182 LIFE HISTORY OF NORTH AMERICAN TICKS. 
different hosts was as follows: Cattle, 30; horse, 22; man, 16; deer, 
4; mule, 4; dog, 3; ass, 1; rabbit, 1; sheep, 1. While cattle, horses, 
and man are the hosts upon which most of our collections have been 
made, deer act as hosts for large numbers of adults. In some cases 
they are said to be infested with thousands of specimens. 
GEOGRAPHICAL DISTRIBUTION. 
(Fig. 15.) 
The type locality for this species is Occidental, Cal. Although this 
species has been reported from Texas, New Mexico, and Arizona, as well 
as California, it is very doubtful if the records from Texas, New Mexico, 
and Arizona are correct. Our records indicate that the species is 
confined to the Coast Range and Sierra Nevada Mountains in Cal- 
ifornia and Oregon and the small mountain ranges in southwestern 
California. The species occurs in great abundance in the extreme 
southern part of California, and it is therefore almost certain to 
occur southward in Lower California and western Sonora. 
LIFE HISTORY. 
No previous work seems to have been done on the life history of 
this species. Investigators of Rocky Mountain spotted fever have 
published a number of notes regarding the life history of Derma- 
centor venustus under the name Dermacentor occidentalis. 
The egg (Table LX XXIT).—In the laboratory in June, at a mean 
temperature of 87.19° F., deposition began in one case in 4 days. In 
April, with a mean temperature of 66.18° F., one tick had a preovipo- 
sition period of 14 days. The longest preoviposition period actually 
noted was 17 days. This record was on a female which was collected 
and mailed to the laboratory, hence the temperature and moisture con- 
ditions were notnormal. The average preoviposition period of 4 females 
dropped in April and May was 7? days. The average preoviposition 
of 17 lots of females collected during the period from March to June, 
inclusive, was 10.4 days. During April and May, 4 ticks showed a 
deposition period of from 27 to 39 days, with an average of 31} days. 
The mean temperature during the shortest period was 74.17° F. and 
during the longest period it was 70.99° F. These females died in 
from 1 to 7 days after deposition was completed. The average 
number of eggs deposited by the 4 females was 3,210 and the 
maximum number deposited by an individual was 4,555. 
The minimum incubation period under laboratory conditions was 
21days. This record was made during June, 1910. The total effect- 
ive temperature required for embryonic development appears to be 
at least 842° F. The last two lots of eggs, the hatching of which is 
