Chapter II: Insects (3)

A grey moth, with pink bands on the body.]

[_Smyrna._

GREAT PEACOCK-MOTH.

Brown with pale borders. The largest moth found in Europe.]

[_Washington._

POLYPHEMUS MOTH.

On leaves of linden-tree, just out of cocoon. A native of North America.]

"In the last month of summer the order was given to the female officers to dye the silk of various colours, in order to weave chequered sarcenets, comprising black and white, black and green, green and red, with red-and-white checks--all of which was to be done according to the ancient rule, without the least variation; the black, yellow, azure, and red tints were all to be correct and good, without the least fault, in order to provide dresses for the celestial and ancestorial sacrifices, and standards for distinguishing the high and low degrees.

[_Milford-on-Sea._

WHITE PLUME-MOTH.

A very delicate insect. The wings are cleft almost to the base into separate feathers, two on the fore wings and three on the hind wings.]

"In ancient times the emperor and his princes had a public mulberry garden and a silkworm establishment erected near some river. On the morning of the first day of the third month of spring, the sovereign, wearing a leather cap and a plain garment, ascertained by lot the chief of his three queens, with the most honourable amongst his concubines, and caused them to attend to the rearing of the silkworms in the above-named establishment. They then brought the eggs of the worms, and washed them in the river above alluded to, after which they picked the mulberry-leaves in the public garden, and aired and dried them, in order to feed the worms.

[_Milford-on-Sea._

INDIAN SWALLOW-TAILED MOTH.

Resembles the American Luna Moth figured on page 718, and of an equally delicate green.]

"When the season was over, the royal concubines, having completed the business of rearing the silkworms, brought the cocoons to show them to the prince, when he presented the cocoons again to his consort, whereupon his consort said, 'This is the material of which your highness's robes are to be formed.' Having said which, she covered herself with her robe, and received the cocoons. On this occasion the ladies of the court were honoured with the present of a sheep. This was the mode in which the presentation of the cocoons was anciently conducted."

In the reign of Justinian eggs of the Chinese mulberry-silkworm were smuggled into Europe by two monks, and the culture of silk rapidly spread through Southern Europe, where it has continued to form a staple industry ever since. In the Peloponnesus especially such large plantations of mulberry-trees were grown for the purpose of rearing silkworms as to give the peninsula its modern name of Morea. Silk is obtained in different parts of the world from the cocoons of various other moths, chiefly belonging to the group of Emperor-moths; but these products are only of local importance, and are not likely to compete with the mulberry-silkworm.

HALF-WINGED INSECTS, OR BUGS AND FROG-HOPPERS.

BY W. F. KIRBY, F.L.S.

SHIELD-BUG.

In tropical countries these bugs are often as large as cockchafers.]

Some species of this family are carnivorous as well as herbivorous.]

The order including the Bugs and Frog-hoppers is divided into two sub-orders. There are also one or two small groups, sometimes treated as separate orders, and sometimes regarded as aberrant sections of the order, to which we shall allude later.

The TRUE BUGS have their fore wings of a horny texture, but generally overlapping, and the extremities form a transparent membrane, resembling that of the hind wings. They have a long sucking-proboscis curved down beneath their bodies, and their antennæ usually consist of only four or five long joints. Most are vegetable-feeders, but some species feed on the juices of other insects, while a few attack warm-blooded animals, either casually or habitually.

The first family includes the SHIELD-BUGS. These derive their name from the unusual development of a part of the thorax called the "scutellum." In most insects it is only a small plate of no great importance, attached to the end of the thorax; but in the Shield-bugs it forms a great solid arch, covering the whole of the wings, and protecting them as the wing-cases protect the wings of beetles. There are only a few small species in England, but a great number of beautiful species inhabit warm countries, some of a brilliant blue or green or yellow, or spotted. Many of them are comparatively large insects, nearly an inch long, and resemble brilliantly coloured beetles, from which, however, they can easily be distinguished by the antennæ, the proboscis, and the shield, the latter of which is not divided down the middle like the wing-cases of beetles.

[_Colesborne._

LACE-WING BUG.

An elegant little insect, injurious to pear-trees.]

