Screw-worm fly (Chrysomyia macellaria). — Whitish maggots, three-fourths inch in length when full grown, infesting sores and wounds of animals in the Southern States. The eggs are laid on the wounds in masses of 100 or more by a bright, metallic green fly a little larger than the house-fly. The maggots enter the wound, feed on the putrid matter within, and as they increase in size burrow into the flesh, freCATTLE AND HORSE PARASITES quently excavating a large cavity. The purulent discharge from such sores attracts other flies to lay their eggs, more maggots enter the wound, and unless aid is rendered the animal dies. A slight scratch or merely a mass of blood from a crushed tick may serve as a starting-point for the trouble. The flies also breed in decaying carcasses.

Treatment. — Prevent the deposition of eggs by washing all wounds as soon as noticed with a disinfectant, and then apply a dressing of pine tar or tar and grease. When wounds are found infested, dislodge the maggots by injections of carbolic acid diluted with 30 parts of water, or one of the coal-tar sheep dips may be used. After the maggots have been removed and the sore thoroughly disinfected, dress the wound with a coating of pine tar. Deep sores should be packed with sterilized absorbent cotton.

By careful attention to the destruction of garbage, carcasses, and other filth in which the maggots breed in enormous numbers, much loss may be avoided. Carcasses left to decay exposed to the air about pastures are constant sources of danger.

Horse. Horse bot-fly (Gastrophilus equi). — The light yellow eggs are glued to the hairs on the shoulders, forelegs, and under side of the body by a brownish fly about three-fourths inch in length. By licking these parts the egg-cap is removed and young maggots taken into the mouth. On reaching the stomach they attach themselves to the walls and remain there until the following spring. When abundant they may nearly cover the whole inner surface of the stomach, interfere with the secretion of the digestive juices, and by collecting near the pyloric opening prevent the natural passage of the food from the stomach. When mature they loosen their hold and are voided with the excrement in late spring. These full-grown bots are about three-fourths inch in length ; they burrow into the ground where the pupal stage is passed. The flies emerge thirty or forty days later.

Treatment. — Remove the eggs within a week after they have been deposited by clipping the hair, or destroy them by washing with a solution of carbolic acid in 30 parts of warm water. When only a few bots are present in the stomach, they do not seem to cause the animal inconvenience ; when very abundant, they may cause fretting and colic, and the horse may loose flesh. In such cases consult a veterinarian.

Sheep. Sheep bot-fly or head-maggot (CEstris ovis). - The dark brownish parent flies, somewhat larger than the house-fly, emerge during June and July, and deposit living maggots in the nostrils of sheep. The animals have an instinctive fear of the flies, and are thrown into a panic by their attack. The maggots work their way up the nostril, and find lodgment in the frontal sinuses, where they feed on the mucus. Their presence causes great irritation and the discharge of purulent matter. Sometimes the maggots penetrate into the brain cavity, and death may result.

Treatment. - It is almost impossible to dislodge the maggots by the injection of any substance, and such treatment is not advised. Never try to extract them with a wire. To prevent the flies from depositing their young, smear the sheep's nose with tar and grease. This is most easily done by placing in the pasture logs in which holes have been bored. Salt is placed in the holes, and the edges smeared with grease and tar. In trying to get the salt the sheep will keep their noses covered with the tar.

Sheep scab (Psoroptes communis). - The cause of this disease is a minute mite which lives on the skin under a scab or crust and causes the wool to fall out in large irregular patches. The irritation causes intense itching, the sheep become restless, lose in weight and vitality, and in severe cases die. The disease is contagious and may be transmitted either directly from animal to animal or by means of infested quarters, cars or pasture fields.

Treatment. - Dip the infested or suspected animals in some reliable sheep dip at the temperature of about 100° Fahrenheit ; hold the sheep in the liquid two or three minutes, and immerse the head once or twice just before the sheep is released. Soften thick scabs before dipping by wetting with some of the dip and by rubbing with a smooth stick, taking care not to draw blood. Repeat the dipping in ten days or two weeks to kill any mites which may have hatched from eggs since the last treatment. After dipping do not return the sheep to the same field in less than thirty days, to avoid reinfestation. When it is necessary to return the sheep to the same barn or pen, these quarters should be thoroughly cleaned and disinfected with cresol or some other coal-tar dip, used at the rate of one part to 50 parts of water. The addition of whitewash to the disinfectant will serve as a marker and show when the work has been thoroughly done. Avoid introducing the disease by having all sheep brought from infested regions dipped before delivery.

Sheep tick (Melophagus ovinus). - Reddish or gray brown, flattened, wingless flies that infest sheep of all ages, but are most injurious to lambs. They remain on the sheep throughout their whole life cycle. The young are nourished within the mother until full grown, and are ready to pupate when born.

Treatment. - The nicotine-and-sulfur dip has given the best results in the control of this pest ; many of the commercial cresol and coal-tar creosote dips are also effective. The lime-and-sulfur dip will not kill the ticks. When only a few are to be treated, kerosene emulsion may be used as a spray and rubbed into the wool.

Swine. Hog louse {Haematoyinus suis). - Lousy hogs are likely to be in a stunted, unthrifty condition, and when badly infested the skin becomes covered with scales and sores.

Treatment. - Clean and whitewash the pens and sleeping quarters, adding 1 pint of crude carbolic acid to each 4 gallons of the whitewash. Spray or dip infested animals with 10 per cent kerosene emulsion, or use the tobacco-and-sulfur sheep dip. Repeat the application in two weeks to kill any lice that may have escaped. A wallowing trough containing five to eight inches of water on which is floated a thin layer of crude oil is frequently used with success.