Sunday, August 29, 2010

Are Flies Biting You Outside?

Have you ever wandered what types of flies can bite you outside, besides a female mosquito? Well there are plenty of other biting flies, including deer flies, horse flies, stable flies, black flies, biting midges and sand flies. All biting flies locate humans and other animals by sensing things in the environment, such the carbon dioxide, dark colors, movement, warmth and perspiration. Once a host is located, a biting fly inserts its piercing mouthparts and injects its saliva with anticoagulants to keep the blood flowing. In sensitive individuals, the fly’s saliva can cause life-threatening allergic reactions. In addition, some flies can transmit disease.
Deer flies are about ¼-inches in length and are typically yellow-brown to black in color with dark bands on their wings. The larvae of deer flies are aquatic so the adult flies are usually found around streams, lakes, ponds, marshes and swamps. The adult flies have scissor-like mouthparts that cut into skin, causing blood flow which they lap up. Deer flies (Chrysops discalis) can transmit tularemia, which is a bacterial disease.
Horse flies are over 1 inch in length and black in color or light brown with shiny green eyes. They are strong, fast fliers and use their scissor-like mouthparts to cut into skin. The larvae of horse flies usually live in water or in moist locations where they prey on other insects. As the larvae grow and then pupate, they move to dryer soils.
The stable fly is ¼-inches in length, and gray in color with four dark stripes on its thorax. This fly has pointed mouthparts that it uses to suck blood, causing a sharp pain when it bites. Stable flies lay their eggs in piles of decaying vegetable matter, such as haystacks, grass clippings and manure.
Black flies are around ⅛ inches in length with broad wings and a hump-backed appearance. They prefer wet environments so they are found near ponds, creeks and rivers. Even though black flies do not transmit disease to humans in the U.S, they can threaten the lives of livestock and humans from inhalation of large swarms or by allergic reactions and blood loss from many bites.
Biting midges, also called “punkies,” and “no-see-ums,” are around 1/32 inches in length. Due to their small size, they can sometimes fly through window and door screens. The larvae of biting midges live in moist sand or soil, decaying vegetation, tree holes and near ponds, rivers, creeks or marshes so the adult flies can be pests around these waterways.
Sand flies are around ⅛ inches in length, hairy and brown to gray in color, with wings that form a “v” when at rest. The sand fly larvae live in moist, decaying vegetation, moss, mud or in water. Most feed on the blood of mammals, reptiles and amphibians. In many parts of the world, including south Texas, certain sand fly species are suspected of transmitting cutaneous leischmaniasis to humans, which is a disfiguring protozoan disease.

Ways to Prevent Bites
Repellents such as those containing DEET (N,N-diethyl-meta-toluamide) or picaridin are suggested to prevent most flies from bitings. Also avoiding wet areas inhabited by the biting flies and wearing light-colored long-sleeve shirts, long pants and hats will prevent some flies from biting.

Controlling Biting Flies:

Some Non-Chemical Controls:
Biting flies can be difficult to control due to all the moist habitats where the larvae can develop. However sanitation is always important, so all potential sites for larval development should be eliminated and decaying vegetation should be disposed of. Also, screens should be installed and maintained on windows and doors and finer mesh should be installed to keep out tiny biting flies, where these flies are a problem. Fans can also be used indoors and outdoors to keep areas free of flies, especially smaller flies that can not fly into the air currents.

Some Chemical Controls:

Ultra-low volume (ULV) treatments and sprays of non-residual pesticides can be used where flies are clustered in a small area. Residual pesticides can be used to spray surfaces where flies are resting, such as in vegetation and along the exterior walls of structures. Also applications of Bacillus thuringiensis israelensis (Bti) or insect growth regulators, such as methoprene, have been used to control some fly larvae.

A deer fly, Chrysops sp. (Diptera: Tabanidae), adult female. Photo by Bart Drees, Professor and Extension Entomologist, Texas A&M University.

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