We have met the enemy, and she is the blackfly. She is a mindless, merciless eating machine, and what she wants to eat is you. What she lacks in physical heft is more than offset by her numbers. She and her sisters — for the biters are all female — attack in ferocious, ruthless, maddening swarms. They will turn you into a bloody, itchy, swollen mess if they don’t drive you crazy first. It is not enough to meet your enemy. You must also know her. Know her, and you might stand a chance.

Blackfly Basics
A member of the insect family Simuliidae, the blackfly is a small hump-backed fly barely one eighth of an inch long. Roughly forty species live in Maine, but only a handful of them bite humans. Females seek a blood meal to nourish their developing eggs, which they lay by the hundreds in fast-moving creeks and rivers. Males are placid, feeding only on the nectar of flowering plants.

The Season of the Itch
Blackfly season is said to run from Mother’s Day to Father’s Day, but, “it depends on the species,” says Leon Tsomides, an aquatic entomologist with the Maine Bureau of Land and Water Quality. “Generally, they emerge in spring, have one generation, and are gone by July. But there is a species on the Penobscot River, and a few other places, that has multiple generations." Blackfly larvae hatch sometime after the spring thaw when river temperatures rise, phenomena that vary not only from region to region, but also from year to year.”

Four Ways Blackflies Find You
1. Your breath. Blackflies detect carbon dioxide in your exhalations. This likely explains their tendency to swarm around your head.
2. Your temperature. Blackflies are drawn to a warm body.
3. Your wardrobe. Blackflies are attracted to dark colors.
4. Your special something. “Some people seem to be more attractive to blackflies than others,” says Charlene Donahue, an entomologist with the Maine Forest Service. “There is probably some chemical involved, but we don’t know what it is.” 

My, What Big Teeth You Have!
Consider the blackfly’s mouth: It is equipped with a pair of serrated jaws 
that work like scissors to pierce and cut skin, a barbed structure called a syntrophium with which the blackfly anchors herself in the wound, and pump-like muscles to lap up the pooling blood. As the blackfly chews upon your flesh, she bathes it in her saliva, which contains an anticoagulant to keep your blood flowing and, even more insidious, an anesthetic so you don’t feel a thing. This is not for your benefit. Rather, it buys her time to finish her meal safely. You’ll feel the effects soon enough.

Symptoms and Treatment
The blackfly’s brutal butchery makes itself known within the hour. The blackfly’s saliva also happens to be an allergen, so the bite site (and there is rarely just one) itches intensely and swells much like a mosquito bite with the added attraction of a noticeable wound in the lump’s center.

Wash with soap and water to prevent infection and apply ice to reduce the swelling and numb the pain and itching. Over-the-counter topical ointments like calamine and Benadryl cream provide more lasting relief.

Defensive Measures
1. Cover up. Wear head nets and long sleeved-shirts and pants in light colors.
2. Avoid the woods on cloudy days when blackflies are more active. Bright sun and breezes seem to keep them at bay.
3. Use insect repellents. Those containing DEET work best.

Four Good Things
1. A healthy blackfly population is a sign of good water quality. Maine had few blackflies in the 1960s when its rivers were heavily polluted.
2. Maine blackflies do not carry diseases. “One of the good things about living in a cold climate is you short-circuit disease-vectoring by insects,” says Donahue.
3. Blackflies are food for creatures we like. Trout eat their larvae. Birds and bats eat the adult flies.
4. Blackflies can be monetized for a good cause. Just ask the Maine Blackfly Breeder’s Association (official greeting: May the Swarm Be With You), a Machias charity organization that raises money through the sale of gear featuring a large blackfly and the words “Blackflies: Defenders of the Wilderness.” (maineblackfly.org)