Summer World_ A Season of Bounty - Bernd Heinrich [61]
Because I’m a mostly diurnal animal and like sunny, open vistas, I have never been much bothered by our mosquitoes. Arctic ones are a different matter altogether, as for some reason mosquitoes get fiercer and more numerous the farther north you go. Caribou may become so depleted of blood by millions of teeming mosquitoes that they lose weight even while grazing full-time.
The only animals that consistently prey on mosquitoes are dragonflies, and they have probably been doing so for at least 100 million years. Mosquitoes seem to have habits that are designed to avoid overlapping with these predators. They avoid the sunshine, where dragonflies are most active, but hordes of mosquitoes appeared as soon as I stepped into dense shady woods where there were no dragonflies. That is, wherever and whenever dragonflies were scarce, mosquitoes were abundant.
Dragonflies that fly at dusk can cash in on mosquitoes. I suspect that the dragonflies’ extraordinary eyes developed to keep up with prey trying to escape into the dark. Behavioral adaptations have the same effect. While walking in grass in Botswana during the heat of the day, I saw mosquitoes spring up, and I was then followed by several dragonflies that were hawking them. The dragonflies seemed to be following me directly, because when I shifted to a slow jog they continued to follow me. They were acting like some species of birds—cowbirds in North America and cattle egrets in Africa—which also follow large animals because of the prey these animals flush.
Dragonflies are opportunistic. On the evening of 23 July 2005 at about eight o’clock, the air all the way down from our lawn to the beaver bog was full of huge dragonflies. Hundreds were visible, zigzagging back and forth—fairly low, about ten to fifteen feet above the ground. I had never before seen so many at once. Ten minutes later—the sun was still five degrees above the horizon and the honeybees were still working on the flowers—the dragonflies were suddenly done flying.
Mosquitoes are at times an irritation almost anywhere, to be sure, but by knowing their schedules one can avoid many of them. Mostly, this means staying indoors at night. The mosquitoes who get me while I sleep leave a tiny welt that disappears in a few minutes. Newcomers to the woods, who have not yet paid their “entry fee” to nature, don’t always get off quite so easy. It is not a good idea for bare buttocks to be exposed after dark, especially if one’s immune system has not yet been fine-tuned to receive their attention. Big red welts that itch to distraction are a consequence.
Blackflies fill in, and then some, where mosquitoes leave off. They are any of a number of species of small (about 0.08-inch) hunchback flies with thick stubby legs (all the better for crawling into your hair, and through creases and holes under your clothes), of the genus Simulium. Their larvae are filter-feeders that attach themselves to rocks at the bottom of swiftly flowing streams, often in such numbers that the rocks look coated with black mats of moss—but each “moss” frond is a larva. These larval mats may extend endlessly in a stream, and when the adults emerge half of them are hungry for blood. (The other half will be males who don’t need the protein meal.) The flies are silent—unlike mosquitoes, they emit no hum on their approach—and as soon as one surreptitiously lands, it starts sawing into the flesh. Blackflies drive moose to distraction, and affect some people even more severely. People who live near a wilderness or venture