Tuesday, July 19, 2005

Deer Flies have Hatched

The Deer Flies Are Biting

I started out on a long anticipated nude backpacking trip to Deception Lake today and lasted all of fifteen minutes. I didn't even make the trail entrance. The moment I stepped from my car I thought I'd stepped into a hornets nest as dozens and dozens of large buzzing deer flies homed in on me and my car. The first of the season and it was a miserable moment as I stood there swinging my shorts around my head to push the insistent pests away.
[Image Source: Wikipedia]

I wasn't prepared for deer flies and their related cousins, the horse fly. Citronella does not work on them and DEET, though effective against mosquitoes, does nothing to discourage deer flies. These nasty critters can impart a nasty bite (the female is the bloodsucker . . . the male more civilized, or whimpish, as you prefer) as they suck your blood for a protein meal.

Like mosquitoes, they are attracted from hundreds of feet away by the carbon dioxide and lactic acid we exhale (which also explains why they had this affinity for the exhaust coming out of my cars tailpipe . . . carbon dioxide). In any case, within moments there were hundreds of these things buzzing around me and a naked hike was out of the question. It was all I could do to duck back into the car and listen to them impact against the windows. Nasty critters!

You find them everywhere . . . forests, meadows, roadsides. I noticed that they seem to prefer the sunnier areas (though I won't swear by that), and on the drive back down the mountain deer flies seemed to drop off below 3,600 feet. A little research indicates the deer fly is territorial and prone to locale. The west side of Mt Sawyer was deer-fly-free, so there may be some truth to this. The west side of Mt Sawyer is bereft of slower moving streams and wet areas, as well; and deer flies need a moist area to lay their eggs.

In a nutshell:

  • Deer Flies and Horse Flies pupate into adults once a year in the summer months and live as adults for 60 to 90 days.
  • The adults are attracted to dark, moving objects and the carbon dioxide we exhale and emit from the tailpipes of our cars.
  • The female Deer and Horse Flies bite with scissors-like mandibles and drink the blood from the bite. The bite can be extremely painful and some people may suffer an allergic reaction to the injected saliva that is intended to prevent coagulation.
  • Deer Flies favor the head, particularly under the brim of a hat. They will swarm the head and attack five or six at a time.
  • Horse Flies favor the legs and will attempt to attack with two or three flies at a time.
  • Deer Flies and Horse Flies will rest in grasses or bushes and swarm when they detect a victim. They are strong fliers and will aggressively follow a car for a considerable distance.

Additional information on the various biting flies can be found at the Colorado State University Cooperative Extension.

REI has the only product I know of that is effective against biting flies such as the Deer and Horse Fly.

To quote the product literature:

Sawyer Broad Spectrum Spray

For skin application. While Deet can repel all mosquitoes, ticks, and some flies, Deet does not repel all flies effectively. For those situations you will need the extra protection of the special fly repellent, R-326, which is added to this formula and is effective against flies, gnats and no-see-ums. For times when sprays are more convenient than lotions, this is the formula to use. Sawyer's Broad Spectrum contains no alcohol which has been shown to increase skin absorption of Deet, and is the only non-alcohol spray repellent in the USA.

You can order it online here, or pick up a bottle at the downtown REI for $5.95

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