18 LIFE HISTORY OF NORTH AMERICAN TICKS. 
instances living and dead ticks have been found clinging to the skins 
of animals which have been nailed on a wall for several days. 
The collection of ticks from herbage, on which they are awaiting a 
host, may best be done by dragging a white cloth, preferably of wool, 
over bushes, grass, etc. An ordinary insect beating net may also be 
employed. Fruitful results have been found to attend the examina- 
tion of the dens of animals, nests and regular roosting places of birds, 
and the ground in the vicinity of resting and watering places of 
mammals. Pill boxes have been found to be satisfactory receptacles 
for the ticks when collected. 
In preserving we have usually used 80 per cent alcohol or a mixture 
consisting of 60 parts alcohol, 1 part formalin, and 39 parts water. 
Adult specimens, particularly males with bright color markings, 
should be mounted on pins, as well as preserved in alcohol. For 
microscopical study specimens should be mounted in Canada balsam 
on slides. The contents of the body should first be teased out in hot 
water, through a slit made at the posterior end of the body. Speci- 
mens can then be readily cleared by boiling in a 10 per cent solution 
of caustic potash (KOH), care being taken that the clearing be not 
carried too far. The method employed by Dr. C. W. Stiles consists 
in soaking the specimens in from 2 to 5 per cent caustic-potash 
solution for periods varying from 12 to 96 hours, after which all of 
the soft body content is removed, and after passing the specimens 
through water, the alcohols, and xylol or other clearing agents, the 
specimens are mounted in balsam. 
ECONOMIC IMPORTANCE. 
Ticks are of economic importance (1) as agents in the transmission 
of infectious diseases, and (2) as external parasites, both of man and 
the lower animals. At least two distinct diseases of man and eight or 
more of domestic animals are known to be thus transmitted, at 
least 17 species of ticks bemg involved as carriers. Of these dis- 
eases one of man and one of cattle occur, and one of fowls is sus- 
pected to occur, in the United States, while several others would 
undoubtedly obtain a foothold were they once introduced. 
It has been estimated by Dr. Mohler (1905) that the cattle tick 
alone is the source of approximately $40,000,000 annual loss in the 
United States. Mayer (1906) has estimated the annual loss as nearly 
$100,000,000. : 
These parasites are of considerable importance as external parasites, 
particularly in the Southern States, owing not only to their irritation 
and great drain upon stock through removal of blood, but also to their 
indirect effect as well. In one of Theiler’s experiments (1909a) a 
horse that was infested with Margaropus decoloratus died as a result 
of infestation from acute anemia due to the withdrawal of blood. 
