Chapter VI: Part 6

Male ¹⁄₂₅ inch, female (Fig. 110) ¹⁄₁₇ inch, and possessing an ovipositor which, when extended, is twice that length. Citron yellow, slightly hairy; antennæ blackish, eyes black, legs dirty yellow. In spring or early summer, the midges creep out of the soil in fields where wheat has been planted the previous year. After pairing, the females wander to fields where wheat or, more rarely, rye is growing. The attacks of the midges commence when the ears begin to emerge from the leaf-sheaths, and are continued throughout the flowering time of the wheat. At night the female pierces the glumes with her ovipositor, and lays three to ten perfectly transparent eggs in each flower. Each midge lays eggs in several flowers, but two or more midges may use the same flower for this purpose, so that as many as thirty maggots may be found in one bloom (Fig. 112). The maggots, which are hatched out in a week, creep down to the ovary and suck its juices. If many maggots live in one flower it is sure to die, but if there are only a few it may produce a grain, though this may be small. Ears infested by the maggots develop yellow spots later on; many ears remain quite empty, and consequently thin and upright. Full-grown maggot: ⅛ inch; straw yellow to chrome yellow; quite transparent when very young. Is fully developed in three weeks, and then lets itself fall to the ground (July or August). Becomes a pupa the following spring; fourteen days later the midge escapes.

Family: =Rostratæ= (_Crane Flies_, _Daddy Longlegs_).

FIG. 113.—The Daddy Longlegs, or Common Crane Fly (_Tipula oleracea_).
Left, the male and the maggot; right, the female and the pupa.
]

These very long-legged gnats live on the juices of plants, and do not sting. The larvæ are legless, without a hard well-marked head; those of most species live in mouldering plant parts (_e.g._ rotten wood), or the decaying manures of our fields and meadows. A few species, however, are very destructive, since they injure roots and other parts of cultivated plants. The adult and larval stages of all the injurious kinds are not yet distinguished. We know that the larvæ of the yellow and spotted _Tipula maculosa_ are chiefly destructive in sandy soil; while more binding clay soil and rich garden earth are infested by the larvæ of _Tipula oleracea_ (Fig. 113), and damp meadows by those of _Tipula paludosa_. The two last-named species are very much like one another; grey or greyish brown with bright brown wings, having dark front margin. Much is still unknown about the habits of “crane flies”; my researches relate to the =Yellow-spotted Crane Fly= (_Tipula maculosa_). The adults fly about in swarms during summer, usually from the beginning of June, in the fields where the larvæ lived in spring. They lay their eggs either in the same fields or (usually) in others, and are blown about for long distances by the wind. Where the flies settle they lay each time two or three black ovoid eggs, bent like a sickle, and repeat this till all the eggs (200 to 250) are laid. Those fields which have previously been grass land are the most infested by the crane flies. The larvæ are headless, grey to lead coloured, with small prickles at the hinder end of the body, and they first appear, in large numbers, under the pieces of turf which are left behind in such fields, and which appear to be the centres from which the destruction of the standing corn begins. The larvæ are hatched out in summer, during the later part of which, and during autumn, they devour plant roots; after hybernating, they again attack the underground parts of plants the following spring. They devour most readily the roots of grass and corn, but also those of clover, rape, and several other plants, including some found in flower and kitchen gardens. They are mainly injurious either in autumn or spring, according to the nature of the plants attacked. Young grain-plants are killed by them, older ones usually not. On fields where winter corn grows they therefore do most damage in autumn, while this is the case in spring on land where summer corn is cultivated. They are sometimes harmless, since they can also feed on roots left behind in the ground. The larva do not limit their ravages to underground parts; in the evening, and also in the daytime during dark damp weather, they devour parts of the first leaves of very young corn plants, though the damage thus effected is often inconsiderable. In May the larva is ready to pass into the pupa stage; it comes near the surface and becomes a brown pupa, bearing small spines on the abdominal rings. After a rest of fourteen to seventeen days, the pupa works its way upward till the front part of its body sticks out of the soil. The fly then escapes. _Enemies_: Mole, shrews, wagtails, grasshopper warbler, rook, gulls. _Remedies_: When the maggots are very destructive in gardens they may be collected, preferably in wet weather, since they then leave the soil during the day. If they appear to an injurious extent on summer corn, the fields should be rolled in April (either with the ordinary or the spiked roller). At the time (June) when the crane flies swarm about the fields and meadows in flocks, thousands of individuals can easily be caught with a net.

