No-see-ums, also known as biting midges or sand flies, are a common nuisance for anyone spending time outdoors in Florida. These tiny insects, primarily species from the genus Culicoides, are barely visible, measuring less than three millimeters in length. Despite their small size, they deliver a painful bite that often leaves itchy, red welts on the skin. Female midges require a blood meal to produce eggs, which is why they seek out humans and other warm-blooded animals.
Understanding No-See-Um Activity in Florida
The question of a “no-see-um season” in Florida is complicated by the state’s mild, subtropical climate. Biting midges are present year-round, especially in southern regions where temperatures rarely drop significantly. However, their activity dramatically increases during specific periods, leading to a noticeable surge in population known as the peak season.
The primary peak season for intense swarming typically runs from late spring through early fall, roughly between March and October. Large numbers begin to appear as soon as the spring warming trend begins and remain abundant throughout the summer. Activity can also peak in the fall, particularly in October and November, following periods of high tide that facilitate mass hatching in coastal areas.
Geographic location strongly influences the intensity and timing of activity. Coastal zones, salt marshes, and mangrove areas provide ideal brackish, muddy breeding grounds, resulting in higher populations than in many inland areas. The combination of warmer temperatures and high humidity during the peak months creates an environment perfect for mass reproduction and swarming.
Key Environmental Factors Dictating Swarms
The surge in no-see-um swarms is directly tied to specific environmental mechanisms. Temperature plays a primary role, as the insects are warm-weather species whose activity significantly slows or ceases entirely when temperatures fall below approximately 60°F. The consistently warm, humid weather allows for continuous development through their life stages.
Moisture is another necessary element, as no-see-ums lay their eggs in moist soil, mud, or decaying organic matter. Coastal swarms are often connected to tidal cycles, where high tides flood the salt marsh, allowing eggs to hatch in large numbers. Dry spells can also lead to outbreaks in coastal areas because lower water levels concentrate salt in tidal flats, creating a hyper-saline environment highly efficient for reproduction.
A major factor enabling midges to bite is the absence of wind, as they are weak fliers. They are most active during calm periods, typically around dawn and dusk. A breeze as gentle as a ceiling fan is often enough to disrupt their flight path, which is why swarming is less common during windy parts of the day.
Protecting Yourself From Biting Midges
Personal protection against biting midges requires a multi-pronged approach focused on physical barriers and repellents. Since no-see-ums are most aggressive during the calmer hours of dawn and dusk, avoiding outdoor activity during these times can significantly reduce exposure. Wearing long sleeves and long pants minimizes exposed skin. For chemical protection, insect repellents containing DEET or Picaridin are recommended, as is Oil of lemon eucalyptus. Applying a fan to an outdoor sitting area is an effective non-chemical solution, as the midges cannot fly against even a slight breeze.
To keep them from entering a home, standard window and patio screens are often ineffective due to the midge’s tiny size. Homeowners should install specialized fine mesh screening, often referred to as “no-see-um mesh,” which has a much tighter weave, such as a 30×30 configuration, to physically block entry. Additionally, eliminating areas of moist soil or standing water near the home, such as in overwatered landscaping or gutters, removes potential breeding sites.