338 



Appendix II 



[60] 



Microdidelphys sorex (o & L 1 .) 



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 (only found once) the sexes may occur together on the host for 

 the reasons stated above for tenuirostris ; loricatus appears to be an 

 exception. 



If the reader will run his eye down the column of + and signs in the 

 lists I (pp. 336-338) and II (pp. 339-340) 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 with most 

 of the other hosts ; in only two instances out of 23 has this species 

 been recovered from a wandering host. 



1 o and h signify that nymphal and larval stages only were found. 



