INTRODUCTION.
These flies receive the common name of house from being the most common fly found
in and around homes, especially in the preautomobile era and in rural areas. It is not
only a nuisance pest but of greater concern is its potential as a carrier of disease
organisms, having been found to harbor over 100 different pathogenic organisms. It is
worldwide in distribution, and is found throughout the United States.
RECOGNITION.
Adults about 1/8- 1/4" (4-7.5 mm) long, with female usually larger than
male. Color dull gray; face with 2 velvety stripes, each silver above and gold below;
thorax with 4 narrow black longitudinal stripes on dorsum; no pate spot behind head or on
scutellum (rear tip of thorax); abdomen usually with sides pale at least near base.
Mouthparts sponging. Females with eyes much more widely separated than on male. Wing with
4th (3rd long) vein (M) sharply bent forward near tip, towards and almost meeting 3rd vein
at wing margin.
Mature larva about 1/4-3/8" (7-10 mm) long; eyeless, legless, and
tapering towards head from large rounded rear segment, head represented by 1 pair of dark
hooks. Color cream but with greasy appearance. Posterior spiracles (breathing pores)
slightly raised, spiracular area smooth, spiracular openings are sinuous/winding slits
which are completely surrounded by an oval black ridge (peritreme) which has a dark
donut-shaped structure (button or ecdysial/molting scar) attached to its inner margin.
SIMILAR GROUPS.
Face fly (Musca autumnalis) have wing calyptera (flat basal lobe)
with tuft of bristles; males with eyes almost touching (vs. well separated with
parallel-sided frontal stripe between) and abdominal dorsum and sides entirely black in
ground color with gray-and-black (vs. usually yellowish at sides) whereas, female with
parafrontals (sides of front next to eyes) bright gray, nearly as wide as median frontal
stripe (vs. often yellowish, about 1/3 as wide as frontal stripe).
Flesh flies (Sarcophagidae) have only 3 dark longitudinal stripes on
thorax, tip of abdomen usually red/pink, abdominal sides never pale.
Stable (Stomoxys calcitrans) and false stable (Muscina stabutans)
flies have wing with 4th (3rd long) vein curved towards 3rd vein but not sharply angled;
in addition stable flies have piercing mouthparts and thorax with pale spot behind head
while false stable flies have sponging mouthparts but a pale soutellum (rear tip of
thorax).
Cluster fly (Pollenia rudis) with golden hairs on thorax, thorax
lacks 4 dark longitudinal stripes.
Little house (Fannia canicularis) and latrine (F. scalaris) flies
have wing with 4th (3rd long) vein straight.
Other flies either lack 4 dark thoracic stripes, 4th (3rd long) vein
sharply angled, and/or dull thorax and abdomen.
BIOLOGY.
The adult female lays her eggs (white, oval, 1/32"/l mm long) singly but usually in
clusters of 20-50 for a total of 75-150 per batch and will lay 5-6 batches in her lifetime
totaling 350-900 eggs (maximum 2,387 in 21 batches). Eggs are laid in moist materials,
hatch in about 8-20 hours, and the larvae (maggots) go through 3 instars in 3- 7 days at
70-90'F (21-32'C). The full-grown/mature larva seeks a cool, dry place to pupate,
migrating up to 150 feet in 3-4 days. The pupa starts out yellowish and changes to black,
this stage taking 3 days to 4 weeks depending on temperature and humidity. After emerging
from the pupa, about 1 hour is spent drying the wings and hardening the body at 80'F
(27'C), with normal activity starting at 15 hours. Depending on conditions, developmental
time (egg to adult) may require as few as 6 days. There may be as many as 10-1 2
generations per summer. Adults usually live 15-25 days.
House flies are general feeders, being attracted to a wide variety of
substances from excrement to human foods. Because of their sponging mouthparts, they can
feed only on liquids. However, through regurgitation they are able to liquefy many
desirable solid foods. Also, a house fly excretes and regurgitates whenever it comes to
rest. This habit coupled with its many body hairs and bristles and the sticky pads at the
base of the claws on each leg make house flies well adapted for transporting disease
organisms.
House flies have been shown to harbor over 100 different kinds of
disease causing pathogens, many of which are associated with filth. Such pathogens include
those causing typhoid fever, cholera, diarrhea, dysentery, tuberculosis, anthrax,
ophthalmia, polio, and salmonellosis, as well as parasitic worms. They have been shown to
be disease pathogen transmitters via their vomit, feces, and contaminated external body
parts.
HABITS.
Although house flies have been shown to migrate up to 20 miles, most stay within 1-2
miles/1.6-3.2 km (55-96% within 1 mile, 77-100% within 2 miles) of their release point or
larval habitat if sufficient food is available. Females seek almost any warm, moist
material with sufficient food for larval development for egg-laying purposes.
During the day, house flies tend to rest less than 5 feet (1.5 m) from
the ground on walls, floors, and various objects. At night they rest primarily above 5
feet (1.5 m) on ceilings, walls, electric wires, dangling light cords, edges/corners of
buildings, plants, etc. Their night resting places are usually near their daytime food
sources.
