_The common sucking lice_ occurring on animals are the large-headed horse louse, _H. macrocephalus_; the long-nosed ox louse, _H. tenuirostris_; the large-bellied ox louse, _H. curysternus_; the _H. stenopses_ of sheep; _H. suis_ of swine; and the _H. piliferus_ of the dog. The _common biting lice_ (Fig. 63) that are found on domestic animals are the _T. pilosus_ and _T. pubescens_ of solipeds, _T. scalaris_ of the ox, _T. spoerocephalus_ of sheep and goats, _T. latus_ and _T. subrostratus_ of the dog and cat. _Menopon palidum, Lipiurus variabilis_ and _Gonoides dissimilis_ are the common lice found on poultry. [Illustration: FIG. 63.--Biting louse.] SYMPTOMS OF LICE.--The symptoms of lousiness depend on the variety of lice present, the degree to which the animal is infested with them, its physical condition and the care that it receives. Lice multiply more rapidly and cause greater loss during the winter months than they do in the summer, when the animals are not housed and the opportunity for infection from the surroundings is not so great. The sucking louse (Fig. 64) is the most injurious and irritating. The irritation and loss of blood that the animal may suffer when badly infested by this parasite may result in marked unthriftiness. Young and old animals that are not well cared for suffer most. The biting louse may bite through the superficial layer of the skin, and cause the animal to bite and rub the part. This irritation to the skin prevents the animal from becoming rested, and after a time seriously interferes with its thriftiness. _Horses and mules_ show a staring, dirty, rough coat. The mane and tail may become broken and matted. The animal rubs against the stall, fences and trees, and bites the skin in its efforts to relieve the irritation. On examining the coat, nits are found adhering to the hair (Fig. 65). We should examine the parts of the skin covered by the long hair for the sucking lice; and the withers, abdomen and limbs for the biting lice. [Illustration: FIG. 64.--Sucking louse (much enlarged).] [Illustration: FIG. 65.--Nits attached to hair (much enlarged).] _The symptoms of lousiness in cattle_ are about the same as occur in horses. Licking and rubbing the skin are prominent symptoms in cattle, and the coat becomes dirty and rough. The licked part is matted and curled. The lice may be discovered by parting the hair along the back and rump. _The biting louse of sheep_ causes the fleece to become matted and tufts of wool are pulled out. This is brought about by the sheep rubbing and nibbling the fleece, and the lice cutting through the wool. The loss due to the damage to the fleece is usually greater than that resulting from unthriftiness.