Next to the Shield-bugs, and considered by many entomologists as belonging to the same group, are the PENTAGONAL SHIELD-BUGS, so called because the scutellum, though much smaller than in the Shield-bugs, is often half as long as the abdomen, and forms a broad triangle, sometimes broken at the sides, so as to make a five-sided plate, lying above the bases of the wings. Several green or brown species of this family, about half an inch long, are common in England among bushes. Many have a very disagreeable smell, and hence they are called STINK-BUGS in America. They feed on vegetable juices, and also frequently on soft-bodied insects. Several species (chiefly foreign) among the Shield-bugs and the present group have a strong spine, or else a blunt protuberance, projecting from each shoulder.

The remaining plant-bugs are much more numerous--at least in England--than those already mentioned, and form several families, which cannot be noticed in detail. Many species are rather small and delicate creatures, narrower and softer than the Shield-bugs and Pentagonal Shield-bugs, and are adorned with various colours, black and red predominating. Some have more transparent wings than the others, such as the beautiful little LACE-WINGED BUGS, one species of which is often very destructive to pear-trees.

The BED-BUG is a reddish-brown, somewhat oval insect, common in many old houses, hiding in cracks and crevices in walls and woodwork, and coming out at night to suck the blood of sleepers with its sharp proboscis. There are allied species, sometimes found in hen-houses, pigeon-houses, and places where bats congregate. The bed-bug has only been known in England for a few centuries, and though now a great pest in all parts of the world, was probably a native of Africa originally.

The bed-bug, notwithstanding its offensive odour, is preyed upon by several other insects, among which are the common cockroach and the MASKED BUG. The latter is a black-winged bug about three-quarters of an inch long, and remarkable for the habits of its larva, which conceals itself with dust or fluff, so that it may steal upon its prey unobserved. The masked bug and its larva feed on soft-bodied insects of various kinds, and are more frequently found in outhouses than in dwelling-rooms. This bug occasionally attacks warm-blooded animals; and a short time ago a great deal of nonsense was published in the newspapers about a mysterious insect-pest in North America, called the KISSING-BUG, which seems to have been nothing more unusual than this insect. There are, however, some much larger species belonging to the same family, which are formidable pests in the Southern States of North America, Chili, and various other countries.

MASKED BUG.

The larvæ of these insects cover themselves with dust, in order to creep upon their prey unnoticed.]

After these insects come the WATER-BUGS, of which there are several families, though the number of species is comparatively small. Some are very slender insects, with long, slender legs, and may be seen running on the surface of ponds in England; while others, which are tropical species, are marine, and are met with running on the surface of the water in the open sea.

The largest members of the group are some of the great water-bugs found in Africa, India, and America. Their fore wings are of a light brown, and measure from 3 to 5 inches in expanse. Their legs are short and strong, and the front legs are adapted for grasping their prey, which consists of insects and small fishes. There are some smaller species in which the female lays her eggs in a cluster on the back of the male, which carries them about till they are hatched. These bugs fly about in the evening, and are frequently attracted by electric light.

In England there are two allied species called WATER-SCORPIONS, from their long front legs, which somewhat resemble the nippers of a scorpion. The commonest is a brown insect, with the abdomen red beneath. It is about an inch long, including the breathing-tube, which sticks out behind the body like a tail, and is formed of two separable parts. It is an oval insect, half as broad as long, and is common in stagnant water. The other species is twice as long, and is much more slender, with longer and more slender legs. It is yellowish brown, like most of the other water-bugs, and is a sluggish and rather scarce insect, creeping about in the mud at the bottom of deeper water than that preferred by the commoner species.

The WATER-BOATMEN are yellowish-brown insects, measuring half an inch in length, with smooth bodies, and long, hairy hind legs, with which they row themselves about on the water, as if with oars, while floating on their backs. All the larger water-bugs are capable of inflicting a severe puncture with their sharp proboscis, if handled incautiously.

[_Regent's Park._

GREAT WATER-BUG.

Very similar species are found in Africa, Asia, and America.]

[_Regent's Park._

GREAT WATER-BUG.

These insects live in water during the day, and fly about in the evening.]

The FROG-HOPPERS and their allies differ from the Bugs in the fore wings being uniform in texture throughout, and not membranous, with the tips transparent. Sometimes the fore wings are of a more or less horny texture, but they are frequently as transparent as the hind wings. All the species are plant-feeding insects.

[_Colesborne._

INDIAN CANDLE-FLY.

Erroneously stated to be luminous.]

