REARING TICKS. 87 
This class of animals was usually allowed to remain in the attachment 
cages for 5 or 6 hours, specimens not attached at the end of that time 
being returned to rearing tubes. 
REARING TICKS. 
In rearing ticks one of the first considerations is to eliminate, so 
far as possible, the danger to the experimenter of infection by disease- 
bearing species. This requires great care in manipulation, and com- 
plete isolation, by water and grease or some other substance, of all 
specimens likely to be infected. 
Although it is desirable that the usual host be used in determining 
the parasitic periods, so that variations from the normal condition 
may be eliminated, this was not always possible. In a few instances 
small wild mammals which were captured in nature have been uti- 
lized for the rearing of ticks and the study of their habits. Animals 
which have become infested in nature may often be successfully 
employed in the study of the habits of the ticks with which they are 
infested. Most of the species which we have studied attach to 
domestic animals, and as nearly all of these attach to a bovine, we 
have largely made use of this host in determining the parasitic periods 
and habits of the species. The method found most satisfactory is 
that suggested by Prof. C. P. Lounsbury, of attaching a bag over the 
scrotum of a bovine. In this way the various stages of ticks were 
applied, examinations made, and the ticks removed as they dropped, 
and comparatively few were lost. All of the ixodids, except certain 
species of Ixodes, thus applied by the writers, have attached in one 
or more stages. Some species, Dermacentor variabilis in particular, 
attach with considerable reluctance. By removing the bag and with 
it the unattached ticks at the end of a given period and then replacing 
the bag and making examinations twice daily and removing the 
engorged ticks from it, the exact periods of engorgement were deter- 
mined. In order to prevent the removal of the bag from the scrotum 
by the host a harness has been employed in some instances and in 
others leather or wire muzzles have been found satisfactory (Plate IJ). 
With the ticks which pass both molts upon the host, as do Marga- 
ropus annulatus, Dermacentor nitens, D, albipictus, and O. megnini, it 
is a comparatively easy matter to follow the life cycles, but with those 
which drop from the host to molt, as is the case with most of our 
North American species, it is much more of a task. With those 
species which drop for each molt one must succeed in getting the 
same individuals to attach to the host and catch them as they drop 
three or more different times. After dropping each time they must 
be isolated under favorable conditions and frequent examinations 
made to determine the periods of molting and ovipositing. In order 
to present satisfactory information upon these periods the periods 
