Stay in the know about wildlife, water quality, and ecosystems on Sanibel and Captiva Islands and in Southwest Florida

Why Are There So Many No-See-Ums on Sanibel?

March 7, 2024
Brackish Habitat In BHP Crop 1600

You may have noticed that there seem to be more occurrences of “no-see-ums” or biting midges on the island these days. This is a result of the storm surge from Hurricane Ian that inundated Sanibel’s vast freshwater bodies with pure saltwater converting them to brackish water bodies, as well as increasing the salinity in mildly brackish areas.

No-see-ums are a type of fly of the order Diptera, in the family Ceratopogonidae that are found throughout the world representing almost 4,000 species. In Southwest Florida, there are multiple species in the genus Culicoides that begin as an egg, hatch into a larva, and change into an adult fly. The adult is barely visible at 1/8 inch, hence its name.

No-see-um before and after a bite that fills its abdomen with blood. Photos by Constance Darrisaw

Their increased presence has occurred on islands as far south as Marco Island. No-see-ums breed in salt marshes and other highly brackish water bodies.

As wetlands become more fresh with subsequent rainy seasons, reduced quantities of no-see-ums should be evident.

SCCF Wildlife & Habitat Management Director Chris Lechowicz

“With Sanibel’s water bodies mostly being considered brackish these days, biting midges have much more habitat in which to propagate which is being felt by both residents and visitors,” said Lechowicz.

To minimize exposure, be sure to cover up well during peak activity times for no-see-ums, including dusk and dawn, when the wind is minimal, as well as cloudy days.

Although most people do feel the irritating bite of these biting midges that goes away quickly, others have much longer experiences with irritation and itching. Some people refer to them as sand flies, which is incorrect. Sand flies are of the family Tabanidae of flies, including horse flies.

Peak no-see-um breeding time in southwest Florida is March and April. This is when, in a non-El Niño year, water levels are low and higher concentrations of salt make optimal conditions for reproduction.

With increased rainfall, the salinity of many of Sanibel’s wetlands will decrease over time, especially those connected to the Sanibel River due to weir releases during high water.


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