"Sand flies" in South Florida are no-see-ums (Culicoides biting midges) — 1–3 mm long, penetrate standard window screens, bite at dusk and dawn, and their bite is disproportionately painful. They breed in Intracoastal tidal marsh and are worst in coastal communities. Professional barrier spray is effective against no-see-ums and mosquitoes in the same treatment.
Sand Flies vs. No-See-Ums vs. Mosquitoes: The South Florida Reality
| Feature | True "Sand Fly" | No-See-Um (what FL calls "sand fly") | Mosquito |
|---|---|---|---|
| Common name | "Sand fly" (local/informal) | No-see-um (official common name) | Mosquito |
| Scientific family | Psychodidae (true sand flies — rare in US) | Ceratopogonidae (biting midges) | Culicidae |
| Body size | 2–3 mm | 1–3 mm | 4–12 mm |
| Visible to naked eye? | Barely | Barely | Yes |
| Screen penetration | Yes — passes standard 16-mesh screens | Yes — passes standard 16-mesh screens | No — standard screens block |
| Bite sensation | Sharp, immediate, intense for size | Sharp, immediate, intense — disproportionate for size | Often not felt at time of bite |
| Bite pattern | Multiple bites, clustered | Multiple bites in exposed areas, clustered | Scattered individual bites |
| Peak activity | Dusk and dawn, calm conditions | Dusk and dawn, winds under 5 mph | Dusk, dawn, night (species-dependent) |
| Stopped by wind? | Yes — calm conditions only | Yes — winds above 5–8 mph stop activity | Partly — some species fly in wind |
| Disease transmission | Leishmaniasis (not established in continental US) | Bluetongue (livestock), rarely human pathogens in FL | West Nile, dengue, Zika, EEE, heartworm |
| Spray treatment | Responds to barrier spray on vegetation | Responds to barrier spray on vegetation | Responds to barrier spray on vegetation |
Where No-See-Um Pressure Is Highest in South Florida
- â— Intracoastal waterfront communities — Lighthouse Point, Lauderdale-by-the-Sea, Boca Harbour, Bermuda Riviera, Bay Colony, Las Olas Isles, Harbor Beach
- â— Coastal east-of-I-95 neighborhoods in Boca Raton — Boca Harbour, Spanish River Land, Camino Gardens, Royal Palm areas near the Intracoastal
- â— Pompano Beach waterfront — particularly east of US-1 near the Intracoastal and ocean
- â— Communities adjacent to mangrove or tidal flat areas — anywhere the Intracoastal has natural or semi-natural shoreline
- â— October through March: coolest, calmest nights are the worst conditions. Summer wet season mosquito pressure often exceeds no-see-um pressure.
Ready to reclaim your yard? Free assessment — no contracts, plant-oil formula.
Frequently Asked Questions
What are "sand flies" in South Florida?
In South Florida, the insects locally called "sand flies" are almost always no-see-ums (Culicoides species, family Ceratopogonidae), also known as biting midges. True sand flies (family Psychodidae) that transmit leishmaniasis are not established in the continental United States — when South Floridians, particularly in Palm Beach and Broward Counties, say they're being attacked by sand flies, they're describing Culicoides biting midges. No-see-ums are approximately 1–3 mm in length — so small they can penetrate standard window screens and netting — and their bite is remarkably painful for their size, producing an immediate sharp sting followed by an intensely itchy welt that can last 1–2 weeks.
Why are sand flies (no-see-ums) so bad in South Florida?
South Florida has exceptional no-see-um pressure due to: (1) Tidal flat breeding habitat — Culicoides species breed in brackish coastal marsh, salt marsh, and mangrove areas along the Intracoastal Waterway and barrier islands. South Florida's extensive Intracoastal system and coastal development creates maximum coastal no-see-um pressure. (2) Year-round warm temperatures — no-see-ums can breed and be active year-round in South Florida's climate. (3) Wind-pattern concentration — no-see-ums only fly in calm conditions (under 5–8 mph winds). South Florida's frequent calm, humid evenings from October–April (especially on the coast) create ideal no-see-um activity conditions. (4) Housing density near breeding habitat — coastal communities in Boca Raton, Fort Lauderdale, Deerfield Beach, and Lighthouse Point are immediately adjacent to Intracoastal no-see-um breeding areas with short dispersal distances to residential properties.
What time do sand flies (no-see-ums) bite?
No-see-ums are most active at dusk and dawn — the 30 minutes before and after sunset, and the 30 minutes around sunrise. They do not fly in winds above 5–8 mph, so calm evenings produce the worst activity. In South Florida: (1) October through March is historically the most problematic no-see-um period — cooler, calmer evenings create ideal conditions. (2) June through September (wet season) produces worst mosquito pressure but variable no-see-um pressure — afternoon sea breeze often reduces evening calm conditions that no-see-ums require. (3) Coastal communities (Lauderdale-by-the-Sea, Boca Raton east of I-95, Lighthouse Point, Deerfield Beach oceanside) experience more no-see-um pressure than inland communities due to proximity to Intracoastal tidal breeding areas.
Do regular screens keep out sand flies (no-see-ums)?
Standard window and door screens (16-mesh) do not stop no-see-ums. Their 1–3 mm body size allows them to pass through standard residential screens — which is why you can get bitten indoors near screened openings during peak activity times. Solutions: (1) No-see-um screens — 20×20 mesh or finer screen fabric blocks no-see-ums. These can replace standard screen in screen rooms, lanais, and windows most affected. Drawback: significantly reduces airflow. (2) Stay indoors during peak windows — 30 minutes before to 30 minutes after sunset on calm evenings. (3) Use a fan — air movement above 5–8 mph prevents no-see-ums from flying or landing. A box fan on low creates enough air movement to stop no-see-um activity near seating areas. (4) Barrier spray — treating the vegetation surrounding your outdoor area kills resting no-see-ums on contact and reduces population pressure at the source.
Does mosquito spray also work on sand flies (no-see-ums)?
Yes — professional barrier spray applied to your vegetation is effective against no-see-ums. No-see-ums, like mosquitoes, rest in vegetation during the day and between biting bouts. Treating this vegetation with a professional formulation kills resting insects on contact and creates a residual that intercepts them as they attempt to rest or move through. At Mosquito Shield, our MPB natural plant oil formula is effective against both mosquitoes and no-see-ums in the same treatment application. In South Florida, particularly in coastal communities with heavy Intracoastal tidal breeding pressure, treating for both simultaneously is the most efficient approach — and the reason many of our coastal clients notice improvement in both mosquito and no-see-um activity after the first few treatment visits.
Stop No-See-Ums and Mosquitoes Together
One barrier spray application addresses both mosquitoes and no-see-ums in the same vegetation treatment. Most effective for coastal South Florida communities near the Intracoastal. FL License JB313837. No contracts.
After nearly two decades in corporate finance — including managing a $1B+ P&L at Chico's FAS — Eric Vincent earned his MBA from Rollins College and made a deliberate pivot into pest control, completing his Pest Control Technology degree at the University of Florida while building Mosquito Shield of Boca and Fort Lauderdale from the ground up. He holds five Florida state licenses including Certified Pest Control Operator (JF341961) and Public Health licensee (PH340549), and is currently partnered with Arkion Life Sciences on next-generation all-natural mosquito control research.