Chiefly includes brightly coloured flies, marked with yellow or red and black bands or patches (Fig. 67), and flying rapidly with a buzzing noise. They can remain suspended at the same point in the air by moving their wings up and down with great rapidity. A few of them resemble the humblebee in their thick covering of hair; others, with yellow and black abdomen, look like wasps (Syrphus). The proboscis is adapted for sucking, but not for piercing; these flies suck their food from flowers. They are fond of hovering in the air in sunny places. The legless larvæ vary, according to species, in their habits, and consequently in their structure. Some (those of the Drone Flies, Eristalis) live in stagnant water; others (e.g. those of Eumerus lunulatus) live in onions, which they hollow out; while some, again, develop in rotten wood, etc. The maggots of the Aphis-eating Flies (Syrphus), however, feed on insects, chiefly aphides, which they suck out completely. They are elongated, tapering in front, thickened behind, move like leeches, and vary much in colour (green, yellow, brown, chequered), according to the species. As they grow quickly, and consequently more than one generation is found each year, and as they are very voracious, we must look upon them as powerful allies for the extermination of aphides.

Family: Stomoxydæ (Stable Flies).

In many points the stable flies resemble ordinary flies, but their mouths are adapted for piercing. Their painful bites make them known to every one as pests to human beings and cattle. Here belongs the common Stable Fly (Stomoxys calcitrans), a form often confounded with the house fly, but distinguished from it by a sharp proboscis projecting at right angles, besides which the abdomen is more of a yellowish grey. The maggots usually live in dung. Two generations yearly: the first flies about in March; the second, and much more numerous one, in August and September. Remedies: Cp. p. 165.

Family: Œstridæ (Bot Flies).

Medium-sized or large flies (Fig. 121), with thick hemispherical heads, and mouth-parts not strongly developed. The antennæ can be drawn back into deep pits. The hot flies make a buzzing sound during flight. The headless, twelve-ringed maggots live in the bodies of various mammals. Their skin is provided with numerous wart-like projections, or circlets of spines. When very young the maggots are elongated and cylindrical, and then possess a mouth-hook, which disappears during the later moults. As soon as the maggots are fully developed they leave the body of the animal they inhabit, and let themselves fall to the ground, where they become pupæ within the shrivelled larval skin.

The following genera are distinguished: Warble Flies (Hypoderma), and Bot Flies (Œstrus and Gastrus, or Gastrophilus). To the first-named genus belongs the

Ox Warble-fly, or Ox Bot Fly (Hypoderma bovis),

two-fifths of an inch long, black. Hair: whitish yellow on the head; reddish yellow on the fore part of the thorax, black on the hinder part; grey on the fore part of the abdomen, black in the middle, and reddish yellow behind. Legs black. Wings brownish, not quite transparent.

On the wing during summer (June to September). As soon as the cattle hear the flies buzzing around (especially on hot days) they become very restless, run about as if mad, and even plunge down steep places. Young cattle are selected for egg-laying; the elongated white eggs are fixed separately to hairs. The maggot, elongated when first hatched, perforates the skin, and gets into the subcutaneous connective tissue, where it does not, as a rule, keep to any one place, but wanders here and there, sometimes penetrating the flesh, or even entering the spinal canal. It always, however, wanders back again later on into the subcutaneous connective tissue, where it gives rise, during the winter or the following spring, to one of the well-known tumours, or “warbles.” After fixing on a definite spot, it moults, becoming broader, and of a yellowish white colour. The maggot first causes an increased flow of blood to the part, and then inflammation. An excavation filled with matter is thus developed, and there is gradually formed a connective tissue sac communicating with the exterior by a minute tube. In spring, or early summer, the warble, which is visible externally, has reached the size of a pigeon’s egg; the maggot meanwhile becomes first greyish yellow, then brown patches appear, and lastly it assumes a dark brown colour, is an inch long or rather more, and somewhat swollen. It is now ready to pass into the resting stage, crawls out, and lets itself fall to the ground, where, within the larval skin, it becomes a black pupa four-fifths of an inch long, from which, about four weeks later, the fly creeps out. Damage done: If the warbles occur only in small numbers on an animal, its health is not much affected, though this must undoubtedly be the case if there are many, say fifty, or even up to a hundred, in the same animal. In such cases the yield of milk will be considerably diminished. Holes, too, are present in the skin, which, though they may close again, if the animal remains alive, always leave a thin place. The outer surface of meat from animals infested with warbles is dirty yellow, flaccid, or even soft and jelly-like (“licked beef”); it must be scraped off. Enemies: Starlings settle, in spring, on the backs of infested cattle, and seize the parasites with their beaks. Starlings, rooks, and wagtails destroy the maggots ready to become pupæ, as they lie on the ground. Remedies: Washing the back, shoulders, and loins with vinegar extract of walnut leaves during the summer, to keep away the bot flies. In spring: squeezing out the maggots from the warbles, having previously opened them, when necessary, with a penknife. If the warble is “ripe,” i.e. if it has opened so far that the black hinder end of the maggot can be seen, the opening may be stopped with fat or cart-grease, by which the larva will be killed where it lies.

