November 2002 Biting Midges of Coastal Florida Coastal area residents and visitors in Florida often know that something is biting, but when they look for the offender, nothing can be seen, or only an apparent speck on the skin. Florida is not only home to abundant mosquito populations, but also to minute biting insects known as “sandflies”, “no-see-ums”, “punkies” or more accurately as “biting midges”. These biting insects are most troublesome in coastal areas where most of Florida’s human population lives. These extremely small insects, less than an 1/8” long, utilize mangrove swamps and salt marshes to lay their eggs and develop in. There are 47 species of this genus, Culicoides, in Florida, only 7 are significant pests to man. In the South Walton area, 2 species are present, the most significant pest specie being Culicoides mississippiensis. It takes 5 days for this fly’s eggs to hatch at 80°F, longer at lower temperatures. Eggs, which cannot survive drying, are laid on wet mud in the salt marsh and coastal swamps. Larva must stay in areas of abundant moisture, primarily wet mud. Living in the mud, they feed on other small organisms. The total time spent in the larval stage depends greatly on the temperature and, therefore, on the season. Culicoides mississippiensis have 2 generations per year, from late September through December and again from March through May.
Like mosquitoes, only the female midge bites and takes blood. When biting, the midge uses small cutting teeth on its proboscis to make a small cut in the skin. A chemical in her saliva prevents clotting. Capillaries severed by the cut bled and form a tiny pool of blood, which is then sucked up with the proboscis. Feeding takes 2 to 5 minutes with greatest biting activity occurring at dusk and dawn or even during the daytime if winds are calm and skies are heavily overcast. Blood, like for mosquitoes, provides a source of protein for egg production. Culicoides mississippiensis can produce from 25 – 50 eggs per bloodmeal, depending upon the size of the female and how much blood she takes.
The general method of control for biting midges is the application of aerosolized insecticides to kill the adult flies. Control of biting midges is very difficult and in most instances, ineffective. This insect cannot be controlled in the larval stage because it lives in the mud. In order to kill the larva you would have to treat the substrate (mud) of the marshlands. Such a treatment would kill or impact most of the non-target organisms in the marsh. Because of this, there are no products labeled for this kind of treatment. Adulticiding, the spraying of aerosolized insecticides, is allowed and will kill actively flying adults, the problem is that there is a spray window of only about an hour or so, at dawn and dusk to spray and get an effective kill. Because spraying for adults has no effect on the larva, the adults continue to emerge from the salt marshes and migrate back into the areas that were previously sprayed. Within hours the adults are back at full strength. The result, adult control of biting midges is temporary at best.
These flies are weak fliers, strong fans are one way of keeping them from ruining an evening or morning on the patio. Repellents with DEET, from my experience, are not really effective. I’ve used them and biting midges don’t seem to be repelled but get stuck in the oily film, which renders them incapable of biting. Removal trapping, the utilization of a sophisticated system of suction traps baited with CO2, has been shown to provide significant relief when setup around a resort or hotel area, but the cost is prohibitive for the average homeowner.
The best way to protect against biting midges is to cover up, with clothing, all exposed areas and use a head net if you choose to be out when these insects are active. Another strategy is to avoid their periods of peak activity, dawn and dusk. Otherwise, these seemingly invisible insects will drive you crazy with their biting. |