Family: =Muscæformes= (_Gnat Flies_).

Gnats with relatively short legs, and antennæ which are in any case shorter than the body, and are usually quite short and cylindrical, possessing, however, six or more joints, while the antennæ of true flies usually have only three joints. The gnat flies form, as it were, the transition between the slender gnats with their long legs and antennæ, and the more thick-set flies, the legs and antennæ of which are short. Here belong the genera of =Shade Gnats= (_Sciara_, e.g. _Sciara Thomæ_, the larvæ of which often wander about in companies, as the so-called =Army Worm=), the =Sand Flies= (_Simulia_), and the =Hair Gnats= (_Bibio_, _e.g._ the =Garden Hair Gnat=, _Bibio hortulanus_, the larva of which gnaws the roots of plants, especially in humous garden soil).

The =Sand Flies=, or =Mosquitoes= (_Simulia_),

have thick-set bodies, short legs, and short nine or ten-jointed antennæ; they are from ¹⁄₂₅ to ⅕ of an inch long, and have a short but sharp proboscis, with which they suck up the flower juices which constitute their chief food. But the female also sucks the blood of human beings and animals, making herself exceedingly annoying in this way. Its larval state is passed through in stagnant water; its appearance is therefore local, and is especially favoured by damp summers. The mature sand flies are found from early spring or through the whole summer; several generations succeed one another in the same year. Sand flies often appear in swarms, containing thousands of individuals. Since the female eagerly creeps into the ears, noses, and corners of the eyes in horses and oxen, she is extremely annoying and even dangerous. Her bite produces a smarting sensation, and may cause actual boils to form in the skin. When a large swarm of sand flies settles on a herd of cattle or on some horses, these animals become maddened and furious; they often rush wildly round for so long that they fall down dead. _Simulia reptans_ is a common British form. _Remedies_: Compare what is said on p. 165, about gnats. Sand flies can usually be kept from horses’ ears by means of ear-caps.

Family: =Tabanidæ= (_Gad Flies_).

FIG. 114.—The Rain Breeze Fly (_Hæmatopota pluvialis_).
]

Large or medium-sized flies with thick-set body, large broad head, flat abdomen, and strong legs. The proboscis is less developed in the male, which lives merely on plant juices, than in the blood-sucking female. The cylindrical whitish larvæ live in earth, and are harmless. But the female insects bite human beings, and the larger kind attack horses and cattle in such a manner that blood-drops may be seen on the ground under the animals attacked, if these remain for a time in the same spot. There belong to this family: 1. The =Breeze Flies= (_Tabanus_), large insects up to ⅘ inch long, which are seen flying about with a buzzing sound over meadows and fields in the sunshine (=Ox Fly= = _T. bovinus_; =Horse Fly= = _T. autumnalis_). 2. The =Lesser Breeze Flies= (_Hæmatopota_), smaller and more slender, with grey wings, bite most before a storm and in hot sultry days. 3. The =Blinding Breeze Flies= (_Chrysops_), as large as the Lesser Breeze Flies, but broader, with shining golden-green eyes and wings marked with black. _Remedies_: Compare p. 165, and above; draining the soil, however, is no good here.

Family: =Muscidæ= (_True Flies_).

These are flies with three-jointed antennæ, constructed on the type seen in the common house fly. Here are included the =Caterpillar Flies= (_Tachina_), the =Flesh Flies= (_Sarcophaga_), =Common Flies= (_Musca_), =Flower Flies= (_Anthomyia_), =Green-eyed Flies= (_Chlorops_), etc.

The =Caterpillar Flies= (_Tachina_)

are black, grey, or reddish yellow flies, reminding one by their appearance of the common house fly or the blue-bottle. They play the same part in the economy of nature as the sand wasps (p. 129), but always lay their eggs externally on the skin of the host; the maggots consequently never prey on those insect larvæ which live in the tissues of plants or in the soil.