The Sheep Bot Fly (Œstrus ovis),

two-fifths to three-quarters of an inch long, yellowish grey, almost hairless; head large, round, reddish; thorax grey, with small black warts; abdomen yellowish white; legs short, bright; wings of a glassy clearness. The flies are found (in September) on the walls of sheepfolds, and in woods near which sheep graze. On sunny days the female flies round the sheep, in order to deposit her brood upon them. The sheep threatened press their nostrils to the ground, though this is not of much use. The maggots are hatched while still in the body of their mother, and are deposited by her on the margins of the nostrils. These little maggots creep about on the mucous membrane lining the internal cavities of the nose, causing intolerable itching. The sheep try to get rid of the intruders by shaking their heads and rubbing their noses on the ground. The maggots, however, creep further into the nasal cavities, and get into the hollows of the frontal bone and upper jaw, perhaps even into the horns. In these places they feed on the fluid which their presence causes the mucous membrane to give out in large quantities. The maggots remain as such for nine months, during which time they alter their shape in various ways. Those just born are white, one-twenty-fifth of an inch long, while those which have reached the length of two-fifths of an inch are yellowish white. Individuals ready to become pupæ are about an inch long, yellowish brown, with dark transverse lines; they wander back to the nasal cavities and thence to the exterior, often being expelled by sneezing. In the soil they become pupæ, first of a brown, then of a black colour, within the larval skin; the flies emerge in six or seven weeks. Different maggots develop at different rates, according to the nature of the cavities into which they penetrate.

The maggots cause the disease known as “false gid,” which appears most obviously from March to May; at this time the parasites are tolerably well developed. They irritate the mucous membrane of the cavities of the head in which they live, causing an unusually large flow of blood to these parts, as a result of which the mucus secreted in the nose increases largely in quantity (sneezing, snuffling), and the brain begins to work abnormally (uneasy movements of the head, high lifting of the feet; in worse cases, rolling of the eyes, gnashing of the teeth, and foaming at the mouth). The sheep have also an intolerable itching of the nose, which they rub in consequence on the ground, against posts, or their own legs; besides this, there may be inflammation of the eyelids and increased secretion of tears. They are also apt to grow very thin. The disease is more frequent, and the symptoms severer, in young than in old sheep. False gid may cause death; the animal is cured, however, after the maggots have crept out. Preventive Measures: Keeping the sheep away from the edges of woods, avenues, etc., where the flies live by preference. When sheep are killed, the maggots coming from the head should be collected and destroyed. Smearing the margins of the nostrils with tar, or rubbing them with walnut leaves, before the sheep go to pasture in the morning. For sheep, which in late summer rub their noses up and down tree stems, walls, hedges, or their own legs, substances that cause sneezing may be employed, e.g. cheap snuff, which is best introduced into the nose by means of a quill-feather. Later on, when the maggots have passed from the nasal cavities into the frontal sinuses, etc., sneezing does no good. Operations seldom succeed in removing all the maggots.

