Summer World_ A Season of Bounty - Bernd Heinrich [59]
Why does the sugar borer’s population not skyrocket? Why does the borer not eat all that it can until its main resource, sugar maple trees, has been devastated? What prevents the familiar, often frightening scenario that is generally avoided only because of parasites, diseases, and predators that multiply as soon as the population increases above a critical level? Nobody knows. This is not rocket science, but it too is complicated.
The sugar borers have achieved, or are held to, something enviable. They are in a world of plenty, so none go hungry, destroy their habitat, or jostle and interfere with each other. Somewhere there is a check on their natural rate of increase, and you can be sure of one thing—that if they could tell us what they wanted at any one time, they would vote to obliterate the forces that hold them in check, the forces that ensure their long-term benefits. And so, probably, would we, if we voted merely on the basis of our individual interests.
13
Flies
We breed ’em, you feed ’em.
—BUMPER STICKER OF
THE MAINE BLACKFLY BREEDERS ASSOCIATION
21 June 2007. IT’S THE SUMMER SOLSTICE (IN THE NORTHERN hemisphere), and according to my calendar, which only one species goes by, it’s the “first day of summer.” But for many species summer has actually been in progress for months, and it’s now arguably the middle of summer—when the days are longest as the Earth’s axis tilts the most toward the sun. The hottest days, though, are still to come. In any case, it’s sufficient reason to celebrate, and what better way than to enjoy a dance performance?
As chance would have it, I find one. It’s right here at my camp in the Maine woods. The dance is in the outhouse, presented by a special troupe of untiring performers. I’m just a spectator today, and viewing conditions are perfect. It’s a pleasant 70°F—too cool for horse and deer flies and too dry for blackflies and the god-awful midges, the scourge from hell.
Our outhouse is open at the front, and it faces deeply shaded sugar maple woods. The dancers—two or three dozen of them—each have six long, spindly legs. They jitterbug up and down and forward and back in a dark corner just under the roof, and they are worked up to a frenetic speed. Undoubtedly they are expert performers. They ought to be. They’ve probably been doing one or another version of their act for more than 225 million years, since the Triassic period. And indeed, their performance doesn’t disappoint.
Most of the dancers are single, but several have partners to whom they are firmly attached—by their genitals. The members of a pair face in opposite directions, and when—more often than the singles—they come to rest, they dangle with one holding on to the ceiling with its front legs while the other dangles below.
The dance was still going at full throttle at one-thirty PM, when with one swoop of my insect net I went through the throng and captured about thirty of them for a closer look. (A couple of hours later there were as many there again, and they continued for at least the next two days, from about eight AM to eight PM every day. Who knows? Maybe they dance at night, too.)
Superficially they resembled huge mosquitoes. They are relatives of this group of insects, commonly known as crane flies because of their very long legs. Their bodies were about a third of an inch, while their legs were three times longer. Their legs drop off at the merest touch, an adaptation for making a quick getaway from a predator. But these didn’t get away, even as my sweep of the net left the bottom of it littered with a small pile of loose legs. These flies all looked similar, except for their genitalia. Of a pair I examined, one had a thicker but pointed abdomen,