FIG. 115.—Caterpillar Fly (_Tachina fera_).
]

The =Flesh Flies= (_Sarcophaga_)

have a longish abdomen, with large bristles on the hinder margins of the segments. Thorax with three longitudinal streaks. The flies suck up sweat, but do not bite. The eggs develop within the abdomen of the mother; the flies lay the young larvæ in dead flesh; also, if not kept clean, in wounds of human beings and animals,—sometimes, too, in the genital opening of horses, cattle, and swine, in which case the maggots live as true parasites in the vagina and uterus, causing a secretion of mucus, upon which they live. Two to three generations yearly; fifty to eighty maggots each time. _Remedies_: On keeping the flies from cattle, cf. p. 165; to keep them from meat, flynets, a gauze cover. =Blow Fly= (_S. carnaria_), with black speckled abdomen.

The =Common Flies= (_Musca_)

are coloured dark or shining green. The headless white maggots live in dung (=House Fly= = _Musca domestica_), in fresh or decaying meat (=Blue-bottle= = _M. vomitoria_), exceptionally (_M. vomitoria_) in wounds that are not kept clean, or in the vagina of several domestic animals. _Remedy_: Compare above (“Flesh Fly”).

The =Flower Flies= (_Anthomyia_).

These are found on flowers, and resemble many common flies in appearance and colour. The headless white maggots live in dung, also in decaying or sound parts of plants; a few species may sometimes develop in the one kind of material, sometimes in the other. _Anthomyia meteorica_ swarms round the heads of domestic animals, and may even cause inflammation of the eyes and ears. The =Wheat Bulb Fly= (_Anthomyia coarctata_, about a quarter of an inch long, yellowish grey, with black hairs) lives as a larva during winter and spring in the hearts of rye and wheat plants, the leaves of which become yellow in consequence. During April and the beginning of May the larvæ quit these plants and become pupæ in the ground. The second generation can, in like manner, live in various kinds of summer grain. The =Lupine Fly= (_A. funesta_)—nearly one-fifth of an inch long, brownish grey (male) or whitish grey (female), with black legs—digs, when a larva, tunnels in the roots, stems, and seed-leaves of young lupine plants, causing the root and stem to turn black, and the seed-leaves to wither. _Preventive Measure_: Early sowing of the lupines. The =Mangold and Beet Fly= (_A. betæ_), a quarter of an inch long, yellowish grey, lays its eggs, five to eight in number, in the young leaves of mangold and beet. The maggots devour the green substance of the leaf between the two layers of epidermis, so that the leaves die. In June the maggots creep out of the leaves, and become pupæ in the soil. The flies quickly escape, and two or three generations follow one another in the year. As, however, the leaves are now larger, the later generations only effect a small amount of damage. _Preventive Measure_: Close sowing of the turnips, so that even if many are killed there will still be enough young plants. The =Cabbage Root-eating Fly= (_A. radicum_) and the =Radish Fly= (_A. floralis_) live as fleshy, wrinkled, dirty white maggots with black dots, in the underground parts of turnip, cabbage, horseradish, radishes, etc. They lead a similar life to the =Cabbage Fly= (_A. brassicæ_), the cylindrical, smooth, yellowish white maggot of which lives in the underground parts of cabbage, turnip, and rape. The roots attacked swell here and there (Fig. 116), and later on decay; the leaves of the infested plants first become of a dull leaden colour and then wither. Entire fields of cabbage, rape, or turnips, are often destroyed by cabbage fly maggots. The insect passes the winter in the pupa state; the flies appear early in the spring, and usually twice more later on. It is therefore most desirable to pull up and burn the infested plants as soon as possible. A proper rotation of crops should also be practised. [The =Onion Fly= (_A. ceparum_) maggot feeds within the bulbs of stored onions. The male fly is grey, the female yellow.]

FIG. 116.—A turnip infested by the Cabbage Fly: A, swellings; G,
tunnels.
]

The =Cheese Fly= (_Piophila casei_),

one-fifth of an inch long, slender, with a metallic sheen, almost hairless, black, with dirty yellow legs and wings of glassy clearness. These small flies abound in front of the windows of places where cheese is stored; in summer and autumn the shining white maggots, which are cylindrical in form with tapering ends, and one-third of an inch long, live in large numbers in old cheese, gnawing it through and through, and making it dirty. Now and then they spring forwards by bending their bodies into a circle and suddenly straightening them again. They become pupæ on the walls or in straw, near the cheeses from which they have crept out. _Remedies_: Keeping the cheeses clean; mechanical exclusion (gauze screens outside the windows, enclosure in chests).

