DISEASES OF THE SKIX. 343 



ing places are the tributaries to large rivers or streams; they select 

 places where the water runs slowly. The eggs are deposited \>y the 

 females just above the water's edge, upon any object projecting above 

 the water; they are mostly deposited in the forenoon, hatched out in a 

 few hours and the larvae fall into the stream. These larva? congregate 

 in swift water, where they live for nearly a year. Then they spin a 

 tough brown cocoon, with the upper end open, within which they become 

 transformed into pupa?, and in about ten days emerge as adult gnats. 



Treatment. When an animal has been weakened by an attack of 

 these gnats, give from 1 to 2 drams of carbonate of ammonia in 4 

 ounces of whisky every four hours. Keep the animal in a cool, dark 

 place. Occasional immersion in cold water has been beneficial. 



Prevention. Smoke from fires built of wet wood, burning leather, tar, 

 rags, etc., has proved the most practical for the purpose of keeping them 

 at a distance. As soon as the gnats appear build a fire, make as much 

 smoke as you can, and drive the cattle close up to it, where they will 

 remain as long as the pest is about. Whenever it can be done, stabling 

 the cattle during the day and turning them out from late in the even- 

 ing until early morning will be a reasonably safe measure to adopt. 

 Cotton-seed, oil mixed with tar, fish oil, kerosene, or carbolic acid, 

 applied to the cattle twice a day will protect them to a very great 

 extent. 



H^EMATOBIA 3EBBATA HORN-FLY. 



This is a small black fly, which first appeared in sufficient numbers 

 to attract attention in this country in the year 1887. In that year they 

 appeared in the counties adjoining Philadelphia, Pa. In the following 

 year they extended into Maryland, and a year later reached the Dis- 

 trict of Columbia and Virginia. They attack cattle in the fields by 

 piercing their skin and sucking the blood. When they are present in 

 large numbers they collect upon the roots of the horns, along the top 

 of the neck, or under the belly, thus proving a veritable pest among cat- 

 tle in the infested regions. From the fact that they congregate upon 

 the bases of the horns when they are at rest they have received the 

 popular name of " horn-fly ." They appear with the warm weather of 

 spring the early part of May and disappear after the first severe 

 frost in the fall. The flics are observed in the greatest numbers during 

 July. The characteristic habit of clustering about the base of the horn 

 seems to exist only when the flics are quite abundant. When they 

 average only a hundred or so to a single animal comparatively few will 

 be found on the horns. Moreover, as a general thing, the horn-cluster- 

 ing habit seems to be more predominant earlier in the season than later, 

 although the flies may seem to be nearly as numerous. The clustering 

 upon the horns, although it has excited considerable alarm, is not pro- 

 ductive of the slightest harm to the animal. The flies assume two char- 

 acteristic positions, one while feeding and the other while resting, h 

 is the resting position in which they are always found when upon the 