The first family, the CICADAS, includes a number of large or moderate-sized species, in which the males are provided with a large, drum-like apparatus on the abdomen, and some of which make the loud noise for which they have long been celebrated. There is only one comparatively small species in England, which is rare, and almost confined to the New Forest. It is black, with transparent wings, about 1½ inch in expanse, and has red transverse lines on the abdomen. The largest Indian species, however, sometimes expands 8 inches. Cicadas have broad heads, broad short bodies, ending rather abruptly in a point, and their larvæ live in the ground, where they are sometimes injurious to the roots of trees. The wings are usually, but not always, transparent--a very common Indian and Chinese species, about 3 inches in expanse, being black, with large yellow spots on the fore wings. In North America and Australia cicadas are often miscalled Locusts.

The LANTERN-FLIES, or CANDLE-FLIES, which form the next family, derive their name from having been stated to be luminous, a statement which is now considered very doubtful. They are insects of considerable size and bright colours, occasionally resembling butterflies and moths; the largest species, the LANTERN-FLY of South America, sometimes measures as much as 5 inches across the wings, which are of a pale yellowish or greenish tint, with a large round spot on the hind wings, formed of black rings or crescents, and enclosing one or two large white spots. On the head is an immense hollow, blunt protuberance, marked with one or two longitudinal red lines. In some species there is a curved horn in front of the head; in some the horn forms a short cross; in others it ends in a red knob; while others are destitute of such an appendage. The hind wings are often brightly coloured, red or yellow usually predominating.

The TRUE FROG-HOPPERS are small insects about a quarter of an inch long, found among grass and bushes. The fore wings are of rather a stout consistency and uniform in colour (often yellowish), and the hind wings transparent. The larvæ are soft grubs, and live in the masses of froth so common in grass and bushes, which are vulgarly known as "cuckoo-spit."

Passing over several families of small species, we arrive at two which contain many very destructive insects. The APHIDES, PLANT-LICE, or SMOTHER-FLIES are the small green or brown winged or wingless insects which frequently cover the shoots of roses and other trees and plants, and exude a sweet sticky substance, called "honey-dew," very attractive to ants. One species, known as the AMERICAN BLIGHT, is extremely destructive to apple-trees, patches of a substance resembling white cotton appearing on the bark. Under these patches the bark rots from the attacks of the insects, the pest being very difficult to eradicate.

APHIS.

A sexual wingless form.]

SCALE-INSECT.

The females die, covering their eggs with their own bodies.]

SCALE-INSECTS.

Showing their appearance when crowded together on a branch.]

Many of the Aphides exhibit the curious phenomenon known as "alternation of generations." The first brood consists of winged males and females; but the eggs which the latter lay produce exclusively wingless females, or rather sexless creatures capable of laying eggs, and these multiply indefinitely for a time, till perfect males and females are again reproduced. In some cases the winged forms live on the leaves of trees, and the wingless forms at the roots of grass, etc. One of the most destructive of all these insects is the VINE-APHIS, which was probably introduced into Europe from America, and which threatened at one time almost to destroy the vine industry in France. Wingless sexless forms live and multiply at the roots of vines; and in summer winged males and females are produced, which fly up, and lay eggs on the leaves; while some of the wingless insects also quit the ground, and form small galls on the vine-leaves. Although very abundant in America, the insect is not nearly so destructive to the plants which it attacks as in Europe.

Some species of SCALE-INSECTS are almost equally destructive, especially to greenhouse plants. The male is slender and two-winged, but the female is wingless and often legless, and after depositing her eggs usually dies above them, thus forming a covering to protect them from injury. Cochineal consists of the bodies of a species of scale-insect which infests the leaves of a cactus in Mexico.

The TRUE LICE are found on various species of mammals, and imbibe their food through a proboscis. The BIRD-LICE, or BITING-LICE, form a well-defined group by themselves. They are sometimes regarded as forming distinct orders of insects; but some authors treat the first group as a degraded family of insects allied to the Frog-hoppers, and the second group as an equally degraded and aberrant family allied to the Lace-winged Insects.

TWO-WINGED INSECTS, OR FLIES.

BY W. F. KIRBY, F.L.S.

This order of insects is probably one of the most numerous in individuals, though it may be that, when we know more of the insect population of the world, we shall find that it is outnumbered in species by the Beetles or the order to which the Bees and Ants belong. It differs from all other orders in possessing only two wings instead of four, which is the usual number in insects. The metamorphoses are complete, and the mouth is furnished with a proboscis for imbibing liquid food. Hind wings are represented in many species by a pair of organs called "poisers," resembling a knob at the end of a stick, and other species have two small additional lobes attached to the wing, called "winglets "; but there is no such thing as a really developed hind wing in any insect belonging to the group. They are always two-winged flies, except in the case of a few aberrant species, such as the Fleas, in which no wings, or only mere rudiments of wings, are to be met with. The Gnats, Daddy-long-legs, and House-flies are among the commonest representatives of this order.

