Size
House fly adult is about 1/8-1/4 in (4-7.5 mm) long, female
larger than male. Mature larva is about 1/4-3/8 in (7-10mm).
Characteristics
Adult face has 2 velvety strips, silver above and gold below;
thorax has 4 narrow stripes; no pale spot behind head or rear
tip of thorax; sides of abdomen usually pale; sponging mouth parts.
Larva is eyeless, legless, tapered from rear to head, which is
a pair of dark hooks.
Color
Adult is dull gray. Larva is cream colored and greasy looking.
Comparison with other species
Face fly males have eyes that almost touch. Flesh flies have
only 3 dark stripes on thorax, and tip of abdomen usually red/pink,
sides of abdomen not pale. Stable flies have piercing mouthparts
and thorax with pale spot behind head. False stable flies have
pale rear tip of thorax. Cluster fly has golden hairs on thorax,
which lacks 4 dark stripes.
Habitat
Females lay eggs on almost any warm, moist material with
adequate food supply for egg-laying and larval development. Most
house flies stay within 1-2 miles of their larval habitat if food
is available, though some have migrated up to 20 miles. During
the day, they rest less than 5 ft. from the ground; at night,
mainly above 5 ft., but near their food sources.
Food
House flies are general feeders on liquids; attracted to
many substances, from excrement to human foods. House flies can
liquefy solid foods by regurgitation.
Biology
Adult female lays oval, white eggs singly in clusters of
20-50, laying 350-900 eggs in her lifetime. Eggs hatch in 8-20
hours. Larvae go through 3 instars in 3-7 days at 70-90 degrees
F. Full grown larvae go to a cool, dry place to pupate, traveling
up to 150 feet in 3-4 days. Pupa goes from yellowish to black
during a period of a few days to a month, depending on temperature
and humidity. After emerging, the body hardens and the wings dry
within about an hour. Development from egg to adult can be as
few as 6 days, with 10-12 generations per summer. Adults live
15-25 days.
Damage
House flies excrete and regurgitate whenever stopping to
rest. They have many hairs and bristles, as well as sticky pads
at the base of the leg claws. Therefore, they tend to transmit
disease organisms, especially those associated with filth.
