THE PACIFIC COAST TICK. 181 
which appear in the late summer or fall from overwintered nymphs 
will hibernate before engorging, it will be necessary to continue the 
treatment of the hosts for at least two seasons. Dipping, swabbing, 
or hand picking would probably not be necessary except between the 
first appearance of the ticks in spring and June 15. As has been 
pointed out by Dr. Ricketts, the destruction of the smal] mammals 
which act as hosts for the immature stages would also aid in lessen- 
ing the numbers of the tick. 
THE. PACIFIC COAST TICK. 
Dermacentor occidentalis Neumann. 
The common name of this tick is derived from the fact that it is 
known to occur only in the Pacific coast region of the United States. 
DESCRIPTIVE. 
Adult (Plate XII, figs. 8-12)—Males 2.8 by 1.6 mm. to 4.2 by 2.3 
mm. Females, unengorged, 2.9 by 1.8 mm. to 3.6 by 2 mm.; engorged, 
9 by 6.1 by 3.3 mm. to 11.8 by 7.6 by 5.6mm. Unengorged males and 
females reddish brown, scutum in both sexes well covered with a 
whitish color resembling bloom, somewhat iridescent, interrupted by 
many red punctures; the same color on dorsal side of legs as on 
scutum. Engorged female steel-gray, dorsum with an olive-green 
surface color, which covers the gray except in small spots, thus 
giving a mottled appearance. 
Nymph.—Unengorged, 1.13 by 0.63 to 1.26 by 0.65 mm.; engorged, 
3.10 by 2.16 by 1.11 mm. Color light brown, lateral portions of 
scutum darker, the intestines, which show through, dark brown. 
Capitulum 0.32 mm. long (from tip of palpi to base of emargina- 
tion of scutum); scutum 0.488 mm. long by 0.557 mm. wide. 
Larva.—Unengorged, 0.643 by 0.426 mm.; engorged, 1.316 by 
0.916 by 0.603 mm. Capitulum 0.139 mm. long (from tip of palpi 
to base of emargination of scutum); scutum 0.23 mm. long by 
0.339 mm. wide. Color, unengorged, reddish brown; engorged, 
bluish gray. 
Egg.—Ellipsoidal, amber to brown in color, shining, smooth. The 
maximum size of 10 eggs was 0.517 mm. by 0.402 mm., the minimum 
size 0.502 mm. by 0.387 mm., and the average size 0.51 mm. by 
0.395 mm. 
HOST RELATIONSHIP. 
The host of the type specimen is the deer. As yet little is known 
regarding the hosts of the immature stages. They attach and 
engorge readily upon guinea pigs, rabbits, and bovines. Over 80 
lots of adult ticks, in which the host animal was given, have been 
received from correspondents. The frequency of occurrence on 
