Why does this house fly keep biting me?

If a gray, house-fly-sized fly is biting you around the ankles or lower legs, it is a stable fly (Stomoxys calcitrans), not a common house fly. House flies (Musca domestica) have sponging mouthparts and cannot bite or pierce skin at all. The stable fly carries a forward-projecting bayonet-like piercing proboscis — visible from the side as a spear-like projection from the front of the head — and both sexes actively blood-feed. The bite is sharp and immediate. If a 'house fly' bites you, it is a stable fly. Full stop.

Do both male and female stable flies bite?

Yes — this is unusual and important. Both male and female stable flies blood-feed. This distinguishes them from mosquitoes (where only females bite) and many other blood-feeding insects. Both sexes require blood meals for normal physiological function. This means that on a property with a stable fly infestation, essentially every fly in the population is a biting threat. Animal Diversity Web and the University of Saskatchewan confirm both-sexes blood-feeding behavior.

How do I tell a stable fly from a house fly?

The forward-projecting bayonet proboscis is the definitive tell — it is visible when the fly is at rest, projecting clearly forward from the head like a short spear. The house fly's mouthparts are not visible as a projection. Additionally: the stable fly has a slightly broader, spotted/checkered abdomen (the house fly's is more uniformly yellowish-gray); the stable fly holds its wings slightly spread at the tips when resting; and the stable fly bites. In practice, if the gray fly is biting you, you do not need to examine the proboscis — the behavior has already confirmed the ID.

Where do stable flies breed?

In wet, decaying organic matter. The most common breeding sources on rural NH properties: accumulated livestock manure and soiled straw bedding (especially when piled and left wet), decaying grass-clipping piles, decomposing feed spills, and any wet vegetation near barns. Merck Veterinary Manual and the University of Saskatchewan both cite wet manure and soiled straw bedding as primary sources. On residential properties without livestock, large wet grass-clipping piles and accumulated garden waste in late summer are the most common breeding sites that bring stable flies into contact with people.

Are stable fly bites dangerous?

Stable fly bites are painful and cause immediate localized pain and inflammation. For most people, individual bites are unpleasant but not medically significant — wash with soap and water and apply a cold compress. Heavy exposure (many bites in a session) can cause more significant skin reactions. Anyone who develops unusual swelling, signs of infection, or a systemic reaction should contact a physician. For concerns about severe reactions, call the Northern New England Poison Center at 1-800-222-1222 (24/7, NH/ME/VT). Stable flies can mechanically transmit some animal pathogens, but disease transmission to humans in New Hampshire's agricultural context is low-risk.

Do stable flies spread disease to humans?

Mechanical disease transmission to humans in a New Hampshire context is low-risk. Stable flies are documented mechanical vectors of some animal pathogens (they can transfer trypanosomes and other agents between livestock), but significant human disease transmission from stable flies in the Northeast is not a well-documented concern. Their primary documented harm to humans is the bite itself. Consult a physician for any bite that causes an unusual reaction or shows signs of infection, and route disease-specific questions to NH DHHS or CDC for current surveillance information.

How do I get rid of stable flies around my property?

Locate and eliminate the wet organic breeding source first. Identify wet manure piles, soiled bedding, rotting grass-clipping accumulations, or decaying vegetation near your home or barn. Remove piles or spread them thin to dry — stable flies cannot develop in dry, thin-spread material. For ongoing management near livestock, implement a weekly manure and bedding removal schedule. Biting-fly traps and sticky traps reduce adult populations as a supplement. Spraying adults without addressing the source provides only temporary relief.

Are stable flies a problem in New Hampshire specifically?

Yes, particularly on rural and agricultural properties. Stable flies are cosmopolitan across the United States, with well-documented presence throughout New England, and their relevance to NH properties follows the presence of livestock, barns, and decaying organic material. Properties with horses, dairy or beef cattle, chickens, or other livestock are at highest risk. Residential properties adjacent to farmland or with substantial composting and grass-clipping accumulations can also experience stable fly biting pressure in late summer — the peak period in NH's climate.

How is the stable fly different from a deer fly or horse fly?

