Showing the proboscis and veining of the wings more distinctly.
There are other flies which easily attract attention, such as the yellow hairy fly found about cow-dung, and some rather small species with prettily variegated wings, which feed on flowers or fruit. The cheese-hoppers are also the maggots of a small black fly.
Besides these, there are some aberrant parasitic families of flies with long, hairy legs, and only one or two joints to the antennæ. These are the Forest-flies and Bird-flies, which attack horses and birds; and also some wingless insects, such as the so-called Sheep-tick (easily distinguished from a true tick by possessing only six legs), the Bee-parasites, and the spider-like Bat-parasites. This parasitic group is also remarkable for depositing full-grown larvæ or pupæ instead of eggs.
The Fleas are a small group of small wingless insects, with such powers of leaping that it has been said that if a man was as agile as a flea he could jump over the dome of St. Paul's. The larvæ of fleas are small, worm-like creatures, with bristles, but without legs; they probably live on any sort of animal or vegetable refuse. They subsequently change to pupæ in small cocoons, and emerge as perfect fleas, which live by sucking the blood of warm-blooded animals; or, when that fails them, they may attack caterpillars, or other small soft-bodied creatures. Though not very particular about their food, different species are more or less attached to different animals; and while in Europe the most troublesome species is the one considered to be most particularly attached to man, the species most troublesome in North America is known in Europe as the Dog-flea. They are all very similar in habits and appearance. Fleas are not only annoying, but, in conjunction with rats, are believed to be among the principal agents in the spread of the plague. There is another insect called the Jigger, or Sand-flea, common in most of the warmer parts of America, and which has more recently been introduced into Africa. The female burrows into the feet of men or animals, where her body swells up with eggs to the size of a pea; and serious and sometimes fatal ulcers are the ordinary result, unless the insect is carefully extracted at an early stage of the attack.
Photo by W. P. Dando, F.Z.S.] [Regent's Park.
BEE-FLY.
Similar to the fly which destroys the locust eggs in Cyprus.
Uses of Flies.
It must not be supposed from the foregoing observations that flies are simply and solely pests to man and beast, without any redeeming qualities. Their services are less required in cold and settled countries, but in warm climates their value as scavengers can hardly be over-estimated. As regards the removal of carrion alone, Linnæus declared that the progeny of only three blow-flies would devour the carcase of a dead horse as quickly as a lion—a statement which, even if slightly exaggerated, conveys a vivid idea of their voracity and the rate at which they increase.