34 LIFE HISTORY OF NORTH AMERICAN TICKS. 
that ticks may go while in search of a host. Although the dis- 
tance traveled by seed ticks, as the writers have observed them 
on grass in cages, is comparatively slight, the adults may be found 
to crawl considerable distances. This appears to be the case with 
the brown dog tick (Rhipicephalus sanguineus), which is very agile 
and constantly moving about when not attached. We have found 
the males of this species to travel from one dog to another when 
the hosts were lying asleep in the laboratory. The adults of 
Dermacentor parumapertus marginatus can crawl considerable dis- 
tances in a comparatively short time, their movements being very 
rapid. 
The usual method by which ticks are disseminated is by the natural 
movement of the hosts or by the shipment or driving of the host from 
one locality to another. The following are good illustrations of how 
far ticks may be carried upon their usual hosts: The cattle tick has 
been found on ponies in Michigan, as well as upon cattle at various 
times in the extreme northern parts of the United States prior to the 
establishment of a quarantine against this tick. Amblyomma dis- 
simile has been brought into Texas on iguanas from the Isthmus of 
Tehuantepec, and according to Barber (1894, 1895) Amblyomma 
variegatum (Hyalomma venustum) has been introduced into the Leeward 
Islands on cattle shipped from Senegal,in Africa. That there is abun- 
dant opportunity for ticks to be carried long distances in this way may 
be seen from the fact that Ornithodoros megnini has been found to 
remain upon a host as long as 209 days before dropping. Birds, 
especially migratory species, may carry ticks long distances. In 
one instance Mr. W. V. King, of the Bureau of Entomology, found a 
number of engorged larvee of a species of Ornithodoros, which appears 
to be confined normally to the Southern States, on the head of a 
bird in northern Wyoming. Among other means of natural dissemi- 
nation which may be of importance are streams and floods (as men- 
tioned by Hunter and Hooker, 1907, p. 24), high winds, and the 
movement of animals which are not hosts but to any of which ticks 
may cling for a greater or less time. Ticks may be artificially dis- 
seminated by means of the movement of various farm commodities, 
especially hay; by crates in which poultry or animals have beencon- 
fined; by the shipment of hides of animals, and in the clothing of 
man. 
SEASONAL HISTORY. 
The seasonal prevalence of ticks varies considerably from year 
to year with the temperature conditions. In some species the winter 
is passed in the egg, unengorged larval, nymphal, or adult stages. 
Females which drop engorged after the approach of cold weather 
stand a very poor chance of surviving. Ricketts (1909a, p. 102) 
reports having obtained ticks, largely engorged nymphs, at Hamil- 
