HOST RELATIONSHIP. 25 
while attached appears to be a special adaptation. One native 
species (Ornithodoros megnini Dugés) and several exotic species 
(Rhipicephalus evertsi, R. bursa, Hyalomma zxgyptium) pass the first 
molt upon the host, but drop for the second. A few species, includ- 
ing Margaropus annulatus and its several varieties, Dermacentor 
albipictus and Dermacentor nitens, pass both molts upon the host. 
As yet none is known to drop for the first molt and to pass the sec- 
ond upon the host. 
HABITS. 
HOST RELATIONSHIP. 
Several species of ticks seem to be naturally restricted to a single 
genus or family of hosts, such as Hemaphysalis leporis-palustris and 
Dermacentor parumapertus marginatus to the Leporide. Others, 
although attaching to some hosts more or less frequently (second- 
ary hosts), have particular hosts (primary hosts) to which they 
more commonly attach. From this habit have arisen many of our 
common tick names, such as the cattle tick, dog tick, rabbit tick, ete. 
Ticks occasionally attach themselves to animals which may be 
termed accidental or temporary hosts. This fact is aptly illustrated 
by the cattle tick, large numbers of which, in the first experiments, 
were repeatedly placed upon dogs by the writers, but without becom- 
ing attached. Finally, however, during the summer of 1908 several 
ticks attached themselves to the laboratory dogs and later, on 
these host animals, developed to replete females. There seems to 
be a rather close analogy between ticks and fleas with regard to 
hosts. In his revision of the Siphonaptera (1904, p. 368), Baker 
mentions rabbit fleas as remaining on a human being for some little 
time, biting frequently while there, but not frequenting the human 
host nor his clothing or bed. To illustrate how fleas would find 
these temporary hosts, he mentions the possibility of a rabbit run- 
ning into a badger hole, or a mouse into a mole burrow; that the 
eating of a mouse by an owl or the devouring of a rat by a cat would 
afford favorable conditions for this temporary transference of para- 
sites. Similar instances account for many of our accidental hosts 
of ticks. It thus appears that larvee of Amblyomma tuberculatum 
become attached to hawks and owls at the time their small mammal - 
hosts are being devoured. 
Experiments conducted by the writers have shown that when 
confined in a bag in close proximity to the scrotum of a bovine, 
nearly all of the ixodids will attach. As a result of these accidental 
or temporary attachments for some species we have large host lists, 
including hosts upon which the ticks could only occasionally or never 
reach maturity. Prof. Lounsbury has found a peculiar habit in 
Hyalomma xgyptium impressum. As a larva, it will not feed on the 
