BITING FLIES (Mosquito & Black Fly)

MEET THE PEST

Some of the more common biting flies in the Atlantic provinces include deer flies (stouts), sand flies (no-see-ums), black flies and mosquitos. Most people have likely experienced one or more of these pests. Biting flies are most active at sunset and sunrise, when winds are low, temperatures are warm and humidity is high.

Deer flies are 2 inch (1 1/4 cm) long. Their plump bodies are brown, black and orange. Their wings may be clear or banded. Deer fly bites can be very painful. They usually attack a person on the arms, head or neck. Deer flies are very common in woody or marshy areas, particularly on warm summer days.

Sand flies are much smaller, 1/10 inch (2 2 mm). Thus, they are commonly referred to as no-see-ums. Their bodies are hairy and sometimes spotted. Because they are so small and fly quietly, their presence is not suspected until they bite. This bite can be quite painful.

Mosquitos are 1/4 to 2/5 of an inch (4-10 mm) long. They are long-legged insects that have a long, sharp mouthpiece used to puncture skin and suck blood. Mosquitos have delicate wings and can easily be heard when hovering around a host preparing for a blood meal. They are more active at dusk or at night in swampy and woody areas.

Black flies are 1/8 to 1/5 of an inch (2-5 mm) long. They are plump-bodied with short, cutting mouth parts used to slice the skin and create blood pools from which they feed. Bites may be most numerous on the underside and ears of animals. On humans, bites are common around the hairline, the neck, behind the ears and around the ankles.

Bites from biting flies cause irritation and discomfort, and are a threat for the spread of certain diseases. Only the female flies bite humans and other mammals to gather a blood meal which is necessary for egg development. Not only are the bites irritating, they may cause severe reactions in people who have developed allergies to them.

Control measures are available for mosquitos and black flies; however, there are no practical control measures available for deer flies or sand flies. This information sheet provides further information on mosquitos and black flies.

LIFE CYCLE

While mosquitos require stagnant water to breed, black flies need fresh running water. Stagnant water sources can be found in buckets, tires, pools, marshes or containers left around a property. Mosquitos and black flies have four stages of development - egg, larva, pupa and adult. The first three stages occur in water with the amount of time for each stage depending on water temperature and food availability. After emergence, the adults mate and the female seeks out a blood source before laying its eggs. Up to 100 eggs are laid, either in water, on grass or other vegetation or in soil close to the water source. When water is present, eggs hatch into the larval stage (two to three days), although some species produce eggs which overwinter. Larvae are worm-like organisms which constantly wriggle around in the water. Larvae undergo four development stages (two days to two months, depending on the species; some species may even overwinter as larvae) before entering the pupal stage. The older larvae move close to the shore to spin a cocoon and develop into the inactive pupal stage which lasts up to ten days. Adults then emerge from the pupae, mate, find a blood meal and lay eggs. Adults also get nourishment from flower nectar. Biting fly adults tend to gather in large groups and have high reproduction rates.

CONTROL

Monitoring

If large numbers of biting flies are present, look around the area to locate breeding sites and decide what control measures are necessary. To decrease populations of biting flies, remove objects which collect rainfall. Do not allow water to remain for longer than one or two days in drainage ditches and open objects (old tires, buckets, swimming pools, etc.). Cover potholes and improve drainage.

Physical

Mosquitos are known to be attracted to dark clothing, carbon dioxide, scents or perfumes, and body odours when seeking a host for a blood meal. To protect yourself from bites, wear protective clothing such as long sleeved shirts, pants, socks and hats to limit the amount of exposed skin.

To decrease populations found around the home, remove breeding areas, install screens on windows and doors to prevent entry and reduce the amount of lighting around your property (biting flies are attracted to light).

Biological

Birds, bats, spiders and fish are just some of the natural enemies which feed on biting flies.

Chemical

Registered products such as repellents may offer short-term relief from biting flies. There are several biting fly repellents available for personal protection. Take care when applying them to young children and infants.

Always use a registered domestic class pest control product labelled for biting fly control and carefully follow the label directions.Some communities adopt biting fly control programs. These programs make use of a strain of Bt (Bacillus thuringiensis), a highly selective bacterium which acts as a stomach poison when consumed by larvae of black flies and mosquitos. This method of control is relatively environmentally friendly. If you are interested in pursuing a biting fly control program for your community or area, contact the Department of Environment or Agriculture in your region.