The Bot Flies (Gastrus, or Gastrophilus) live in various parts of the stomach (in left side of horse’s stomach) and intestine. I give, first of all, a compressed tabular view of the external characters and mode of life of the four British species. (See next page.)

Diseases caused by Bot Flies.—The maggots bore into the walls of the stomach and intestines until they reach the layer in which the blood-vessels, lacteals, and lymphatics ramify; they then suck the juices found in these vessels, and also serous fluids. In small numbers they are often almost harmless, but when a great many are present they hinder the secretion of the digestive juices. They may also set up inflammation of the intestinal coats, or may cause death by internal bleeding if they perforate the wall of an artery. In foals they often bore right through the wall of the intestine, and enter the abdominal cavity, where they may set up inflammation of the peritoneum or of the mesentery. There may be as many as a hundred or two hundred maggots in the stomach or intestine, and they then cause, at the very least, digestive disturbances and colic. If the maggots (G. nasalis) get into the windpipe (or larynx) they interfere with the breathing; if into the gullet, with swallowing. In either case death may ensue (winter, early spring). Remedies: Killing the flies as they lay their eggs. Removing the eggs by brushing, combing, and washing; the last is best done with warm water, to which some caustic potash is added. Rubbing the lips and nostrils, neck, chest, and fore legs with walnut leaves, or a decoction of the same.

Body flat and broad; skin leathery and tough. Fore legs curved, adapted for climbing among the hairs. Some (e.g. the Forest Fly) have a pair of wings, others (the Sheep Louse Fly) are wingless. They bring forth living maggots, each time one only, which is ready to become a pupa immediately. They reproduce several times. Here belong: 1. The Forest Fly, Spider Fly, or Flat Fly (Hippobosca equina), about one-third of an inch long, brown, with broad abdomen, and two broad stumpy wings. Occurs in summer and early autumn, chiefly on horses, especially near the anus, on the belly, and on the flanks. It sucks blood, and irritates by running about on the body. Seldom flies. 2. The Sheep Louse Fly, wrongly called “sheep louse” and “sheep tick” (Melophagus ovinus); about one-fifth of an inch long, wingless, rusty yellow, with brown abdomen, very hairy. Climb slowly about among the wool of the sheep, and suck blood. Their excrement may colour the wool green. Lambs especially are much hindered in their growth by this fly. The fleece is also damaged, for the itching set up by the insect forces the animal to rub itself against things so that the wool gets pulled out. The flies are chiefly found on meadow sheep; but relatively few in winter. The parasites leave the body of their host for the purpose of reproduction, and lay their maggots, which at the time of birth are nearly one-sixth of an inch long, under little bits of earth or heaps of dung. When sheep are kept in folds no permanent result can consequently be expected from the use of any remedy if, at the same time, the fold and all its contents are not kept clean. The walls must be cleansed, and washed with caustic potash, to which carbolic acid has been added. Curative Washes: A decoction of walnut leaves and vinegar. Turpentine, soapsuds, decoction of tobacco. Washes containing arsenious acid (e.g. Bigg’s Improved Sheep and Lamb Dipping Composition) must be used with caution; unpalatable substances may be added, so that the sheep will not lick them, or else a muzzle may be employed.

Ninth Order: Aphaniptera (Fleas).

Body strongly compressed laterally. Head small. Mouth-parts adapted for sucking and biting. Legs long, especially the last pair. They possess the power of springing. Wingless. Complete metamorphosis. Larva worm-like, legless, hard-headed. The Dog Flea (Pulex serraticeps), which only occasionally passes on to human beings, lives on dogs and cats. Remedy: Sprinkling the moistened hair with Persian insect powder or powdered parsley seed.

Tenth Order: Parasita (Lice).

