What are no-see-ums in Florida, and how do you keep them from biting?

They are also called sand flies or sand gnats. Adults are usually 1 to 2 millimeters long, and the average Florida species is about 0.06 inch. About 50 of the roughly 170 kinds of Culicoides midges in the United States are found in Florida. In most species, the females feed on blood, which they need to develop their eggs. The males cannot pierce skin.

Coastal pest species such as Culicoides furens develop in marshes, swamps and mangroves, and they can reach very large numbers and are a major nuisance to campers, beachgoers and anglers. Many species can fly about 2 kilometers, or 1.2 miles.

Most bite at dusk, at night or in the morning. In cold weather and in coastal areas, many bite in broad daylight. The bite stings or burns and leaves a red area. The discomfort usually lasts minutes to hours, but people who are very sensitive to the bites may itch for two to three days.

Regular window screens do not keep them out; a screen with smaller openings, called no-see-um screen, is needed. DEET is the main repellent used against them. The University of Florida's fact sheet names no human disease spread by biting midges in the United States; the two kinds it names as disease carriers in this country spread viruses of livestock and deer.

The fact sheet comes from the Florida Medical Entomology Laboratory, part of the University of Florida's Institute of Food and Agricultural Sciences. Established in 1956, it studies biting insects that spread disease. It is at 200 9th St. SE, Vero Beach, and its phone number is (772) 778-7200.

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