334 Appendix II [56] 



armed with long pointed teeth running down to its base (Figs. 290, 291). 

 The adults or nymphs of these species (Figs. 292, 293, 294) show a con- 

 siderable reduction in the armature of their hypostome. In 0. savignyi 

 and 0, moubata, where the larvae are inactive and the nymphs and 

 adults are both rapid feeders, the dentition of the hypostome is 

 reduced (Figs. 295, 296, 297). In 0. megnini the larval hypostome 

 (Fig. 298) is powerfully armed, and the same is the case with that 

 of the nymph (Fig. 299), which we have seen remains attached for 

 a long time to the host. The hypostome of the adults, which do 

 not suck blood, is unarmed, and the capitulum, as a whole, is quite 

 exceptionally small. The figures are reproduced from Ticks, Part I, 

 without regard to the relative magnifications employed. 



Ixodes. 



When we come to consider the biology of Ixodes, which are clearly 

 maiked off from other Ixodidae structurally, there .are. two points 

 which are very striking in respect to the adult stages: (1) the con- 

 siderable number of species in which the females only are known, and 

 (2) the fact that the males of some species are frequently found in 

 copula on their hosts (in some species the sexes remain in copula even 

 when they are dropped into spirit). In no other genus of Ixodoidea 

 is this the case. On the other hand, in those species in which both 

 sexes are known, some are found in copula upon the host, whilst others 

 are not. I have sought a reason for these peculiarities in Ixodes, and 

 believe I have found an explanation of these differences. I shall begin 

 by discussing the host relationships in Ixodes. 



Of the 51 species listed we have no data regarding the hosts of nine, 

 namely, nigricans, fossulatus, acutitarsus, gigas (</"), japonensis, per- 

 cavatus, cordifer (<?), tasmani and coxaefurcatus (,/). We nevertheless 

 include two of these (percavatus and tasmani) in the subjoined lists 

 because the presumption appears justified that they came from birds : 

 percavatus came from isolated islands in the Pacific inhabited by birds, 

 and we possess a variety of this species, taken from a puffin ; tasmani 

 was collected on the Island of St Pierre, and by the celebrated ornitho- 

 logist, Jules Verreaux, in Tasmania. We therefore are able to list 

 44 species in relation to their hosts, there being, but two of these 

 (percavatus and tasmani) with regard to which the eyidence is not 

 quite satisfactory. 



