[65] 



Adaptation of Ticks 



343 



Figures illustrating the hypostomes of Ixodes. 



The accompanying figures show the marked sexual dimorphism which is observable in 

 some species of Ixodes, and also types of male hypostomes which show considerable 

 modifications of structure. 



300 301 



Pigs. 300, 301 represent the hypostomes of I. ricinus i and ? . That of the <? may be 

 taken as the type of a hypostome with large basal teeth as observed also in the males 

 of rasus, ugandanus, schillingsi, rubicundus, cavipalpus and pilosus, the basal teeth 

 being less prominent in the last two species mentioned. In boliviensis <f the basal 

 tooth, whilst prominent, is much less developed. 



Pig. 302 represents the hypostome of I. minor s , with well-developed outer files of teeth. 

 (The hypostome of tenuirostris and loricatus approximate to the type of structure 

 found in the females.) 



It is poorly but relatively better 



Fig. 303 represents the hypostome of I. holocyclus <r . 

 armed than that of canisuga which follows. 



Fig. 304 represents the hypostome of I. canisuga i , poorly armed, and much emarginated 

 distally. That of hexagonus is similar but not emarginated. 



Fig. 305 represents the hypostome of I. putus l , practically unarmed, emarginated, and 

 so reduced in length as to be useless for attaching the tick to a host. This structure 

 alone suggests that the male of this species is probably incapable of sucking blood. 



Figs. 306, 307 represent the hypostomes of I. vespertilionis s and ? ; that of the s practi- 

 cally unarmed ; that of the ? illustrating the dimorphism existing between the sexes. 

 The figures are chosen from the series illustrating this work, without regard 

 to the magnifications employed. 



N.B. — It is a striking characteristic of hexagonus, canisuga, putus and vespertilionis males 

 that the capitulum is much smaller compared to the size of the body than in any other 

 male Ixodes that are known. The size of the capitulum apparently bears a direct 

 relation to the dentition of the hypostome and to the habits of the male with regard 

 to copulation and parasitism on the host. 



