Heads up: Deerflies rampant

So it turns out I am not imagining – or exaggerating – when I tell people that it seems like a squadron of deerflies escorts my truck each morning and evening as I make my way down my gravel driveway.

The deerfly population in recent weeks does seem to have grown exponentially, an insect expert with the Maine Forest Service reported.

Charlene Donahue, a forest entomologist, said Tuesday she has heard about – and seen firsthand – the swarms of deerflies, or Chrysops species of the Tabanidae family, in many parts of Maine this summer.

Typically at this time of summer, a step outside into the woods might quickly draw two or three of the biting bugs, usually to the back or top of the head. Deerflies seem to be attracted to movement or dark shapes.

This year, it’s more likely to be a dozen making the attack.

“Other people are noticing that,” Donahue said, and she has a couple of theories as to why.

Maine is home to 76 species of deerfly, “and they’re all biting flies,” she said. “They stab you with their sharp mouth parts, and they lap up the blood.” The deerfly is about the size of a housefly, but has a striped body and spotted, yellowish wings.

The different species have different life cycles with some living as larvae for a year; others live in the developmental stage for two or three years. The pupal stage lasts six to 12 days, depending on the species and temperature, according to a fact bulletin produced by the Ohio State University Extension Service.

Donahue theorizes that conditions may have been especially good this spring and summer for several species to develop in large numbers.

But she puts more stock in her second theory, which supposes that something – probably weather conditions – delayed the development of some species of the flies so that several species now are reaching adulthood at the same time.

“That’s the thing that makes sense to me,” she said.

Usually, some species might reach adulthood in early June and thrive through mid-July, and then other species might mature in late June and live through the end of July. This year, a spring cold spell may have delayed the process so that several species of deerflies now are competing at the same time for that choice spot on the back of your neck.

Donahue said the differences in the species would not be distinguishable to the average person who plucks them from hair or peels them from a dog’s snout.

Like mosquitoes, only the female deerfly bites, needing a feast of blood to lay eggs. Males feed on flower nectar and other liquids. Most females get that blood fix from animals, but they are not shy about attacking people.

They lay eggs in masses on vegetation above water. After they hatch, the larvae drop and burrow into moist or wet soils, feeding on organic debris or other insects.

According to the Ohio State University fact sheet found on its Web site, the deerfly could carry diseases such as anthrax, tularemia, anaplasmosis, hog cholera, equine infectious anemia and filariasis.

Deer flies and horseflies – which hatch later in the summer and are much larger than the deerfly – “are suspected of transmitting Lyme disease,” the fact sheet notes, citing the New England Journal of Medicine. Some people suffer “severe lesions, high fever and even general disability” from deerfly bites.

Donahue said not much research has been devoted to the deerfly, and there are no easy ways to deplete their populations.

“Insect repellent doesn’t seem to work for them,” she said, but putting double-sided tape on a hat seems to work well, capturing many as they dive-bomb the head area.

But don’t be too bugged by the overabundance of deerflies. On the good news side, Donahue said anecdotal evidence suggests Maine enjoyed a relatively mild black fly season, again, probably owing to cold weather conditions in early spring.