Body flattened. Legs adapted for climbing among hairs and feathers, as the last joint of the foot is hook-shaped, and can be bent back against the preceding joint; a hair can thus be held fast between the two joints. Eyes absent or ill developed (simple). Wingless. The eggs (“nits”) are fastened by the mother louse to the hairs of the host; the young lice resemble the old ones in almost all particulars; there is no true metamorphosis. All lice have a kind of proboscis, which can be protruded and retracted, and upon which are placed the mouth-parts, which enable it to be used for sucking or biting. According to the last feature a distinction can be drawn between true or blood-sucking lice and biting lice or fur-eaters, which devour small scales derived from the skin or else bits of hair and feathers. Lice multiply very rapidly on the bodies of human beings and animals when insufficiently cleansed, and under these circumstances more on sick and ill-nourished individuals than on those which are healthy and well nourished. It is obvious that the true, blood-sucking lice usually injure their host more than the biting lice, which, however, especially when present in large numbers, may cause an intolerable and injurious itching by their movements here and there. Preventive Measures: Suitable feeding and treatment. Proper care of the skin. Remedies: Repeated combing with a comb which has been dipped into a solution of soda. Rubbing the badly infested spots with soft soap and soda, washing them out after twenty-four hours. Among other washes are—6 parts soft soap, 1 part benzine, 10 to 15 parts water; or tobacco water, 1 part of common tobacco in 20 to 25 parts water; arsenious acid, in various mixtures, e.g. in Bigg’s Composition (p. 193). Employ the muzzle.

Respiration by tracheæ, as in insects. The body consists of a head and a large number of very similar segments, each of which possesses limbs. One pair of antennæ.

This class is divided into two orders: (1) that of Centipedes (Chilopoda), with mouth-parts adapted for seizing prey, and one pair of legs to each segment; (2) that of Millipedes (Chilognatha), adapted for devouring substances resembling humus, also the parts of plants; and two pairs of legs to each segment. Here belong, above all, the Snake Millipedes (Julus) or “False Wireworms” (Fig. 123), of which several species eat out germinating seeds (peas, beans, mangolds, and beet), and also attack juicy plant parts (potatoes, turnips, carrots). Seedlings may be protected by using potatoes to draw away the millipedes.

CLASS III.: ARACHNOIDEA (SCORPIONS, SPIDERS, MITES).

Air-breathing (by ordinary or modified tracheæ); the lower forms breathe with the skin. Body at most consists of two chief regions, since head and thorax are always fused together, making up a cephalothorax (Fig. 124); but this may again be united with the always unsegmented abdomen into a single piece (Fig. 127). The last is the case with the mites, in which, therefore, the characters of segmented animals can only be recognized in the limbs. In the true spiders (Fig. 124) the body consists of cephalothorax and abdomen. Arachnids have always four pairs of legs, which, in the true spiders, are attached to the cephalothorax, in the mites to the front part of the unsegmented body.

The chief Orders belonging here are: (1) true Spiders (Araneida); (2) Scorpions (Scorpionida); (3) Harvestmen (Opilionida); (4) Mites (Acaridea). Only the last contains species of importance agriculturally.

Order: Acaridea (Mites).

Small arachnids, in which the cephalothorax and abdomen are fused together into one piece (Fig. 127). The just-hatched young have three pairs of legs, the adults, of course, four.

Family: Acaridæ (True Mites).

Soft skin. No tracheæ, no eyes. Legs short, often with a sucker at the end. Here belong the Cheese Mite (Acarus siro), the Meal Mite (Tyroglyphus farinæ), and several other species living in dead organic substances; also—

The Itch, or Mange Mites.

