Standard window screens do NOT stop no-see-ums. They are 1–3mm and pass through 16-mesh standard screen openings. If you have a screened lanai and are still getting bitten, no-see-ums are the likely cause. Fine-mesh (20–32 mesh) biting midge screens and DEET repellent are the most effective protections.
No-See-Um Activity — When They're Worst
Why South Florida No-See-Ums Are Worse Than Anywhere Else in the U.S.
Most no-see-um complaints in the U.S. come from coastal areas — but South Florida compounds every factor:
Culicoides furens — the species responsible for most South Florida no-see-um bites — breeds in the wet, organic-rich mud at the base of mangrove forests and coastal saltmarshes. Broward and Palm Beach counties have extensive Intracoastal, bay, and tidal creek edges that provide miles of ideal breeding habitat within close range of residential neighborhoods.
Unlike the Carolinas or Georgia — also known for no-see-ums — South Florida has no cold winter to reset populations. Culicoides can reproduce year-round in South Florida mud, meaning populations build continuously without seasonal die-off.
No-see-ums are too small (1mm) to fly against even a light breeze. But on calm evenings — especially after rain stalls the afternoon sea breeze — they travel inland from coastal source areas. Communities within a few miles of the Intracoastal regularly see no-see-um activity that started at the mangrove fringe.
Standard pool cage and window screens (18×16 mesh) have openings large enough for no-see-ums to pass through. They're smaller than most bugs residents expect screens to block. This is why patio and pool cage complaints are so common in East Boca, Fort Lauderdale Beach, and Lauderdale-by-the-Sea.
What Actually Reduces No-See-Um Pressure (Honest Expectations)
No-see-um control is more limited than mosquito control because the source (coastal breeding habitat) can't be treated from a residential property. Here's what each approach realistically does:
| Method | Realistic Effect | Limitation |
|---|---|---|
| Professional barrier spray (yard vegetation) | Reduces resting no-see-ums sheltering in ornamental plantings on your property | Cannot treat the coastal breeding source |
| No-see-um screens (60×60 or 80×80 mesh) | Blocks most no-see-ums from entering enclosed spaces | Significantly reduces airflow; may need fan to compensate |
| DEET or picaridin repellent | Good personal protection during peak dawn/dusk windows | Must be reapplied; not practical for extended outdoor time |
| Fans on patio/pool cage | Disrupts their flight; they cannot fly in winds above ~3 mph | Only works in enclosed or sheltered areas |
| Citronella candles | Minimal. No-see-ums are less deterred by citronella than mosquitoes | Requires calm air anyway, when no-see-ums are worst |
| County aerial spraying | Temporary knockdown of adult populations near source areas | Infrequent, not targeted to your property |
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Frequently Asked Questions
What exactly is a no-see-um and why can't you see them?
No-see-ums are biting midges in the genus Culicoides — tiny flies that are the most frequently complained-about biting pest in coastal South Florida. Here's why they're nearly invisible: SIZE: Adult no-see-ums are 1–3mm in body length — smaller than the diameter of a pencil point. At the distance you'd normally notice an insect on your skin (8–12 inches), a 1.5mm no-see-um is at or below the human visual resolution threshold under normal lighting. They are particularly invisible in low-light dawn and dusk conditions, which is exactly when they're most active. WINDOW SCREENS: Standard residential window screens are 16 mesh to the inch (the wires are 1/16 inch apart). No-see-ums at 1–1.5mm body width easily pass through 16-mesh standard screens. They can enter any window, door, or patio screen opening in a standard home. 'Biting midge screen' (also called no-see-um screen) is available at 20–32 mesh, which significantly reduces but does not completely stop no-see-um entry. The trade-off is substantially reduced airflow. SYMPTOMS BEFORE SIGHT: Most people don't see the no-see-um while it's biting — they feel the bite first (a sharp pinprick sensation), then see a small red welt appear. Unlike mosquito bites which cause immediate mild itch, no-see-um bites often cause a severe itch response that intensifies over hours and can last 24–72 hours in sensitive individuals. This prolonged, intense itch response is a hallmark of no-see-um bites and distinguishes them from mosquito bites in South Florida residents who have learned to identify the difference. NO-SEE-UM VS. MOSQUITO BITE: Mosquito bite: immediate mild itch, resolves in a few hours to 24 hours in most people. No-see-um bite: delayed intense itch starting 30–60 minutes after the bite, peaks at 12–24 hours, can persist 48–72 hours, often with visible wheal (raised area) persisting longer than a mosquito bite.
Where do no-see-ums breed in South Florida?