The =Green-eyed Flies= (_Chlorops_)

include a number of small flies, under one-sixth of an inch long, with spherical head, rounded greenish eyes, strongly arched thorax, and short egg-shaped abdomen, pointed in the male and blunt in the female. The headless larvæ live in the haulms of grasses and species of grain; the life history of a few forms only is adequately known. A few are harmful, especially as there are two or three generations annually. The late summer generation often appears in large numbers, indeed in actual swarms. Since no species lives exclusively on corn, it is impossible to keep them down for a long period of time. I describe only two species:—

FIG. 117.—The Ribbon-footed Corn Fly (_Chlorops tæniopus_).
]

The =Ribbon-footed Corn Fly= or =Yellow Haulm Fly= (_Chlorops tæniopus_), nearly one-sixth of an inch long, shining yellow; the antennæ are black, and there are three longitudinal stripes on the dorsal side of the thorax and four transverse bands on the abdomen of the same colour; the latter region is scarcely longer than the thorax. The insect (Fig. 117) is on the wing in cornfields about the middle of May. It lays its eggs separately on the upper leaves of various species of wheat, rye, and barley, choosing the upper side of the blade, not far from the sheath. Only those plants are selected for the purpose in which the ears are still hidden deep down between the leaf-sheaths. Wheat plants are picked out whenever possible. The maggot when hatched works its way between leaf-sheath and haulm, digging into the latter. It is yellowish white, clear and translucent, and about a quarter of an inch long. While still young it penetrates the haulm, and then attacks the developing ear or the upper part of the haulm which immediately adjoins this, and travels gradually up to the first node of the haulm or nearly so, always continuing to slowly suck. Thus a furrow, from 2½ to 3½ inches long (Fig. 118, C and D), is formed along the surface of the upper part of the haulm, and often also along the lower part of the ear. The part of the haulm attacked swells transversely, and the part below often remains short, so that the ear cannot emerge from the leaf-sheath; but, in any case, only small worthless grains are developed. The furrow is always much deeper below than above, and its margins thicken in consequence of the swelling of the tissues of the haulm. At the end of June or in July, the larva becomes a pupa at the lower end of the furrow. The yellowish-brown pupa (Fig. 118, B), one-fifth of an inch long, remains as such in the furrow for three weeks; the fly emerges in August. Very considerable damage may be done by the first generation, of which the habits have just been described. During 1869 in Silesia, from two-thirds to five-sixths of the ears in many fields remained hidden in the leaf-sheaths, and consequently gave no increase. The first generation of the ribbon-footed corn fly can also develop in the way described in the haulms of several grasses, _e.g._ in species of _Poa_ and _Holcus_.

The flies, emerging in late summer, lay their eggs, here, too, separately, on the leaves of grass or corn. Wherever possible, they seek out for the purpose the winter wheat plants then present in the fields, but also content themselves with rye, or even with wild or meadow grasses; they have to be satisfied with grasses if, at the time of egg-laying, the winter corn is not yet up. The maggot, when hatched, works its way to the inner side of the leaf-sheath, and thence to the apex of the still very small haulm; there it remains during the winter. The damage becomes apparent the following spring. The growth in length of the haulm in question is extremely small, while growth in thickness increases to an abnormal extent. Almost all the leaves completely surround the haulm, which swells to an enormous extent (Fig. 119), together with the enclosing leaf-sheaths, which are much broader than usual. The unattacked plants are naturally much larger than the sickly ones, and deprive these of air and light, so that they die down, being overshadowed, not only by the sound haulms, but also by their own secondary shoots. The resulting damage may be tolerably great, especially at the edges of the field. It may happen that both summer and winter generations of the ribbon-footed corn fly are harmful in the same district; but it frequently happens that only one or the other is complained of in a particular spot. It is only natural that the flies, which swarm around in May, and again in August, September, or October, should not always find suitable corn plants upon which to deposit their eggs. In such cases grasses are used. _Remedies_: Sowing the summer corn as early as possible, that it may be developed to a stage which is unsuitable for the purpose of egg-laying, before the flies appear. The winter seed, however, must be sown as late as possible, so that the second generation of flies may find no corn plants fit to lay their eggs upon. Bearded wheat, especially the strongest varieties, should be sown in preference to awnless wheat. Careful tillage and suitable manuring, so that strong plants of rapid growth may be produced.

