration is grayish-brown but the most notable physical features are the the wings which have dark patterned markings."

Cranshaw says the picture-winged fly is commonly found indoors from early fall through spring. It is most often noticed around windows.

Meanwhile, several of the little buggers are still flying around in the cab of Mark's truck.