Black flies are part of the natural environment. They also may be one of the most annoying and serious pests affecting the Northwest Territories. Black fly activity occurs a few weeks after the ice leaves streams and rivers in the spring and continues until the first frost in the fall.
Tourism & Parks
Black Flies
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| Black Flies- An Introduction: | |||||
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Black flies are active during daylight hours in sheltered areas, particularly during cloudy periods. In open areas, black flies are active in the early morning and in the evening shortly after sunset, which is considered the peak time for black fly activity. Additionally, black fly activity increases at the approach of storms, however, rain and cold inhibit activity. Black fly swarms may be massive or vicious. Alternatively, black flies can occur in such small numbers, they are barely noticeable. As black flies bite quietly and painlessly, you may not be aware of the bite until you notice a small reddish bump on your skin. Black flies bites can occur behind your ears, around your neck and belt line and on the lower parts of your legs and arms. Scratching a bite should be avoided as it can cause skin infections. Toxins injected during a severe black fly bite can result in headaches, nausea, fever and swollen glands. The transmission of disease or parasites by black flies is unknown in Canada. |
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| Life Cycle of Black Flies: | Black flies have four stages of growth: egg, larvae, pupae and adult. The first three stages require fast moving water. Females lay single layer clusters of yellowish to black eggs on the surface of rocks , sticks or vegetation located below water level in swift moving streams and rivers. The larvae hatch from the eggs within a few days or months, depending on the species. They attach themselves to rocks or vegetation in the swiftest portion of the water and feed by filtering microscopic particles from the water. When fully mature, larvae measure about 6mm long and are grey or brown in colour and are ready to pupate. The larvae spin a vase-like cocoon and pass into the pupae stage that lasts only a few days. The adult emerges quickly and flies off in the search of food. The females of the biting species require blood meals before they can produce mature eggs. The males and females of the non- biting species, feed on nectar and plant juices. Black flies, over winter, in either the egg or larval stage below the water surface and resume development after spring break- up. There are at least two generations of black flies a year. |
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| Black Fly Environment: |
Remember black flies occur in the early morning to late afternoon and before storms. Try to reduce activity in infested areas during these times. Buildings, tents and enclosed shelters are safe havens from black flies. |
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| Natural Predators: | Black flies have natural predators, which include insectivores (ie. swallows) and other insects (ie. dragonflies) to help reduce the number of black flies. Natural predators can be attracted with feeders to areas with large numbers of Black Flies. |
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