Black Flies

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Black Flies

Each spring we see lesions such as those pictured on the right. Often the clients are concerned that it is ringworm because of the circular shaped spots. Actually a fungus infection such as ringworm rarely looks anything like this. Black Fly bites occur almost entirely on longer legged dogs. That is because their favorite places to bite are the thin haired, thin skinned under belly area, groins and armpits. They swoop in under the dog for a quick blood meal. A dog will suffer multiple bites in a short time. The client will report the lesions appeared very quickly. A few are seen one day and even more each day the dog is outside.

The Black Flies of southern Michigan are of a very small type thus they go undetected. The male Black Fly feeds mostly on plant nectar. It is the female that feeds on blood in preparation for laying her eggs. She finds some running water such as a creek or river and deposits her eggs into the water. The larvae hatch out and then hold onto an object while they feed. They have small fans around their mouth which collect organic matter, bacteria and algae for food. The larvae form a pupae (cocoon) and emerge as an adult fly. Actually the presence of Black Flies indicates a healthy or improving ecosystem. Polluted water inhibits their lifecycle.

Usually no treatment is needed since the dog often seems unaffected. If the owner feels treatment is needed they may use a topical cortisone cream when only a few bites are present. Many bites are better treated using oral Benedryl since such a large area would be difficult to cover with a cream. In severe cases such as pictured on this page an injection of cortisone may be given by the veterinarian.

Any insect repellent you would use on a toddler is appropriate to use on the body areas preferred by the Black Flies. If it is possible the dog may also be kept away from areas of running water. Also don't forget the little children. Certainly the flies will find their soft skin especially tasty.

Close up of a Black Fly. Also called a No-See-Um because they are actually less than 1/4 inch in size.

These numerous bites occurred over 2 days. Longer legged dogs such as this Great Dane are more susceptible as the flies have more room to fly under and bite.

Armpit bites on the same dog. The flies prefer the hairless, thin skin areas to bite.