The Living Animals of the World, Volume II: Birds, Reptiles and Amphibians, Fishes, Jointed Animals, Molluscs, etc.
of the World734 The Living Animals
The ROBBER-FLIES are large flies, with long, tapering bodies, of a black or partly yellow colour, and feed on smaller flies and other insects of different kinds. They have very thick, allied to these, but with ahairy legs, and a strong proboscis. A handsome Australian species, broader body, is represented in the Coloured Plate. is one of the most conspicuous of The HORNET ROBBER-FLY, represented on page 731, the British species. Among other places, it may be seen flying over the short grass at the top of the cliffs between Brighton and Rottingdean. They are very predaceous, and are probably rather beneficial than otherwise, by contributing to keep down injurious insects. But in North America there is a species called the BEE-KILLER, which is an extremely destructive insect, taking up its station in front of a hive, and killing large numbers of bees as they fly backwards and forwards from the hive.
The HOVER-FLIES are brightly coloured, rather smooth flies, and are familiar objects in gardens, and in open places in woods. They have the habit of hovering motionless in the air, and then darting off suddenly. Some of the larger species proceed from curious maggots, with long tails, which have been compared to the tail of a rat. These live in putrid water; and as the flies have a slight resemblance to bees, the fact is believed to have given rise to the old fable that bees are generated from the rotting carcases of oxen or other large animals.
The BOT-FLIES are remarkable for being parasitic on warm-blooded animals, their maggots living in tumours on the skin of oxen, known as "warbles," or in the stomach and intestines of horses, or in the nostrils and other cavities in the heads of sheep or deer. The HOUSE-FLIES and their allies form a very large group, is an autumn divided into many families. The true house-fly insect; but there are other flies which resemble it which live in houses at different times of the year. Most of them are harmless, although there is one species, very like a house-fly, which comes into houses in rainy weather, and inflicts a ,...,.,. P.'J,,,/./.,./, f.Part. Puncture like a gad-fly. This is the meaning of the popular BLUE-BOTTLE FLY, OB BLOW-FLY. saJinS that "the flies bite in rainy weather." This photograph shows the wings expanded. Although house-flies do not bite, yet they are sometimes exceedingly troublesome when they are in unusual numbers; and as they settle everywhere, they may convey infection mechanically, though not as the principal agents in the dissemination of definite diseases, like the mosquitoes. Thus, in Egypt, they are said frequently to convey ophthalmia, a very prevalent disease in that country.
The very first paper published in the " Transactions of the present Entomological Society " of London (for the existing Society had several short-lived predecessors) was a paper read by William Spence at the meeting on April 7, 1834, about a year after the Society had been "definitely founded, entitled Observations on a Mode practised in Italy of excluding the Common House-fly from Apartments." This desirable result is attained simply by stretching a net of white or coloured thread, with meshes of an inch or more in diameter, across an open window, which the flies will not venture to pass, if the room is lighted from one side only "for if there be a thorough light either from an opposite or side window, the flies pass through the net without scruple." Mr. Spence's son also referred to a passage in Herodotus where he says that Egyptian fishermen in his time defended themselves from the gnats by covering their beds with the nets which they had used in the day for fishing, and through which these insects, though they bit through linen or woollen, did not even attempt to bite. it is evidently well worthyThe matter seems to have been overlooked in recent years, though of consideration when flies or gnats are troublesome.
There is a conspicuous insect allied to the house-flies, but a little larger, measuring about half an inch in length. It is called the NOON-DAY FLY, and is often seen in considerable numbers, in the hottest part of the day, flying round and settling on the trunks and leaves of trees; it also settles on cow-dung. It is a shining black fly, with the sides and under surface
Twowinged Insects 735
of the head golden yellow in the male; the wings are transparent, slightly tinged with pale brown, and bright rusty yellow towards the base.
The African TSETSE-FLY is not very unlike a house-fly, and is one of the worst pests to cattle in those parts of Africa which it infests; for any horse, ox, or dog attacked by it will infallibly die after a longer or shorter period of suffering, though wild animals and sucking calves are not affected by it. It used to be supposed that the fly itself infused some deadly venom with its puncture; but later experiments have led naturalists to the conclusion that the fly is not itself poisonous, but that it forms the channel of communication of some fatal disease, just as some species of mosquitoes convey the infection of malaria.
The BLOW-FLIES, or BLUE-BOTTLES, of which there are several species closely allied to each other, are common in houses; and a smaller brilliant green fly, called the GREEN-BOTTLE FLY, is common on hedges. These are all flies which lay their eggs on fresh or putrid meat, when will also lay their eggsit is said to be " fly-blown." They in open sores; and in former days the sufferings of the wounded after a battle were often frightfully aggravated by this cause; and at the present day farmers would frequently lose sheep through their attacks, if they were not carefully tended in hot weather. Various species of flies in Eastern Europe, the Southern States of America, Jamaica, etc., habitually lay their eggs in the mouths or nostrils of men and animals, and the resulting maggots cause dreadful suffering and often death. In India, and especially in the Eastern Archipelago, there are some Regent's Park.brilliantly coloured, smooth, metallic blue and green flies as Photo by W. P. Dando, F.Z.S., big as humble-bees. There is also a family of flies allied to TSETSE-FLY. the house-fly, which have very bristly bodies, and are parasitic Destructive to' horses and cattle in Africa. on caterpillars, like ichneumon-flies.
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 antennae. These are the FOREST-FLIES and BIRD-FLIES, which attack horses and birds; and also some wingless insects, such as Photo by W. P. Dando, F.Z.S.],[Regent's Park. \ the so-called SHEEP-TICK (easily dis- TSETSE-PLY (ENLARGED). of the wings more distinctly.tinguished from a true tick by Showing the proboscis and veining possessing only six legs), the BEE-PARASITES, and the spider-like BAT-PARASITES. This parasitic group is also remarkable for depositing full-grown larvse or pupae 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 larvae 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 pupae 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 con- ' junction with rats, are believed to be among the photo by w. P. ixtndo, F.z.s.i (Cent's ra,k. principal agents in the spread of the plague. There BEE-FLY. ig another insect called the JIGGER, or SAND-FLEA, similar to the fly which destroys the locust eggs in Cyprus. 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.
USES OF FLIES.
flies are simply and solely It must not be supposed from the foregoing observations that less required inpests to man and beast, without any redeeming qualities. Their services are cold and settled countries, but in warm climates their value as scavengers can hardly be over-estimated. As regards the removal of carrion alone, Linnaeus 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.
Flies are also useful in keeping down the multitudes of destructive insects. Numbers of caterpillars fall victims to the bristly flies alluded to on the last page; and the Bee-flies, which form a family placed next to the Gad-flies, render far greater service in destroying locusts. They much resemble small humble-bees, being very much the same shape, and they are clothed with yellow down in the British species, and the transparent wings are conspicuously marked with black bands (as in the photograph above), or with brown shading and spots. The insects have a very rapid flight, and use their long proboscis to suck the honey of flowers; but their grubs are parasitic at least in some instances on wild bees; and it is life. But inprobable that their resemblance to bees has some reference to this mode of Cyprus, Algeria, North America, etc., the larvse of allied species feed inside the egg-cases of locusts, sometimes destroying as large a proportion as four-fifths of the whole brood. Locusts have many enemies, but it will easily be seen that the attacks of foes like these must reduce their numbers considerably, notwithstanding the swarms which frequently survive, and which are liable to the attacks of other enemies, such as robber-flies, locust-birds, etc., after they have actually arrived at maturity.