60 
Adaptation of Ticks 
Species 
Host’s 
habits 
Number of 
times found 
Host thereon 
Geographical 
distribution 
of tick 
I. ruhicundus var. Um- 
-1-. 
Sheep ... ... ... 1 
C. Africa (Congo). 
hatus ( ? only known) 
+ 
Goats 
I. holocyclus 
-f 
Bos taurus 
Australia, India. 
-t 
Macropus sp. 
Canis familiaris 
0 
Sciurus variabilis 
0 
Phascogale penicillata (Mar¬ 
supial tree shrew) 
I. loricatus 
+ 
Ateles melanochoerus 
S. America. 
0 
Didelphys aurita 
0 
,, opossum 
0 
,, sp. 
0 
Microdidelphys sorex (o & Lh) 
occurs as a parasite on small mammals which burrow ; these burrows 
are, however, near the surface of the ground and liable to be destroyed 
or flooded, consequently, for the- maintenance of the species, it is es¬ 
sential that both sexes should be carried about upon the host as in 
the case of ticks occurring on hosts with wandering habits. The other 
species follow the same general lines as 1 (a) with regard to their host 
relationships; the majority of the hosts have wandering habits. In 
minor (orrly found once) the sexes may occur together on the host for 
the reasons stated above for tenuirostris ; loy'icatus appears to be an 
exception. 
If the reader will run his eye down the column of -f and 0 signs in the 
lists I (pp. 58—59) and II (pp. 61—62) of the hosts of the different 
species of Ixodes, he cannot but be struck by the differences. The 
hosts enumerated in II, under “ Species of which the females only have 
been found upon the host, the males being known,” are nearly all 
animals which burrow or nest. Thus, we record the finding of hexagonus 
no less than 40 times on such hosts, once each on three wandering hosts 
(if we include man), and three times on the dog. The list of hosts of 
hexagonus var. cookei (taken from Banks) falls in with that of hexagonus. 
In the case of canisuga, the dog is the most prominent host, simply 
because nearly all of our specimens from the dog came from the north 
of England where the shepherd dogs are largely confined in kennels. 
The dog in these regions is a host with a fixed habitat, as wfith most 
of the other hosts ; in only two instances out of 23 has this species 
been recovered from a wandering host. 
1 o and L signify that nymphal and larval stages only were found. 