[_Smyrna._

CICADA AND PUPÆ.

Noted for the loud drumming sound produced by the males.]

The first section of the group includes the GNATS and the DADDY-LONG-LEGS, or CRANE-FLIES, the members of which may be distinguished by having moderately long antennæ, composed of more than six joints, and never terminating in a bristle. They are all vegetable-feeders, with the exception of the females of gnats and sand-flies, which are furnished with a lancet-like arrangement for sucking the blood of warm-blooded animals.

The GALL-FLIES, WHEAT-MIDGES, etc., have rather long, jointed antennæ, which are not feathered, though sometimes tufted on the sides, and their maggots produce small galls on various trees and plants, or distort and otherwise injure them. They resemble small gnats, and there are two particularly destructive species which attack corn in England and elsewhere,--the WHEAT-MIDGE, an orange-yellow fly with black eyes, which produces little yellowish or reddish maggots which injure the growing grain in the ear; and the HESSIAN FLY, which is brown, and produces semi-transparent maggots, which afterwards grow darker, and when full grown become pupæ resembling flax-seeds. The maggots attack the stalk, feeding on the sap till the stalk cracks and bends over. This is an infallible sign of their presence, and of the mischief they are doing.

Among the best-known insects of this group are the GNATS, or MOSQUITOES, of which there are many genera and species. There is no difference, however, to permit of their being classified in two separate popular categories. In England any of these troublesome insects are called Gnats; out of England they are termed Mosquitoes, if we are tormented by them, even though they may belong to the same species as the English ones--for "mosquito" is merely the Spanish word for "gnat" Anglicised.

Observe the proboscis in front of the head.]

Gnats breed in standing water, fresh or otherwise, but seem to prefer rain-water, for they are very numerous about small pools and water-butts. Consequently they were formerly far more abundant in England than at present, when the fens were still undrained, and when every house had its rain-water butt. The females of some species construct small rafts of eggs, which float about on the surface of the water till hatched, and then produce small maggots with a breathing-apparatus at the end of the tail. In this condition they swim head-downwards, while the more compact pupa floats head-upwards. They may be destroyed by pouring a little kerosene into their breeding-places; and as this floats on the surface of the water, it does not interfere with the use of the water in water-butts, which is usually drawn off by a tap below. The males of gnats often have feathered antennæ and long, slender legs. The females, however, are more nocturnal in their habits, and come into houses in the evening, and keep people awake by their humming and painful "bites," or rather punctures, which frequently cause a distressing irritation for a day or two afterwards. What is worse is that they are now known to disseminate various diseases, such as elephantiasis and also malarial fever of every kind, in this manner--from the comparatively mild ague of the English fens (now nearly extinct) to the terrible malaria of Southern Europe, India, and Africa, formerly attributed to the unhealthy atmosphere of marshy countries, or to exposure to the night air in warm countries, but now known to be caused by the bites of the gnats, or mosquitoes, which breed in swampy places, and fly about in the evening. It is believed that only certain species of gnats convey the germs of these diseases; and it has been stated that, though ague-bearing species of gnats are still found in England, those which have been examined for the purpose have been free from these germs, and are therefore incapable of propagating the disease.

HORNET ROBBER-FLY.

Common in the south of England.]

[_Regent's Park._

DADDY-LONG-LEGS.

Large species, with variegated wings.]

In many parts of the world gnats are excessively numerous and troublesome at certain seasons of the year, filling the air like clouds of dust, so that it is difficult to sleep or eat from the annoyance and irritation caused by their attacks. This will be readily credible to those who have experienced the pain which they cause even when not very numerous, and have been kept awake at night by their shrill piping as they approach. They appear to be equally numerous in cold and warm countries--Lapland, France, South Russia, Italy, various parts of America, and in fact most parts of the world being liable to the inordinate multiplication of different species.

