x 



[From the Kcport S^j^X^ftW^ of Agriculture for 1870.] 



The External Parasites of Domestic Animals, 



THEIR EFFECTS AND REMEDIES.* 



BY A. E. YERBILL. 



The external parasites of our domestic animals nearly all 

 belong to the great class of animals which we call Insects, but 

 the internal parasites are, with few exceptions, representatives 

 of the class of Worms. The division of the subjects of these 

 lectures is, therefore, both convenient and natural. 



The class of Insects includes a far greater number of spe- 

 cies than any other class of animals, the number actually 

 amounting to several hundred thousands, each country having 

 a vast number peculiar to itself. They are also exceedingly 

 diverse in habits, as well as in form and structure. 



In order to show the affinities of the insect-parasites and 

 their position among other insects, it will be necessary to give 

 a brief sketch of the whole class, with a few remarks on the 

 more important peculiarities of their anatomy. 



All insects, like the other articulated animals (worms and 

 Crustacea), have a body composed of a series of segments or 

 rings, placed one behind the other, and together forming a 

 sort of irregular tube, which incloses in one cavity all the in- 



* In the preparation of the reports of these lectures on the parasites of domes- 

 tic animals, we are greatly indebted to Dr. A. S. Packard for the use of many 

 cuts of insects from his excellent "Guide to the Study of Insects" and the 

 "American Naturalist," published at Salem, Mass.; and to Donald G. Mitchell, 

 Esq., editor of the "Hearth and Home," published by Pettingill, Bates & Co., New 

 York, for the use of several excellent cuts of parasitic worms, prepared to illus- 

 trate a series of articles on parasites of man and domestic animals by the writer. 

 Without this assistance the lectures could have been illustrated only imperfectly. 

 In addition to these we have added, so far as the available funds would admit, fig- 

 ures of the more important parasitic insects and worms, copied from Cuvier, Gue- 

 rin, Clark, Leuckart, Cobbold, and others. A. E. Verrill. 