These live as parasites on or in the epidermis, and cause the itch or mange (scabies) in man, as well as in several domestic animals. By means of the structure and habits three genera are distinguished:—

1. Digging, blood-sucking mange-mites living in the skin (Sarcoptes);

2. Blood-sucking mange-mites living on the outer surface (Dermatocoptes);

3. Mange-mites which merely devour scales of the epidermis (Dermatophagus).

It is obvious that sarcoptic scabies is not so easily cured in the same host as the dermatocoptic scabies, since the mites causing the former dig their passages into the epidermis, while those causing the latter at least remain on the surface. Dermatophagic scabies is most easily got rid of, since the mites which cause it not only remain on the outer surface of the skin, but also, instead of holding fast, run about here and there; it is easily understood that this kind of mange can often be removed by simple brushing.

The itch, or mange (scabies), is caused by the irritation which the mites continually exert on the skin. The warmer the surroundings of the host, the more active the mites, and the more painful the skin disease. (The scarcoptes mites, e.g., are most unendurable in man when in bed, and scabby sheep are most tormented when in a warm fold.) The mites multiply with such enormous rapidity that it is easy to understand how a single fertilized female, transferred to a new host by contact with an affected animal, is able, in a short time, to make large patches of the skin mangy. The course of the disease is generally as follows:—Soon after infection small swellings appear, which become little bladders of the size of a pin’s head. These burst, and the affected parts of the skin are quickly covered with a crust formed from shrivelled bits of skin and dried-up fluid. In many places the attacked parts of the skin are moist, for the host, in consequence of the severe itching, rubs or knocks itself. In consequence of the shedding of fluid the hairs stick together, and later on fall out. The skin thickens, becomes encrusted, and is thrown into folds, between which there are deep cracks. Among domesticated animals the sheep is certainly the one which suffers most from scabies (Dermatocoptes), especially as the disease spreads rapidly in the warm sheltering fleece, which also makes the removal of the parasites a matter of the greatest difficulty. The wool gets dry and brittle in the diseased parts, and its fibres become loose, though they remain attached for a short time, since their tips are glued together by the sticky substance which exudes from the little thickenings in the skin. They gradually fall out, however, leaving the skin covered with a thick brownish crust, looking as if it were soaked with oil. Badly infested sheep get thin and even die. This, however, is not usually the case, and the injury consists in the great deterioration of the wool, both as regards quantity and quality.

The following summarizes the kinds of scabies affecting man and domestic animals, and indicates how far one kind of host can affect another:—

Itch of Man (Sarcoptes) can be caught by the dog, but by no other domestic animal.

Scabies of the Horse.—The sarcoptes mange of this animal is contagious for man, and for the ox, but no other domestic animal. The dermatocoptes mange (found more particularly on the inner sides of the legs, and on the genital organs, tail, and mane) does not spread to man or to other domestic animals. Nor is this the case with the dermatophagus mange of the horse (on the fetlocks and adjacent parts of the legs).

Scabies of the Ox.—The dermatocoptes mange of the ox (chiefly affecting the sides of the neck and root of the tail) spreads to men and horses, but not to sheep. The dermatophagus mange (principally on the root of the tail and near the anus) does not seem to be transmitted to man, horse, pig, or dog.

Scabies of the Sheep.—The dermatocoptes mange of sheep is not transmitted as a permanent disease to man, nor to other domestic animals (with the exception of the goat). The sarcoptes mange of the sheep (chiefly on the head) causes the itch in man.

Scabies of the Pig (Sarcoptes) is contagious for the dog, and causes an eruption in man.

Scabies of the Dog (Sarcoptes) can be caught by man, pig, and horse.

Scabies of the Cat (Sarcoptes) is contagious for man, horse, ox, dog, and rabbit.

Scabies of the Rabbit (Sarcoptes) is contagious for man, but this is not so with the dermatocoptes mange, which flourishes in the external passage of the ear in the rabbit.

Scabies of the Fowl (Sarcoptes), which affects the legs of hens, causing thickening of the skin and formation of large spongy crusts, may infect horses. Hen-houses should not be built in stables.

