Biology 295 



hexagonus and canisuga, the evidence afforded being sufficient to make 

 it possible to identify the different stages of these species. Lounsbury, 

 at the Cape, has raised pilosus experimentally; and Hadwen, in British 

 Columbia, has made partial raising experiments on angmtus. Of the 

 remaining species whose various stages are known {tenuirostris, ves- 

 pertilionis and loricatus), the close resemblance between the various 

 stages encountered upon the same host has been accepted as sufficient 

 evidence for their belonging to the same species. This method of 

 identification has been applied to nearly all the other species we 

 recognize in which the life-histories are less completely known. Strictly 

 speaking, the identification of males and females as belonging to one 

 species should depend upon their being found in copula; but failing 

 this, we are obliged to rely upon the evidence afforded by their mor- 

 phology and their both occurring together upon a host. 



In the list of recognised species, given in the table at the end of this 

 fasciculus, the table serving likewise as an index, the various stages of 

 each species known to science are indicated by the signs </", $, o, L, 

 which stand for male, female, nymph and larva respectively. From this 

 list it will be seen, if we exclude varieties of some of the species, that 

 the 



</, $, o and L are known in 8 species. 



J, % and o „ „ „ 4 



</" and % „ „ „ 6 



o is >> » " »> 



+ >. » » «" » 



$ and O, are „ „ 4 „ 



$, o and L, „ „ „ 6 



It follows that these species are known by 21 Js, 48 £s, 22 os and 14 

 larval forms. 



Outline of the life-history in Ixodes. 



Before proceeding further, it appears expedient to briefly outline the 

 life-history of an Ixodes as typified by Ixodes ricinus. I shall leave 

 out of consideration the changes which take place in the internal anatomy 

 of the ticks whilst attached to the host and subsequently, for these 

 matters will be considered in a special section of this work. I propose 

 here to merely outline the main facts in the life-history. 