All three are biting flies, but they differ in size, appearance, and breeding habitat. Deer flies and horse flies (Tabanidae) are significantly larger than stable flies — horse flies can be 3/4 inch or more — and have distinctive patterned or colored eyes and large bodies. They breed in wet soil near ponds, streams, and marshy areas. The stable fly is house-fly-sized, dull gray, and breeds in manure and decaying vegetation near livestock facilities — not near water. If the biting fly is house-fly-sized and gray, it is a stable fly. If it is noticeably larger with distinctively colored eyes, it is a deer fly or horse fly.

Can pest control help with stable flies on a farm?

Yes — and the most valuable professional service is often a breeding-source assessment and management plan rather than adult insecticide application alone. A licensed technician can identify specific problem areas, help design a manure and bedding management schedule, apply targeted adulticides or larvicides where appropriate, and advise on structural improvements (drainage, covered manure storage) that reduce breeding habitat. Anchor's General Pest Control service covers stable fly management for rural residential and small agricultural properties in southern New Hampshire.

Stable fly · Stomoxys calcitrans

Flies & GnatsNH resident

Stable Flies in New Hampshire — The Biting "House Fly"

Also called Biting house fly · Barn fly · Dog fly · Beach fly

The stable fly (Stomoxys calcitrans) looks almost exactly like a house fly — same gray body, same four thoracic stripes — but it carries a forward-projecting bayonet-like piercing proboscis and both sexes actively blood-feed. If a 'house fly' is biting you around the ankles, it is a stable fly. It breeds in wet decaying vegetation, manure, and soiled bedding. The fix is drying out and removing that wet organic matter.

At a glance

Species: Stomoxys calcitrans; the 'biting house fly'; family Muscidae
Size: ~5–8 mm; house-fly-sized; Merck Veterinary Manual; Animal Diversity Web
Best tell: Forward bayonet-like proboscis — it BITES; visible from the side; Merck Veterinary Manual
Who bites: Both sexes blood-feed; Animal Diversity Web; U. of Saskatchewan
Breeds in: Wet manure, soiled straw bedding, rotting vegetation, grass clippings; Merck Veterinary Manual; U. of Saskatchewan
Peak in NH: Late summer–early fall; rural and livestock properties; cosmopolitan U.S. distribution

The short of it

If the house fly is biting you, it is a stable fly.

The stable fly (Stomoxys calcitrans, family Muscidae) is the cluster's biting fly — and the one species guaranteed to get your attention. It looks almost exactly like a common house fly: same size, same dull gray body, same four thoracic stripes. The difference is invisible until the fly lands on you, and then you feel it immediately: a sharp, stabbing bite, typically around the ankles and lower legs.

Unlike house flies with sponging mouthparts, the stable fly carries a forward-projecting bayonet-like piercing proboscis. And unlike most blood-feeding insects where only the female feeds, both male and female stable flies blood-feed — making them a persistent nuisance wherever they occur.

Their breeding medium is wet, decaying organic matter: livestock manure, soiled straw bedding, wet grass clipping piles, rotting vegetation, and even seaweed in coastal settings. This makes them a real problem for rural New Hampshire properties with barns, horses, dairy cattle, or chickens, with peak biting pressure in late summer into early fall.

Breeding-source-first applies exactly as it does to house flies: the fix is drying out and removing the wet decaying organic matter they breed in, not killing the adults you see.

Identify it

How to identify a stable fly

The forward bayonet proboscis is the only reliable tell from the house fly — and if you feel the bite, you have your confirmation. Stable flies are house-fly look-alikes in every other respect. The mouthpart is the ID, not the size.

Species profile

Stable fly

Scientific name: Stomoxys calcitrans
Family: Muscidae
Size: ~5–8 mm (house-fly-sized)
Coloration: Dull gray; four dark thoracic stripes; slightly broader, checkered/spotted abdomen compared to house fly
Habitat: Barns, feedlots, stables, and outdoor areas with wet manure, soiled bedding, rotting vegetation, grass clippings, or seaweed.
Active season: Late summer–early fall peak; warm season generally
Diet: Blood (both sexes); adults require blood meals for reproduction.
Reproduction: Females lay eggs in decaying organic matter — wet manure, soiled straw, rotting grass clippings.
Lifespan: Egg-to-adult cycle approximately 2–4 weeks; adults active warm season.

Cosmopolitan; present throughout the United States including New Hampshire; particularly relevant on rural and agricultural properties.

