Black Fly, a small dipterous insect, sometimes called gnat, midge, and sand fly, belonging to the genus timulium. The length of the common species (S. molestum) is about one tenth of an inch; the color is black, with transparent wings; the legs short, with a broad whitish band around them. They begin to appear in northern New England in May, and continue about six weeks; after them, however, comes another species (S. noci-vum), more numerous and smaller. These insects are a perfect pest in the subarctic regions, and so abundant in their season in the woods from Labrador to Maine, that travellers and anglers, unless of the most determined character, rarely venture far from the seashore. In bright still days they are innumerable, swarming in houses, flying in one's face, crawling linler tightly fitting garments, and there remain-ing. biting even in the night. Human beings and even dogs pass their lives at this season in a state of continual torment, much worse than amid the mosquitoes of the south. In cloudy weather, unlike the mosquito, they disappear. The bite is severe and stinging, each showing a point of blood, and followed by an irritation and swelling which last several days.
No veils nor gloves protect against their attack, as their small size enables them to penetrate wherever they choose. The best remedy seems to be a viscid ointment, into which tar enters, and which arrests and destroys them. The smaller midges which succeed them, called no-see-'em by the Indians from their minuteness, would hardly be seen were not their wings whitish mottled with black; they come forth in myriads toward evening, creeping under clothes, their bites feeling for the moment as if caused by sparks of fire; they do not draw blood, and there is rarely any swelling produced; they are most troublesome in July and August, and nothing seems available against their swarms, unless a thick smoke, quite as disagreeable, be considered a remedy. The larva and pupa are both aquatic, and the former is in some ponds as injurious to the raiser of young trout and other fish as the adult insect is to the angler for the adult fish. The larva, according to Mr. S. Green, spins webs under water as perfect as those of the spider, with equal mechanical ingenuity and rapidity, and in the same way, by fastening the threads at different points and going back and forth till the web is finished; the web is strong enough to destroy the fish while provided with the umbilical sac, by getting wound round the fins, head, and gills.
The buffalo gnat of the western prairies, a much larger species, has been known to bite horses to death; and an allied fly (rhagio), according to Westwood, is a great pest to man and beast on the confines of Hungary and Servia, and, it is said, will destroy cattle.