Remedies.—From the foregoing facts relating to the transmission of scabies from one host to another, the preventive measures at once follow: A mangy animal must not be allowed to come into contact either with another animal of the same kind or with an animal of any other kind for which the disease in question is contagious. If scabies appears in a few members of a flock or herd, it is absolutely necessary to separate the healthy animals from the sick ones,—and it is further necessary to cleanse and disinfect places where mangy animals have been kept, as well as implements or machines which they have touched, before sound animals are brought near such things. Cleansing of folds, etc., with hot water, followed by six weeks’ disuse. Cleansing of infected implements with hot soda and water. The first important thing to ascertain is whether a sick animal, which has the external symptoms of scabies, is really affected; in order to determine this the mange-mites must be found. If the mites cannot be found on the suspected animal, it must be brought into a warm stall and covered over; especial care must be taken to warm the places where the skin seems worst attacked; warmth makes the mites more active, and induces them to come to the surface. Sarcoptic mites are the worst. I will deal but briefly with the treatment of mangy animals, as it is usually best to obtain the advice of a veterinary surgeon. External applications must naturally be employed. It appears from the investigations of Vogel that corrosive sublimate and arsenic kill the mange-mites less rapidly and therefore less surely than creosote, carbolic acid, benzine, tar, caustic potash, and tobacco, or even soft soap. Zürn recommends a thorough smearing of soft soap on the parts affected. The soap is allowed to remain for some time, even for a whole day, the infested spots are then rubbed with hot water, and brushed, if possible, until the crust on the skin disappears. Other remedies may now be employed. As such, Zürn mentions creosote, diluted with spirit or oil (1 : 25). Also, among other things, the following are recommended—benzine shaken up with water (1 : 5–10), or a solution of 1 part caustic potash in 30 to 40 parts of water. The above and several other remedies can be used with good results in combating scabies in most of our domestic animals. But there is more difficulty with sheep than with other animals, for the fleece is a hindrance to the beneficial action of the wash employed. It is not possible to make the sheep quite healthy so long as they remain unshorn. Till then, the efforts made must be directed to preventing the spread of the mange. This is managed in the following way. The crust is scraped from the parts attacked, after the loose wool which covers them has been removed. The mangy places are then rubbed with a decoction of tobacco leaves with carbolic acid (1 part carbolic acid to 15 parts spirit and 60 parts water), or with some other of the remedies named above. When the sheep are shorn, first dip them in a solution (2 parts soda, 1 part lime, and 50 parts water) by which the crust on the affected places is softened; twenty-four hours later dip in a solution which will kill the mites. A decoction of tobacco (1 part tobacco to 12 parts water) may be used for this purpose, using for each sheep about 1¾ pints of the fluid, to which has been added 6½ drams carbolic acid and 6½ drams alcohol. The first washing must be followed by a second, for the fluid destroys only the mites and not their eggs. As the young mites are hatched out in three to seven days, the dipping must be repeated seven days afterwards.

Family: Ixodidæ (Ticks).