The tells — key ID features

Bayonet-like proboscis projecting forward from the head — the single diagnostic tell vs. the house fly; visible from the side.
Otherwise identical size and dull gray appearance to a house fly (four thoracic stripes).
Slightly broader, spotted or checkered abdomen.
Wings held slightly spread at the tips when at rest (house fly holds wings closer together).
Bites around the ankles and lower legs — the behavior is diagnostic.

Size, to scale

The insect

~5–8 mm (~1/4 in)

Compared to

House-fly-sized — the bayonet mouthpart is the giveaway, not the size

Looks bigger than it is

The forward-pointing proboscis is visible when the fly is at rest, projecting clearly from the front of the head. If you see this feature on a gray fly, it is a stable fly.

Is it actually this? — the confusion species

Common house fly

How to tell — House flies have sponging mouthparts that do not project forward and cannot bite. The stable fly's bayonet proboscis is the separator — and the bite is the ultimate confirmation. If a gray fly bites you, it is a stable fly; house flies cannot bite.

Face fly

How to tell — Face flies (Musca autumnalis) also resemble house flies and can be found near livestock, but they feed on secretions from animal faces rather than blood-biting. Stable fly is the one that actually pierces skin.

Horn fly

How to tell — Horn flies (Haematobia irritans) are considerably smaller than stable flies (~3–4 mm) and primarily feed on cattle, resting on the animal's back and sides. Stable flies are larger and bite people and livestock at the lower legs.

What you'll notice

Signs of a problem

Stable fly signs combine the biting behavior with the proximity to their wet organic breeding source. These are the signs and what each one means.

Painful daytime bites around the ankles and lower legs

What it means — Stable fly, not a house fly — the bite is the definitive identification. Stable fly bites are sharp and persistent.

Biting flies near barns, pastures, or piles of wet grass clippings or straw

What it means — The breeding source is nearby — wet decaying organic matter within the immediate area is sustaining the population.

Livestock stamping feet, bunching together, or showing reduced productivity

What it means — Heavy stable fly pressure on the animals; a significant infestation affecting livestock health and production.

Flies resting on fence posts or vegetation near the barn in the morning or evening

What it means — Stable flies rest on structures when not actively feeding; their presence in numbers near livestock areas confirms an active infestation.

How much it matters

The real risks, calibrated

The stable fly's defining risk is its bite — painful, persistent, and sustained by an active breeding population in wet organic material.

Overall risk

Moderate

Painful bites to people and livestock

Moderate

Onset: Immediately upon contact

Stable fly bites are sharp and cause immediate pain, typically at the lower legs and ankles. Both sexes blood-feed. Bites can cause localized inflammation and, in sensitive individuals, more significant reactions. If a bite causes a significant reaction, contact a physician; for severe reactions, call NNEPC 1-800-222-1222.

Livestock economic losses

High

Onset: During peak season

Stable flies cause significant cattle and livestock production losses through reduced weight gain and milk production. Peer-reviewed estimates place annual U.S. cattle-production losses in the high hundreds of millions to over a billion dollars depending on the study (various peer-reviewed sources).

Mechanical pathogen vectoring

Low risk

Onset: Uncommon in our region

Stable flies are mechanical vectors of some animal pathogens; disease transmission to humans is low-risk in New Hampshire's context.

What you can do

DIY — what works, what backfires

Stable fly control centers on the breeding source: wet, decaying organic matter. Remove or dry it out, and the fly population declines. Killing adults you see without addressing the source is temporary at best.

What actually works

Remove or spread wet manure, soiled straw bedding, and rotting-vegetation piles — these are the primary stable fly breeding sources; spreading thin allows drying and destroys the breeding habitat.
Keep livestock bedding dry — stable flies cannot successfully breed in dry bedding; regular removal and replacement of wet straw and manure prevents buildup.
Remove or compost grass-clipping piles promptly — wet clipping piles near the house or barn are a commonly overlooked stable fly source.
Use sticky fly traps or commercial biting-fly traps near livestock areas to reduce adult populations.
Drain or fill low-lying wet areas near barns and pastures that accumulate decaying vegetation.

