ANIMAL PABASITES AND PARASITIC DISEASES 



327 



eggs to the hair. After a varying period the young and complete 

 insect raises the operculum from the large end of the egg, opposite 

 to the point of attachment, and crawls out. In a short time 

 it develops into an adult louse and is capable of reproduction. 

 Lice multiply very rapidly under warm, moist conditions. In- 

 fested animals are said to be lousy. 



Each species of animals is attacked by two or more kinds or 

 species of lice. As a rule, the lice of cattle will not pass to horses, 

 hogs, or poultry; the reverse is also 

 true. 



The horse is commonly infested 

 with one of two species of lice, but 

 rarely with both at the same time. 

 The Hematopinus macrocephalus is 

 characterized by a long, narrow 

 head and large, oval abdomen (Fig. 

 81). It measures slightly more than 

 3^6 mc h long, and obtains its living 

 by biting and sucking the blood from 

 its host. The Tricodectes pilosus 

 has a head that is rounded in front 

 and is broader than it is long. This 

 louse lives principally on the epider- 

 mal scales of the horse. It is about 

 hah the size of the former. 



The lice found most frequently on 

 cattle belong either to the blood- 

 sucking species, commonly known as 

 "blue lice," or the biting species, 

 commonly known as the "little red 

 louse." 



There are three methods of applying treatment to eradicate 

 lice, viz., hand applications, spraying, and dipping. The method 

 adopted will depend on the season of the year, remedy selected, 

 and number of animals to be treated. 



Hand applications are applied in the form of dusting powders, 

 and liquids. The insecticidal value of dusting powders for lice 

 is questionable, although many different kinds are on the market. 

 Ointments are useful if properly compounded. Probably 

 "blue ointment" is most effective, but it contains bichlorid of 



Fig. 81. — The common horse- 

 louse (Hematopinus macrocepha- 

 lus) greatly enlarged. 



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