382 



BUKEAU OF ANIMAL INDUSTRY. 



have been obliged to depend very largely upon Neumann's papers for 

 the analytical keys to the species of the different genera. Some of the 

 characters selected by him appear to us, however, rather difficult to use. 

 We have accepted Neumann's synonymy^ in almost every instance 

 except in Boophtlus^ since he has had at his disposal not only a large 

 number of specimens, but many types as well. Neumann's classifica- 

 tion is here followed, except for some slight changes. It seems to us, 

 for instance, that the differences between the two chief groups of ticks 

 are sufficiently great to admit of two families, rather than two subfam- 

 ilies. We also recognize the genus Boophilus^ and in this we distin- 

 guish, with Fuller, at least three species, namely, JB. annulatus^ B. 

 audralis^ and B. decoloratus. 



In selecting the technical names the International Code of Nomen- 

 clature has been followed. It must, however, be remarked that a 

 comparison of original type specimens may eventually result in slight 

 changes in the nomenclature adopted. Most of our technical names 

 agree with those adopted by Neumann, but we have considered it 

 necessar}^ to use Ixodes rlcinits instead of /. reduvms^ and to differ from 

 Neumann in regard to Linnaeus's Acarus americanus. (See p. 488.) 



In connection with the synonymy brief bibliographic citations have 

 been given, but no effort has been made to publish a complete bibliog- 

 raphy of the species discussed. The Harvard short method of citation 

 has been followed; full references may be obtained by consulting the 

 bibliography (pp. 478-488). 



THE POSITION OF THE TICKS IN SYSTEMATIC ZOOLOGY. 



Ticks are placed by zoologists in the Arthropoda, a very extensive 

 group, or phylum, which includes all animals possessing an external 

 chitinous skeleton, a ventral nervous system, dorsal digestive system, 

 together with jointed extremities. The group Arthropoda is divided 

 into a number of classes, the more important of which are — 



Hexapoda, or Insecta (insects), provided with three pairs of legs. 



Myriapoda (thousand legs), provided with numerous pairs of legs. 



Arachnoidea (spiders, ticks, mites, etc.), provided with four pairs 

 of legs. 



Crustacea (crabs, lobsters, etc., in most cases aquatic arthropods), 

 usually with a pair of extremities to each segment. 



Ticks belong to the class Arachnoidea, order Acarina, and are thus 



^ Many of the descriptions of ticks given by early authors are so incomplete that a 

 positive synonymy of all of the forms is out of the question. In many cases it is 

 impossible clearly to recognize the species with which an author is dealing, even 

 when he uses for it the name of a very commonly known form. On this account it 

 is frequently necessar}^ to accept in synonymy a bibliographic reference to a given 

 name simply because it is impossible to prove definitely that the reference under con-- 

 sideration does not deal with some other species than the one indicated by its name. 