No-see-um larvae develop in specific habitat types that are most abundant in coastal South Florida — which explains why biting midge complaints are much higher in coastal communities (Lauderdale-by-the-Sea, Pompano Beach coastal areas, Fort Lauderdale beach neighborhoods, Boca Raton coastal areas) than in inland communities like Coral Springs or Tamarac. PRIMARY BREEDING HABITATS: (1) SALTMARSH AND MANGROVE EDGES: The saltmarsh and mangrove ecosystems that border South Florida's Intracoastal Waterway and coastal areas are the highest-density Culicoides breeding habitat in the region. The organic-rich mud at mangrove root zones and in saltmarsh vegetation margins is ideal Culicoides larval habitat — it stays consistently moist, has high organic content, and is above the water line but saturated with saline to brackish water. South Florida's extensive Intracoastal Waterway mangrove edge is one of the most productive biting midge breeding zones in North America. (2) ORGANIC-RICH MOIST SOIL: Any consistently moist, organically rich soil — the margins of retention ponds, areas under heavy mulch accumulation where soil stays damp, moist areas around air conditioning drain lines where organic matter accumulates — can support Culicoides breeding. This is why no-see-ums also affect inland residential properties, though at lower density than coastal areas. (3) BEACH WRACK AND SEAWEED: Decomposing seaweed and organic wrack deposits on beaches can support opportunistic Culicoides populations. (4) WATER MANAGEMENT BERMS: The moist organic soil at the base of Broward County's water management canal berms provides no-see-um habitat in some inland areas. WHAT DOESN'T BREED THEM: No-see-ums DO NOT breed in clean standing water (flower pots, birdbaths, buckets) — that's Aedes aegypti. They DO NOT breed in drainage canals — that's Culex. Their habitat is organic-rich saturated soil, not water-surface laying.
What times of day and year are no-see-ums worst in South Florida?
No-see-um activity in South Florida follows predictable patterns tied to time of day, season, wind, and proximity to breeding habitat: TIME OF DAY: Biting midges are crepuscular — they have peak activity at dawn (30–60 minutes around sunrise) and dusk (30–90 minutes around sunset). Low-light conditions when air cools and wind typically calms are when Culicoides emergence and host-seeking peaks. Some species have secondary overnight activity in calm, warm conditions. Midday activity is low in most coastal South Florida conditions because heat and UV inhibit Culicoides. SEASON: South Florida's coastal no-see-um populations peak from late spring through early fall (April–October) when temperatures, humidity, and saltmarsh water levels are most favorable for larval development and adult survival. However, because South Florida rarely drops below temperatures that kill adult Culicoides, some populations persist year-round in protected coastal habitats. WIND: This is the most reliable predictor of no-see-um intensity on any given day. No-see-ums cannot fly in wind speeds above approximately 2–3 mph. A calm, humid evening after a warm day is the worst condition. A breezy coastal location that gets consistent afternoon sea breezes may be significantly more comfortable than a calm, sheltered backyard even though it's closer to the mangrove breeding source. NOTABLE PATTERN: Many South Florida residents notice that beautiful, calm, perfect-weather beach evenings are exactly when no-see-ums are worst — because the same calm conditions that make the weather comfortable remove the wind that suppresses no-see-um flight.
What actually helps with no-see-ums — what works and what doesn't?
No-see-um control is more limited than mosquito control because their breeding habitat (saltmarsh, mangrove mud) is generally on public or environmentally protected land that cannot be treated. Focus is on personal protection and reducing the resting population in your yard: WHAT WORKS: (1) DEET REPELLENT: Applied generously to all exposed skin, DEET-based repellents (20–30% concentration) provide effective personal protection for outdoor activities. Reapply every 2–3 hours, more frequently if sweating heavily. (2) PICARIDIN REPELLENT: Effective alternative to DEET for people who prefer a different feel; 20% picaridin provides similar protection duration. (3) PROFESSIONAL BARRIER SPRAY IN YARD VEGETATION: While you can't treat the breeding source (coastal saltmarsh), professional barrier spray targeting your yard's ornamental vegetation, hedges, and perimeter reduces the resting no-see-um population on your specific property. Culicoides rest in vegetation between activity periods — the same treatment that reduces mosquitoes meaningfully reduces no-see-ums resting in treated vegetation. Expect meaningful improvement in yard comfort, with some continued activity from coastal migrations that enter from outside the treated zone. (4) FANS: Probably the most practical in-yard protection for seated outdoor activities. An oscillating fan creating any movement above 2–3 mph at body level prevents no-see-um flight and landing. (5) FINE-MESH SCREENS: 20–32 mesh no-see-um screens significantly reduce midge entry into screened areas. Available from specialty suppliers. Trade-off is noticeably reduced airflow. WHAT DOESN'T WORK WELL: (1) Standard 16-mesh window screens — ineffective, midges pass through easily. (2) Citronella candles — attractive myth; minimal impact on no-see-ums in outdoor conditions. (3) Electric bug zappers — attract and kill moths and harmless insects but ineffective for biting midges. (4) Source elimination — no practical source elimination available for coastal saltmarsh breeding; only a government-managed habitat management program could address the primary coastal source.
Reduce No-See-Um Populations in Your Yard
Biweekly professional barrier spray reduces no-see-um resting populations in your yard's vegetation — the same treatment that cuts mosquitoes 80%+ meaningfully reduces Culicoides sheltering in ornamental plantings. Can't treat the saltmarsh source, but can reduce what's on your property. All-natural MPB formula. FL License JB313837.
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.