FIG. 118.—The Ribbon-footed Corn Fly (_Chlorops tæniopus_); larva (A)
and pupa (B) magnified. To the left a wheat haulm and ear (C) with
the furrow (_q_) dug out by the larva; the pupa (_p_) is seen at the
bottom of the furrow. To the right a wheat haulm with furrow (D) and
the larva (_r_) lying in it.
]

FIG. 119.—A wheat plant distorted by
the winter generation of the Ribbon-footed
Corn Fly.
]

The =Frit Fly= (_Chlorops_, or _Oscinis frit_)

(Fig. 120, C) is about one-tenth of an inch long, shining black, with a metallic sheen. Legs short, feet yellow. Maggot (Fig. 120, A) yellowish white, about one-eighth of an inch long, cylindrical, and tapering in front. Usually three generations. 1. The maggots of the first generation are found during May, in the lower part of the haulm of summer corn (especially oats and barley); the plants attacked either die off entirely, or some haulms develop further, remaining small, however, and yielding only a few light grains. The base of the haulm thickens abnormally, but the growth in length is always small; the leaves, too, grow badly, first becoming yellowish at the tip, and then entirely yellow or reddish. The symptoms of disease are exhibited to a less or greater extent, according as few or many (even up to ten) maggots inhabit the base of a plant. The shining brown pupæ (Fig. 120, B) are found in the lower part of the haulm, or between the leaf-sheath and the haulm (Fig. 120, D). The adult insect is on the wing at the end of May and in June. The first generation often appear on wild or meadow grasses, and are chiefly seen on summer corn when this is sown late or develops slowly. 2. The maggots of the second generation are found in average cases during July, on the as yet scarcely ripe grains of late summer corn, principally those of oats and barley, often occurring also in the haulms of grasses. They keep between the awns, and suck the juices of the soft developing grains, which are rendered incapable of growth, and in any case remain light. The maggots of the second generation develop more quickly than those of the first or third; they are mature in three weeks. The pupa rest is very short, and the flies appear in August, September, or October. They lay their eggs on the leaves of winter corn or winter grasses, and from these eggs are developed (3) the maggots of the third generation, which are to be found, during September and October, in the heart of winter corn and grasses, injuring these plants in exactly the same way that the maggots of the first generation injure the summer corn. The insect passes the winter as a pupa in winter corn plants or grasses. It is but very rarely that all _three_ generations infest the corn of any particular region; as a rule, only the first, second, or third generations do this, or the first _and_ third; in such cases the other generations live on grasses. _Remedies_: Extermination of the insect is impossible, since it can always go from corn to grass plants. Oats and barley are almost always attacked in spring, if in the immediate neighbourhood there is winter rye inhabited by the maggots, for the flies, when they emerge the next spring, seek out the summer corn. This may, however, be made impossible, or at least difficult, if a field of peas, clover, lupines, rape, or some other crop not of gramineous nature, is interposed between fields of winter corn and those of oats, barley, or similar late sown crops of summer corn. Sowing the summer corn (especially oats and barley) as early as possible.

FIG. 120.—The Frit Fly (_Oscinis frit_, L.): A, larva; B, pupa; C,
fly; D, a diseased corn plant, as appearing in spring,—the larvæ and
pupæ are seen of the natural size in the lower part of the plant.
]

Family: =Syrphidæ= (_Hover_ or _Hawk Flies_).

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.

FIG. 121.—Horse Bot Fly (_Gastrus equi_): _a_, egg on a hair, strongly
magnified; _c_, younger (magnified), and _b_, older larva; _d_,
opened pupa case; _e_, fly.
]

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.