Ticks are generally rather larger than the mites of the preceding family. The skin is tough as leather. The front part of the body is covered by a hard shield above; the skin of the hinder part, though tough, is very extensible. The front end bears a sucking apparatus formed by the pointed jaws, and by its means the tick pierces the skin of man or animals and holds on fast. Ticks are chiefly found in sandy soil, among bushes and shrubs, or among herbs. As long as they remain on the ground they are tolerably small (⅒ inch) and very active. They creep up haulms and branches, and rest in a suitable spot till a mammal or bird passes, when they attach themselves to its hair or feathers by their legs, and bore into its skin with their sharp mouth-parts. Having thus fixed themselves, they suck the blood of their temporary host. The walls of their stomach and intestine are extremely elastic, so that the tick, which at first is only about one-tenth of an inch long and one-sixteenth of an inch broad, becomes as big as a pea, or even a garden bean. When the tick has sucked itself as full as possible, it withdraws its mouth-parts from the skin of its host for the time being, and lets itself fall to the ground, where it lies for many weeks without feeding. The small and feeble legs of the tick are not able to move the heavy, blood-filled body, and movements do not take place for some time, till the greater part of the imbibed blood has been digested and the tick has shrunk once more to its normal size. What has been said about the habits refers only to the female; the much smaller male never seems to pierce mammals, and its food is not known. In pairing, it is found attached to the under side of the female, remaining there several days, even when the female is fixed to the host. Egg-laying does not take place till the host is quitted. As ticks draw blood from their host their presence, in spite of the fact that they remain but a short time, is not a matter of indifference, especially if large numbers affix themselves to one animal. Sheep and cattle become thin if daily attacked in the meadows by many ticks. The piercing of the skin causes a stinging sensation, followed later on by itching of the parts to which the ticks are attached. The ticks which are fixed must never be seized and pulled out, for the mouth-parts are so deeply imbedded in the skin that it is impossible to remove them by force, and the attempt would only result in tearing the body from the mouth-parts. A better plan is to put a drop of oil or tobacco water, or, still better, benzine, on the tick, when it will loosen itself. We distinguish between the Dog Tick (Ixodes ricinus), the Sheep Tick (I. reduvius), and the Ox Tick (I. reticulatus), which, however, are not found exclusively on the animals after which they are named. The first, although found most commonly on the dog, attacks men who force their way through underwood (hunters), and in the same way fixes on sheep and oxen. The last two species are chiefly, but not exclusively, found on sheep and goats.

Family: Gamasidæ (Beetle Mites).

Beetle mites are temporary parasites on insects, reptiles, and birds. They have no eyes, but possess shear-like jaws, and tolerably long hairy legs. The Beetle Louse (Gamasus coleoptratorum) lives on dung beetles, sexton beetles, etc.

The Fowl Mite (Dermanyssus gallinæ) is the size of a sand grain, and blood-red or red-brown in colour. During the night it is found in large numbers on the fowls, but during the day hides on the perches, in the nests, and particularly in the chinks and crannies in the walls of the poultry-house, also in dung. It draws much blood from the fowls, and disturbs their sleep by producing a constant itching, the result being that they get very thin. Remedy: Whitewash the fowl-houses twice a year (autumn and spring) with hot lime to which 5 per cent. of carbolic acid has been added. The wooden parts should be scalded with boiling water before whitewashing.

Body four-cornered or longish oval; legs tolerably long, hairy; jaws claw or needle-shaped; surface of the skin velvety; colour reddish or yellowish. They run about with great rapidity on the ground, tree trunks, leaves, etc. Most species feed on the juices which they suck from insects, or from other arachnids.

The Plant Mite, or Red “Spider” (Tetranychus telarius),

is ovoid, at most one-fiftieth of an inch long; reddish (also yellowish or brownish), with a dark spot on each shoulder. Plant mites are often found in considerable numbers during the summer, especially on the under sides of the leaves of low-growing plants; on garden beans, turnips, and hops; on several ornamental plants, grasses, and various weeds; on roses, limes, horse-chestnut trees, elms, willows, and fruit trees. In some exceptionally dry summers the mite increases to such an extent as to become a great pest. On the upper sides of the infested leaves there is to be seen, besides the adult and immature mites, a whitish, mealy substance, consisting of the cast skins and whitish eggs. Many of the mites run about here and there, but most of them remain fixed, and suck the sap. All are covered by a delicate web, which is formed by the animal. The attacked leaves become limp, shrivel up, die, and fall off. In dicotyledonous plants the withering generally commences in the axils of the veins. The infested plants often die off gradually, but death may also take place with great rapidity. Annuals are often killed by the attacks of the mite. The mites pass the winter in the ground, under fallen leaves, under the bark of trees, etc.

The Crustacea breathe by gills, and are therefore suited to an aquatic life. A few species, however, live in damp earth, or in places where the air is damp (wood lice). Crustacea have two pairs of antennæ, and a large number of appendages arranged in a characteristic way, but differing very much in shape in the different groups; skin usually hard and thick. Lobsters, crayfish, crabs, wood lice, and the small sand-hoppers, water-fleas, etc., belong to the Crustacea. No Crustacean is harmful agriculturally.