Summer World_ A Season of Bounty - Bernd Heinrich [60]
By far the majority of performers at this mating dance were males. In my sample of thirty, males outnumbered females twenty-eight to two. The dance is done primarily by single males, and the females are, as among wood frogs, presumably attracted by the communal male display. A male finds a female (or vice versa), and then they mate and leave the crowd. Once a male snags a female he tends to go steady with her, for a while. To test their fidelity to each other I put three couples that I had captured in a jar. One of these pairs, which had been on the ceiling in the early morning (presumably since the night before), separated instantly. The other two pairs, captured after the dance started, stayed together for about four and five hours respectively.
Fig. 26. Preliminary notes on and sketches of crane flies.
Despite their conspicuous presence and flamboyant behavior, I’m unable to determine what species they belong to. But that is not unusual—I have not seen and don’t know about the vast majority of species that live all around us, even the conspicuous ones. And new ones keep coming. In the summer of 2006 I saw for the first time huge flies with striking white faces and lemon yellow bellies. They were feeding on the meadowsweet flowers. I later learned that they were Belvosia bifasciata, a species of tachinid flies that specialize in parasitizing large caterpillars, particularly those of saturniid moths.
There are many insects with “fly” names (such as butterfly, dragonfly, ichneumon fly, and dobson fly), but there is only one group of true flies, the order Diptera (“two wings”). As the name of the order implies, its members are distinguished by having only two wings, rather than four as in all the others. Worldwide there are an estimated 240,000 species of true flies, but only about half have been described (i.e., named). (About 25,000 have so far been described in the United States.) Here in Maine, a group of about half a dozen fly species make up the deficit for most of us, in terms of familiarity. These all-too-intimate cohabitants of our summer world live in a vast geographical area stretching from the New England forests through the Canadian tundra. These animals (mostly mosquitoes, blackflies, midges, deerflies, and horseflies) seek us out in the flesh, rather than vice versa. We wish they would not. Because of their great numbers they are almost always memorable to those who meet them at the often very specific time in the summer that they claim as their ecological niche.
Dipterans attack animals, from caterpillars to caribou, in devious, ingenious, and horrible ways. For example, some eat their victims from the inside out, some from the outside in. But to be fair, the majority of the thousands of species are unobtrusive and can be enchanting. There are some who mimic wasps and colorful furry bumblebees; others have exotic forms that make them seem like aliens from outer space. Some are wildly beautiful, and there are many rare species that none of us will ever get to meet.
Every fly has its place and its season, and many flies have a specific time of day (or night) when they are active. Those that I know most intimately are not as entertaining as the dancing crane flies (there are also hundreds of species of these), who must remain anonymous for now, as I do not know their names. With regard to the next lot, who are familiar in summer, I shall be scarcely more specific and give only generic names.
Mosquitoes, the first on the list of familiar local dipterans, are the least objectionable, because, unlike species in the tropics, the northern species are not carriers of malaria, dengue fever, yellow fever, or other diseases, as far as we know. Female mosquitoes suck blood in order to get enough protein to make a few hundred eggs, which they deposit in water. The aquatic larvae filter-feed on microscopic