────────────────────┬──────────────────┬──────────────────┬──────────────────
SPECIES. │ FLY. │ EGG. │ MAGGOT.
────────────────────┼──────────────────┼──────────────────┼──────────────────
=Horse Bot= │½ to ⅖ inch, very │White: on the │At first flesh
(_Gastrus equi_). │ hairy, like a │ hairs of the │ red, then
│ humblebee; │ mane, neck, │ yellowish-brown.
│ brownish yellow.│ chest, fore │ Lives in the
│ Fore part of │ legs, and hind │ stomach of the
│ thorax with │ feet of horse. │ horse, often in
│ yellowish-brown,│ │ large numbers.
│ hind half with │ │
│ black hairs. │ │
│ Abdomen with │ │
│ brown hair in │ │
│ front, │ │
│ brownish-yellow │ │
│ behind. │ │
=Cattle Bot= │Male about ½ inch,│Black: on the same│First yellowish
(_Gastrus_ │ brown, closely │ parts of the │ grey, then
_pecorum_.) │ covered with a │ horse’s body as │ blood-red. First
│ mixture of │ in the preceding│ in the small
│ yellowish and │ species; │ intestine, and,
│ black hairs. │ exceptionally on│ for some time
│ Wings │ the hairs of │ during June or
│ smoke-coloured. │ horned stock. │ July, in the
│ Female rather │ │ rectum of the
│ larger. Head, │ │ horse. When
│ thorax, and │ │ ready to become
│ first segment of│ │ pupæ, they creep
│ the abdomen with│ │ out of the anus,
│ colour and hairs│ │ to the margin of
│ as in the male; │ │ which, however,
│ rest of abdomen │ │ they may remain
│ black, and │ │ sticking for
│ tapering │ │ some time.
│ posteriorly. │ │
│ Wings │ │
│ smoke-coloured. │ │
=Red-tailed= =Bot= │About ⅖ inch. Fore│Black: on the lips│First red, then
(_Gastrus_ │ part of thorax │ and margins of │ bluish-green. To
_hæmorrhoidalis_).│ dark fawn │ the nostrils in │ begin with, in
│ colour, with │ the horse. │ the cavities of
│ bright yellow │ │ the nose or
│ fur-like hair; │ │ mouth, in the
│ hinder part │ │ horse, very soon
│ black. Abdomen │ │ in the stomach
│ shining black, │ │ or small
│ with yellowish │ │ intestine,
│ white hair in │ │ remaining there
│ front, black in │ │ several months;
│ the middle, and │ │ then, a few
│ orange yellow at│ │ months longer,
│ the tip. Wings │ │ in the rectum.
│ of glassy │ │ Exceptionally,
│ clearness, with │ │ the maggots
│ dark brown │ │ remain in the
│ veins. │ │ gullet for some
│ │ │ time.
=Nose Bot= │Nearly ½ inch (not│White: on the lips│Yellowish white.
(_Gastrus_ │ including the │ and margins of │ In the first
_nasalus_). │ long ovipositor │ the nostrils in │ part of the
│ of the female). │ the horse. │ horse’s small
│ A fine but close│ │ intestine, near
│ covering of │ │ the aperture of
│ hairs; │ │ the stomach;
│ variegated, not │ │ exceptionally in
│ always evenly │ │ the nasal
│ covered with │ │ cavities,
│ hair, especially│ │ gullet, and
│ not on the black│ │ stomach.
│ abdomen (partly │ │
│ white, black, │ │
│ orange yellow, │ │
│ yellowish grey);│ │
│ thorax a shining│ │
│ blackish brown, │ │
│ covered with │ │
│ fine, golden │ │
│ yellow hair. │ │
│ Wings clear as │ │
│ glass, widely │ │
│ spread when at │ │
│ rest. │ │
────────────────────┴──────────────────┴──────────────────┴──────────────────

Family: =Pupipara= (_Louse Flies_).

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.

FIG. 122.—Horse Louse (_Hæmatopinus macrocephalus_), magnified ten
times.
]

CLASS II.: =MYRIOPODA= (CENTIPEDES AND MILLIPEDES).

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.

FIG. 123.—Common Snake Millipede (_Julus terrestris_), somewhat
magnified.
]

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.

FIG. 124.—A Spider (_Salticus scenicus_).
]

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_).

FIG. 125.—Mange Mite of the Pig (_Sarcoptes scabiei_, var. _suis_),
seen from the ventral side.
]

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.

FIG. 126.—Mange Mite of the Pig (_Sarcoptes scabiei_, var. _suis_),
seen from the dorsal surface. × 200.
]

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.