524 HORSE, SWINE AND POULTRY DISEASES 



an inch in length and one-fifth as broad. It comprises three parts ; 

 head, thorax, and abdomen, the first two being joined in a single 

 organ. The mouth parts are horse shoe shaped. Their length and 

 the cephalo-thorax is about equal to the length of. the abdomen. 

 The mouth parts comprise, first a pair of mandibles; second a pair 

 of jaws; third a narrow tongue. On the sides of the thorax are 

 four pairs of short, mobile legs formed of three parts, the last part 

 being fitted with two claws. The abdomen is long, conical and 

 striated transversely. It shows at the anterior part of its ventral 

 face a longitudinal slit, the anus, which is much larger in the 

 female than in the male, and may serve for copulation and ovula- 

 tion. The abdomen of the male is less developed than that of the 

 female, and possesses a genital armature situated immediately in 

 front of the anus. 



The young parasites are small and narrow and have but three 

 pairs of legs. The eggs average twenty five-hundredths of an inch 

 long and are ovoid in shape. The larva undergoes three metamor- 

 phosis before reaching the adult state. It no doubt passes through 

 the different stages of development in the follicles of the skin, but 

 may migrate over the surface of the skin when it reaches the adult 

 stage and before laying eggs. 



Symptoms. The finer parts of the skin are affected; the 

 snout, neck, chest, abdomen, flank and inner part of the thighs. 

 The inflammation begins in the region of the hair follicles and 

 sebaceous glands. Pimples and pustules appear, varying in size 

 from that of a grain of sand to that of a hazelnut. As the disease 

 progresses large purulent islands varying in size and containing 

 many acari are formed. Ulceration may follow. In the older dis- 

 eased areas and when the disease lasts for a long time, the skin 

 becomes sclerotic (hard) and many times its normal thickness. 

 Inside of the pimples the mites can be found in all stages of devel- 

 opment. In the small abscesses there may be from fifty to one 

 hundred, in the larger ones a thousand. Follicular mange is said 

 to be more contagious in the hog than it is in other animals, and 

 is considered a serious disease. 



The scab mite is one of the largest of the specie and when 

 found can be seen with the naked eye. They work deep in the 

 skin, and it is difficult to find them. The female is about one- 

 fiftieth of an inch long and almost as broad. The male is not aa 

 large. The mite has eight very short, thick, conical shaped legs, 

 the two posterior ones being quite or almost concealed beneath the 

 abdominal surface. On the dorsal surface are a number of par- 

 allel ridges interrupted by conical projections. Toward the pos- 

 terior part of the body are a few hairs. 



Symptoms. It begins with a violent itching about the head, 

 especially at the base of the ears, about the eyes, and gradually ex- 

 tends to the neck, withers, inner surfaces of the thighs and the 

 whole body. The invaded areas of the skin are first covered with 

 little red pimples. Abrasions from the hog rubbing itself soon 

 occur. The secretions and scales from the skin gradually accumu- 