In England they were formerly so abundant in the fenlands that mosquito-curtains were in use less than a century ago, and may be so still. But their numbers have so diminished of late years that, whenever gnats are a little more troublesome than usual, it is reported that there has been an invasion of mosquitoes. A year or two ago there was a report that "mosquitoes" had been brought to Cromer in some fishing-vessel, and the newspapers contained paragraphs about "mosquitoes" having caused much annoyance in different parts of London. But many of the specimens submitted to the inspection of entomologists proved to be nothing more than the commonest of all the blood-sucking gnats, called the PIPING-GNAT by Linnæus, on account of its shrill note. The note is produced by the rapid vibration of the wings, which has been estimated at the rate of 3,000 per minute. Gnats do not always fly near the ground. Sometimes they have been seen ascending from cathedrals and other high buildings in such vast swarms that they resembled clouds of smoke, and gave rise to the idea that the building was actually on fire.

Equally troublesome and annoying are the SAND-FLIES, as they are called in England, or the BLACK-FLIES, as they are called in America. They are very small flies, short and broad, and with broader wings than gnats; and one of them, which actually destroys many mules and other domestic animals in the Mississippi Valley, as we learn from Professor Comstock, is called the BUFFALO-GNAT, from a fancied resemblance of the side-view of the insect to a buffalo. Other species are equally destructive to the cattle in the Banat of Hungary. It is a curious circumstance that, in the case of nearly all two-winged flies which attack men and animals, it is usually only the females which suck blood, the males frequenting flowers and being perfectly harmless.

HOVER-FLY.

This fly has a superficial resemblance to a bee. (See page 734.)]

Common in filthy water.]

Respecting mosquitoes in South America, Mr. H. W. Bates writes, in his work "The Naturalist on the Amazons," when passing a night in a boat about twenty-five miles from the town of Villa Nova: "At night it was quite impossible to sleep for mosquitoes; they fell upon us by myriads, and without much piping came straight at our faces as thick as rain-drops in a shower. The men crowded into the cabins, and then tried to expel the pests by the smoke from burnt rags; but it was of little avail, although we were half suffocated during the operation." But the sand-flies, encountered a little higher up the river, were much worse: "We made acquaintance on this coast with a new insect-pest, the Piúm, a minute fly, two-thirds of a line in length, which here commences its reign, and continues henceforward as a terrible scourge along the upper river, or Solimoens, to the end of the navigation on the Amazons. It comes forth only by day, relieving the mosquito at sunrise with the greatest punctuality, and occurs only near the muddy shores of the stream, not one ever being found in the shade of the forest. In places where it is abundant, it accompanies canoes in such dense swarms as to resemble thin clouds of smoke. It made its appearance in this way the first day after we crossed the river. Before I was aware of the presence of flies, I felt a slight itching on my neck, wrist, and ankles, and, on looking for the cause, saw a number of tiny objects, having a disgusting resemblance to lice, adhering to the skin. This was my first introduction to the much-talked-of Piúm. On close examination, they are seen to be small two-winged insects, with dark-coloured body and pale legs and wings, the latter closed lengthwise over the back. They alight imperceptibly, and, squatting close, fall at once to work, stretching forward their tiny front legs, which are in constant motion, and seem to act as feelers, and then applying their short, broad snouts to the skin. Their abdomens soon become distended and red with blood, and then, their thirst satisfied, they soon move off, sometimes so stupefied with their potations that they can scarcely fly. No pain is felt whilst they are at work, but they each leave a small circular raised spot on the skin, and a disagreeable irritation. The latter may be avoided in great measure by pressing out the blood which remains in the spot; but this is a troublesome task when one has several hundred punctures in the course of a day [like Prince Siror, in one of Bulwer Lytton's stories, who fell "pierced by five hundred spears"]. I took the trouble to dissect specimens, to ascertain the way in which the little pests operate. The mouth consists of a pair of thick fleshy lips, and two triangular horny lancets, answering to the upper lip and tongue of other insects. This is applied closely to the skin, a puncture is made with the lancets, and the blood then sucked through between these into the oesophagus, the circular spot which results coinciding with the shape of the lips. In the course of a few days the red spots dry up, and the skin in time becomes blackened with the endless number of discoloured punctures that are crowded together. The irritation they produce is more acutely felt by some persons than others. I once travelled with a middle-aged Portuguese who was laid up for three weeks from the attacks of Piúm, his legs being swelled to an enormous size, and the punctures aggravated into spreading sores."

HOUSE-FLY (MALE AND FEMALE).

The larvæ of the house-fly live in refuse, so do not thrive where cleanliness abounds.]

However, the traveller in Amazonia has one consolation: the great rivers which traverse the forests are of three different colours; and the black-water rivers--so called from the dark colour of the water, owing apparently to the amount of vegetable matter which they hold in solution--are never infested with mosquitoes. Probably the character of the water renders it unsuitable to them for breeding purposes.

