Identifying characteristics
The Fanniidae were once a subfamily of Muscidae from which they may be distinguished by:
A (strictly) dorsal bristle is on the hind tibia below the middle and in addition to the dorsal preapical. The axillary vein is strongly curved towards the wingtip, so if extended, the axillary and anal veins would meet before reaching the wing tip. In males, the middle tibia has an erect pubescence beneath; in females, the frontalia is without crossed bristles, the frontal orbits are broad, and convex towards median line of frons, and two pairs of strong upper orbital bristles are present, with the anterior pair turned outwards.
