House Fly

 Adult house flies are about ¼ of an inch long.  They are dull gray with four longitudinal stripes on the thorax. They are most abundant in the fall but may be found throughout the year.  House flies are a nuisance, but are primarily a concern because they spread pathogens that cause disease in people and domestic animals.

Cluster Fly

The adult cluster fly may be mistaken for the house fly at first, but they are larger and have fine, yellow or gold hairs on the thorax. On sunny days from mid-fall to early spring, the flies buzz around noisily and sluggishly indoors.  Adult flies enter buildings in late summer and early fall through very small openings to find a place to hibernate, usually on the south and west sides.