66 
Adaptation of Ticks 
Summary. 
A consideration of the facts presented in the foregoing pages 
appears to warrant certain conclusions which must, however, be regarded 
in part as provisional and subject to revision when our knowledge of 
the various species of ticks has become more extended. The views 
here expressed may prove of practical use in the study of the Ixodidae. 
The Argasidae represent the relatively primitive type of ticks 
because they are less constantly parasitic than are the Ixodidae. Their 
nymphs and adults are rapid feeders and chiefly infest the habitat of 
their hosts. In certain Argasidae (0. mouhata and 0. savignyi) the 
disadvantage of their possessing an “active ” larval stage has resulted 
in the development of an “ inactive ” larva, i.e. the young nymph being 
the first to suck blood. In 0. megnini we have a considerable adaptation 
brought about by the difficulty there must be in the tick entering the 
small aperture of the ear more than once. Owing to the Ai’gasidae 
infesting the habitats of their hosts, their resistance to prolonged 
starvation and their rapid feeding habits, they do not need to bring 
forth a large progeny, because there is less loss of life in the various 
stages, as compared to Ixodidae, prior to their attaining maturity. 
The Ixodidae are more highly specialized parasites than the pre¬ 
ceding. The majority are parasitic on hosts having no fixed habitat 
and consequently all stages, as a rule, occur upon the host. In the 
genus Ixodes we find an adaptation of certain species according to the 
habits of the hosts upon which they are parasitic. In the species which 
usually occur upon wandering hosts both sexes are found upon the 
host, whereas in other species which occur on hosts possessing more or 
less fixed habitats the males are rarely or never found upon the host. 
The males of species of Ixodes, both sexes of which occur upon the host, 
are characterized, as a rule, by the possession of hypostomes with 
prominent teeth, the reverse being the case in forms wherein the males 
do not occur upon the host. Where species occur upon a wandering 
host it is essential, for their propagation in nature, that both sexes 
should be carried about upon the host. 
It appears to follow that the copulation of ticks upon the host is an 
indication of a higher degree of specialization to a life of parasitism. 
When copulation does not take place on the host, we have merely the 
retention of a primitive character as found in Argasidae. From the 
