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Avoiding Mosquitoes

Ah, spring, the season of the blessed bloom-and maddening mosquitoes. If you don't like slathering yourself in DEET, then you'd better learn how to avoid the pests.

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I’m 3 days into what I consider to be the most peaceful place in the entire world: a 120-mile stretch of the northern Appalachian Trail, a thickly wooded land of shallow bogs, moss-wrapped trees, and long slivers of warm sunlight. Yet despite my blissful surroundings, I’m contemplating death. Crushed bodies litter the ground around me. Blood is smeared across my bare legs and combines with sweat to mat my hair to my head. My knuckles are red and swollen I tear at my flesh with my fingers and spin in violent, dizzying circles like a madman. I can see the end, and it isn’t pretty. I will perish in a dense fog of pain.

My torturer, the common mosquito, is pathetically small. In fact, its average length is less than that of a well-rubbed eraser and its weight on an empty stomach is a paltry 2 milligrams. In fact, the mosquito and its equally annoying cohort, the blackfly, are fragile at best when compared to most other members of Mother Nature’s arsenal of biting fauna. But as anyone who has entered mosquito or blackfly country can attest, size doesn’t matter. It’s the itch that counts. And it’s the swarming, when the cursed creatures descend upon a victim to feed, that ultimately drives you to the brink of insanity.

So, as I twirl and swat and cower and suffer, I beg for an answer to the following question: Why me?

“Because you’re there,” explains Bernard Greenberg, an emeritus professor of biology at the University of Illinois at Chicago. Nearly 3,500 species of mosquitoes and 1,600 species of blackflies have been identified around the globe. Only a fraction of these species serve as vectors of diseases like malaria, encephalitis, and yellow fever that kill millions of people every year. But more pertinent for the North American backpacker is that females need blood to reproduce. “And since you don’t have thick fur,” says Greenberg, “your nice bare skin makes a great target.” In other words, if you’re in the kitchen when the lunch whistle blows, look out.

In simplified terms, the life histories of mosquitoes and blackflies are very similar. They both begin as an egg. Where those eggs are laid depends on a number of environmental and physiological factors, but most important is the presence of water. “Blackflies prefer cold, running water,” explains Tacoma, Washington-based entomologist Terry Whitworth. “Mosquitoes tend to like still water.” For backpackers, these preferences spell trouble. Ponds, rivers, streams, even shallow pools of snowmelt-often the most scenic and inviting parts of the backcountry-are all common breeding grounds. And the breeding grounds are where adult biters binge.

Life as an adult biting fly is essentially an abbreviated period of bliss characterized by copulation, feeding (this is where you come in), and for the females, egg laying. Males survive on flower nectar and other plant juices. It’s the females-seeking protein for their eggs-that are out for blood. “They home in on the chemical cues given off by the animals that they’re seeking blood from,” explains Nolan Newton, a medical entomologist with the North Carolina Department of Environment and Natural Resources. “When they detect a plume of carbon dioxide being exhaled by an animal, they’ll fly upwind into that plume until they locate their prey.” Heat, moisture, odors from soaps and sweat, colors, and shapes also attract biters.

So, the big question for those who love the outdoors yet wish to avoid the torment is, “Do I have to stop breathing and sweating?” The answer, unfortunately, is that they’d still get you. The next question then becomes: When and where will the swarms be at their worst, and how do I avoid them? Sadly, altitude, topography, the weather, and countless other factors all combine to influence bug populations and their locations. “There are so many variables and so many issues,” laments Whitworth. “It’s very hard to predict.” While specifics are hard to pinpoint, scientists do know that biting activity in temperate areas is seasonal, peaking in late May to June; in warmer, tropical areas, it can continue unabated year-round. Also, some local areas track hatch activity and may have a better sense of regional trends (see for Maine blackfly hatches, for instance).

You can avoid the big bite by learning the bugs’ preferences. Blackflies disappear when the sun goes down, and “blackfly biting attacks are more severe in the mornings,” says Colorado State University entomologist Boris Kondratieff, though other experts also point to late afternoon and dusk as feeding times. “Mosquitoes are often more severe in the late afternoon, early evening, and at night,” adds Kondratieff.

Most biters prefer hot and humid weather, yet dislike direct sunlight. Therefore attacks tend to be more persistent when summer storms are threatening or it’s cloudy. As the temperature drops, winds pick up, and it begins to rain, the biters take cover and disappear-at least temporarily. Mosquitoes also require stagnant or nearly stagnant water to breed, and they thrive on the wet-dry cycle. “Anywhere from 6 to 10 days after a large thunderstorm or hurricane, and especially after flooding, you’ll find a big-time mosquito population of vicious biters,” says Kondratieff. That’s when you want to avoid places where water, including snow and meltwater, collects in depressions.

The bottom line: Watch the weather, talk to the locals, and develop a taste for snow camping.