What backfires

Don't treat a biting stable fly as a harmless house fly — they are not the same insect; the stable fly requires a different response and should prompt you to locate and address the wet breeding source.
Don't spray adult stable flies as the primary control while wet breeding piles remain — new adults will emerge from the source faster than you kill them.
Don't pile and leave grass clippings near living areas or near animal housing — a large moist clipping pile is a productive stable fly nursery.
If a stable fly bite causes an unusual reaction, do not ignore it — wash the bite, monitor for swelling or signs of infection, and contact a physician if symptoms concern you. For severe reactions, call the Northern New England Poison Center at 1-800-222-1222.

Local Context

Stable flies in New Hampshire

Stable flies are present on rural and agricultural properties across New Hampshire — dairy and horse farms, properties with livestock, and residential properties near barns or with decaying vegetation piles. NH presence is asserted from their cosmopolitan U.S. distribution and well-documented New England livestock relevance; they are common in agricultural settings throughout the Northeast. Peak biting pressure in NH typically occurs in late summer into early fall — August through September. Residential properties adjacent to farmland or with substantial composting and organic material piles can also experience stable fly pressure in late summer.

Peak season

Late summer to early fall; peak biting pressure August–September on rural/livestock properties

You might actually have

Common house fly (sponging mouthparts, does NOT bite — the primary ID contrast)
Deer flies and horse flies (also biting; larger; different breeding medium)

We serve these communities

ManchesterConcordDerryBedfordAmherstGoffstownLoudonBristol

Hillsborough · Rockingham · Merrimack Counties

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Same-day service
Family-owned since 2017

Service Area Map

Southern New Hampshire

When it's past DIY

When to call a pro for stable flies

Barn, feedlot, and rural-property stable fly infestations often require systematic breeding-source management beyond what an individual homeowner can address alone. A licensed technician can assess breeding conditions and implement a management plan.

Signals it's past DIY

When to call a pro

A persistent biting fly problem on a rural property or near livestock despite your own source-management efforts.
Heavy infestation pressure affecting livestock health or productivity.
Breeding source management on a large property or barn complex where the source is extensive or difficult to locate.
Residential properties with an adjacent farm source that is outside your control.

Keep them out — prevention

NH-specific

Manure and bedding management

Remove and spread livestock manure and soiled bedding at least weekly during the active season. Stable flies cannot develop in dry, thin-spread manure — it is the wet, piled, anaerobic condition that enables them.

Drainage and site management

Ensure good drainage around barns, feedlots, and pasture areas to prevent the accumulation of standing water and wet organic material that stable flies require for development.

Vegetation management near the home

Remove rotting vegetation, grass-clipping piles, and decaying garden waste promptly, especially in late summer when stable fly pressure peaks in NH. These materials near a residence create stable fly habitat that bites humans in addition to livestock.

Not sure it's a stable fly?

A licensed NH technician can confirm the species and tell you honestly whether it's a DIY fix or a job for a pro — free inspection, same-day service across Southern New Hampshire.

Get a Free Inspection (603) 785-0118

Common Questions

Frequently asked questions

Sources(6)

[1]
Merck Veterinary Manual — Stable Flies
proboscis description, breeding media, livestock management
industryverified 2026-06-30
[2]
Animal Diversity Web — Stomoxys calcitrans
both-sexes blood-feeding, biology, identification
academicverified 2026-06-30
[3]
University of Saskatchewan (WCVM) — Stomoxys calcitrans
breeding media, both-sexes feeding, biology
academicverified 2026-06-30
[4]
ScienceDirect — Stomoxys calcitrans (economic-loss review)
livestock economic losses (high hundreds of millions to over a billion dollars, study-dependent)
academicverified 2026-06-30
[5]
Texas A&M Insects — House Fly / Stable Fly Contrast
size comparison, house-fly vs stable-fly disambiguation
extensionverified 2026-06-30
[6]
UNH Cooperative Extension — Livestock Fly Management
NH source-first livestock fly management guidance
extensionverified 2026-06-30

Written & reviewed by

Verified

Daniel Brady

NH-Licensed Pesticide Applicator · License #782664 (NHDAMF, RSA 430)

Daniel Brady is the New Hampshire–licensed applicator behind Anchor Pest Services, a family-owned pest control company serving the Manchester area since 2017.

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Last updated 2026-06-30

New Hampshire pest control

Dealing with stable flys in your home?

Anchor Pest Services identifies and handles stable fly problems across southern and central New Hampshire. Family-owned since 2017, NH license #782664.