The CRANE-FLIES, or DADDY-LONG-LEGS, are also very injurious insects, but in a different manner, for their subterranean maggots feed on and destroy the roots of grass in the same way as the grubs of the Cockchafers. They are insects of considerable size, with slender bodies, terminating in a short, horny point (the ovipositor) in the female, and with long, slender legs, which are liable to break off at the least touch. The commonest species has a grey body and transparent wings; but there is a larger one with the wings prettily variegated with brown, and a smaller one in which there are yellow markings towards the end of the body.

The more typical FLIES have usually shorter and broader wings, and thicker, shorter, and more hairy legs, than those just mentioned; and the antennæ have usually only three or four joints, and are often furnished with a long, slender bristle at or before the end of the last joint.

As in the case of the Gnats and Crane-Flies, so as regards the more typical Flies, we have only space to notice a few of the more important families.

Some of the GAD-FLIES are no larger than house-flies, but others are as large as wasps or larger, with broader wings, and of a black, grey, or yellowish colour; they frequent fields, and settle on cattle, or on our clothes or hands. Some have transparent and others dark-coloured wings, but they are all capable of inflicting a severe puncture, often sufficient to draw blood, even in the case of the smaller species.

BLUE-BOTTLE FLY, OR BLOW-FLY.

These flies deposit their eggs on meat, when it becomes "fly-blown."]

The prettiest of the gad-flies are the GOLDEN-EYED FLIES. They are black, with the abdomen more or less marked with yellow; and black, or black and transparent, wings. The eyes are of a beautiful golden green, dotted and lined with purple. They are moderately stout insects, about the third of an inch long, and are not uncommon. Another insect, known as the BLOOD-SUCKING RAIN-FLY, has a rather long and slender body for a gad-fly, and is nearly half an inch long. It is of a lighter or darker grey, with reddish markings on the sides of the abdomen in the male. The wings are greyish brown with whitish dots, and a white mark towards the tip. Both these flies are very troublesome, the latter chiefly on the edges of woods or near water, especially in rainy weather.

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, hairy and a strong proboscis. A handsome Australian species, allied to these, but with a broader body, is represented in the Coloured Plate.

The HORNET ROBBER-FLY, represented on page 731, is one of the most conspicuous of 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.

BLUE-BOTTLE FLY, OR BLOW-FLY.

This photograph shows the wings expanded.]

The HOUSE-FLIES and their allies form a very large group, divided into many families. The true house-fly is an autumn 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 puncture like a gad-fly. This is the meaning of the popular saying that "the flies bite in rainy weather."

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. The matter seems to have been overlooked in recent years, though it is evidently well worthy 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 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.

TSETSE-FLY.

Destructive to horses and cattle in Africa.]

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 it is said to be "fly-blown." They will also lay their eggs 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 brilliantly coloured, smooth, metallic blue and green flies as big as bumble-bees. There is also a family of flies allied to the house-fly, which have very bristly bodies, and are parasitic on caterpillars, like ichneumon-flies.

[_Regent's Park._

TSETSE-FLY (ENLARGED).

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.

[_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.

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 bumble-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 probable that their resemblance to bees has some reference to this mode of life. But in Cyprus, Algeria, North America, etc., the larvæ 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.

Nor must we omit to notice the use of flies as articles of food for man or useful animals. Many persons are very fond of cheese-hoppers, which are really the maggots of a small fly; and we read in Kirby's "Textbook of Entomology," page 92: "The Rev. A. E. Eaton informs me that he believes that two species of _Ephemeridæ_ (May-flies) form a portion of the so-called 'Kungu Cake,' manufactured by the natives of South Africa of gnats, and probably any other insects which can be obtained in sufficient abundance." "Gentles," which are the maggots of flies, are used by anglers for ground-bait.

PORTION OF INSHORE CORAL REEF AT THURSDAY ISLAND, TORRES STRAITS.

In the foreground are hemispherical masses of the so-called Brain-Stone and Star-Corals. In the background the rocks are encrusted with various species of soft-fleshed corals allied to the similar "Dead Men's Fingers" of the British Seas.]

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_BOOK VI. SHELL-FISH, LAMP-SHELLS, SEA-URCHINS, STAR-FISHES, MOSS-ANIMALS, WORMS, CORALS, JELLY-FISHES, AND SPONGES._

BY W. SAVILLE-KENT, F.L.S., F.Z.S.

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