How to Keep No-See-Ums Out of Your House

No-see-ums are tiny biting midges, also called biting gnats or sand flies. They are about the size of a pinhead, and their bites itch for days. In Florida they breed in salt marshes, mangroves and other wet ground, so homes near the coast, the bays and ponds see the most of them. They are most active around dawn and dusk, and on calm, humid days.

Standard window screen mesh is usually woven at 18 by 16 strands per inch. The openings are small enough to stop mosquitoes and flies, and large enough for many no-see-ums to get through. Gaps make it worse:

• Holes and tears in the mesh
• Mesh pulled loose from the frame along one edge
• Bent frames or split corners that leave a gap at the window
• Window screens that do not fit the window, or are missing
• A sliding screen door that is off its track, the wrong size, or does not close flush against the frame

No-see-um mesh is woven tighter, usually 20 by 20 strands per inch, with openings too small for most no-see-ums to get through. It looks much like standard mesh. The trade-off is a little less airflow and a slightly darker view, because the weave is denser.

You do not need it on every window. It makes the most sense on the windows and sliding screen doors that face the water, and the ones you keep open in the evening. The rest can keep standard mesh.

Switching is a window rescreening job: the frame you have stays, and the no-see-um mesh goes in.

No-see-um mesh only works if the screen fits. A tight weave in a bent frame, or in a sliding screen door that sits off its track, still leaves a way in. On window screens the usual causes are bent frames, split corners, loose spline, and missing clips or tension springs. On sliding screen doors they are worn rollers, a damaged track or a door that is the wrong size. Each of these is a repair, and it is worth doing at the same visit as the new mesh.

Window screens do most of the work, and two habits help:

• Keep windows and doors closed around dawn and dusk, when no-see-ums are most active
• Run a fan near open windows and doors. No-see-ums are weak fliers, and moving air keeps many of them away

Call us if:

• You are getting bitten indoors with the windows open
• Your window screens are torn, loose or do not fit
• You live near the water and want no-see-um mesh on some or all of your windows
• Your sliding screen door leaves gaps or keeps coming off its track