Infestation
Flies gather in large numbers in wall voids and attics in the fall and winter; they move into living area and collect at windows during winter; flies move around house in winter. In churches, hospitals, and other buildings year after year.
Identification
Look like house flies, except the thorax has yellow hairs; the wings are crossed at the back when at rest. Gather on the sides of houses in fall.
Control
Pyrethroid spray to attic walls and ceiling may help, repeat application in mid winter. 'No pest' strips in attic may give control. Avoid spraying the sides of houses and buildings.
