THE PACIFIC COAST TICK. 189 
found to remain unattached for 4 or 5 days, some of these dying in 
the meantime. The females which became detached before becom- 
ing fully engorged, as indicated in Table LX X XIX, were undoubt- 
edly dislodged by the rubbing of the host. The shortest period in 
which females were known to become fully engorged was 6 days; the 
longest period was 17 days. In the last instance the female was only 
two-thirds engorged when she was detached. 
LIFE CYCLE. 
A period of at least 105 days elapsed between the beginning of 
hatching of the eggs deposited by a female and the death of the last 
larva. The larvee may engorge in 3 days after attachment and in 
summer molt as soon as 6 days after dropping. The transformation 
from larvee to nymphs requires a total effective temperature of 263° F. 
Nymphs may live at least as long as 76 days during cool weather; 
they engorge as soon as 4 days after attachment and may molt as soon 
as 13 days after dropping. The molting period for nymphs which 
become males and those which become females is practically the 
same. A total effective temperature of 636° F. is required to pro- 
duce this molt. Adults may live as long as 359 days. Females may 
engorge in 6 days, commence depositing in 4 days after dropping, 
and deposit as many as 4,555 eggs. The eggs hatch as soon as 21 
days after deposition and appear to require a total effective tempera- 
ture of about 842° F. for incubation. 
This tick has been found to occur in nature at all seasons of the 
year. The adults appear to become most numerous during the rainy 
season. Many engorged females are to be found on hosts during 
December. 
ECONOMIC IMPORTANCE. 
Owing to the fact that this tick frequently attacks man and often 
occurs in great abundance on domestic live stock, it is of considerable 
economic importance in California and Oregon. Its presence through- 
out the entire season in greater or less numbers also increases its 
importance. Where it occurs it is usually spoken of as the ‘wood 
tick.”’ In central and western California and western Oregon it is 
the most common tick which attacks man. A number of cases have 
been brought to our attention where the bite of this tick has caused 
considerable local inflammation which, in some cases, has required a 
physician’s attention. It is quite common for the rostrum to be 
broken off when the ticks are removed and in such cases the irrita- 
tion and itching usually persists for several weeks. 
Although numerous authors have used the name Dermacentor 
occidentalis in connection with Rocky Mountain spotted fever, 
it is doubtful if this species is concerned in the transmission 
