56 
Adaptation of Tichs 
armed with long pointed teeth running down to its base (Figs. 9, 10). 
The adults or nymphs of these species (Figs. 11, 12, 13) show a con¬ 
siderable reduction in the armature of their hypostome. In 0. savignyi 
and 0. mouhata, where the larvae are inactive and the nymphs and 
adults are both rapid feeders, the dentition of the hypostome is 
reduced (Figs. 14, 15, 16). In 0. megnini the larval hypostome 
(Fig. 17) is powerfully armed, and the same is the case with that 
of the nymph (Fig. 18), 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 
marked 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 {d'), japonensis, pei'- 
cavatus, cordifer (</), tasmuni and coxaefurcatus (cf). We nevertheless 
include two of these {percavatus and tasmani) in the subjoined lists 
because the presumption appeals 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 fi'om 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 evidence is not 
quite satisfactory. 
