Adult -- Lesser house fly is a term denoting flies
in the genus Fannia. Though similar to house flies, lesser house flies
have more slender bodies and a more hovering and jerky pattern of flight,
these are the ones that do your head in when they fly around the light
fitting in the middle of the room. About 5 to 6 mm long, the little
house fly has three brown stripes on its thorax and a yellowish abdomen.
Egg -- Eggs are white, narrow, elongate and slightly
flattened and are 2 mm long. They have wing-like processes which enable
them to float in liquids.
Larva -- Fannia maggots have many dorsal and lateral
projections and develop through three instars. About 1.5 mm long when
newly hatched, the first instar of the little house fly larva is white
with only the tip of its mouth hooks black. The second instar is about
3 mm long at first and has a little more black coloration. When mature,
the larva has a 5 to 8 mm long, light brown body with an entirely black
Pupa -- Slightly smaller than mature larvae, the pupae
of lesser house flies develop inside the darkened, hardened skins (puparia)
of the last larval instar.
Distribution -- Little house flies occur throughout
this country, and both species are common in homes, barns, stables,
and poultry houses in spring and autumn.
Feeding Habits -- Adult flies feed on various liquids
and are often attracted to aphid-infested plants by the presence of
honeydew (a sweet, sticky aphid excretion). Larvae typically consume
decaying organic matter and excrement but have been known to parasitize
the intestinal tract of man and animals. In some areas, lesser house
fly larvae are the predominant maggots breeding in chicken manure.
Damage -- Fannia spp. Flies are primarily an annoyance.
Like common house flies, little house flies breed in garbage and manure
and may transfer disease-causing organisms to human food such as dysentery
bacilli. In addition, larvae of this species have been known to develop
within the intestines of man and animals (intestinal myiasis).
Life History -- Adult flies often take refuge in warm
rooms and stables during winter. In mild climates, this species may
overwinter as larvae, prepupae, or pupae. During severe winters, however,
only pupae survive. Overwintering adults often become active by late
February, but emergence of new flies from overwintering pupae usually
does not occur before mid-March.
Two to 5 days after emerging, female flies begin depositing
eggs on the surface of moist, decaying substrates. Eggs incubate only
1.5 to 2 days before larvae hatch. These maggots feed and develop for
7 to 10 days. Within 9 to 14 days, a new generation of flies emerges
and the life cycle is repeated. Though detailed outdoor studies have
not been carried out, results of lab experiments suggest that as many
as seven successive generations occur each year.
Adults of this genus may live as long as two months.
Populations flourish during cool seasons, particularly spring, early
summer, and late fall. Peak numbers usually occur by July after which
dry, hot weather and parasitism causes populations to subside until
fall. Lesser house fly maggots are often common in poultry and livestock
see the page on the
treatment is the same in houses. Treatment in poultry situations would
need to be carried out by a qualified pest controller.
poultry houses, the use of mists, fogs or baits may be necessary for
fly control. Insecticides should not be applied to the manure for maggot
control. Manure should be kept dry and removed only during the winter.