G. H. F. Nuttall 
65 
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. 
Figs. 19—20 represent the hypostomes of I. ricinus <? and $ . That of the s may be 
taken as the type of a hypostome with large basal teeth as observed also in the males 
of rasus, iigandanus, schillingsi, rubirundus, cavipalpus and pilosus, the basal teeth 
being less prominent in the last two species mentioned. In loliviensis <? the basal 
tooth, whilst prominent, is much less developed. 
Fig. 21 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.) 
Fig. 22 represents the hypostome of I. holocyclus <? . It is poorly but relatively better 
armed than that of canisuga which follows. 
Fig. 23 represents the hypostome of I. canisuga <J , poorly armed, and much emarginated 
distally. That of hexagonus is similar but not emarginated. 
Fig. 24 represents the hypostome of I. putus S , 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. 25—26 represent the hypostomes of I. vespertilionis S and ? ; that of the g practi¬ 
cally unarmed ; that of the $ illustrating the dimorphism existing between the sexes. 
The figures are chosen from the series illustrating Ticks, Part II (in press), 
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 th® host. 
Parasitology iv 
o 
