Biology of Dermacentor 
TABLE VI ( continued). 
Last nymph moulted. 
First mating observed (1 pair). 
Several pairs noted, spermatophore found. 
First engorged female dropped off. 
At least 17 engorged females dropped off. 
At least 4 dropped off. 
8 dropped off. 
5 dropped off. 
At least 4 dropped off. 
1 dropped off. 
1 dropped off. 
1 female (J engorged) dropped off during examination. No other 
females found. 
A total of 24 males present. 
A few males attached. Host has been rubbing ticks off. 
No more ticks found. 
Infestation No. 12. On bovine. 
About 1000 larvae put on bull. 
Very few larvae found. None as large as on horse. 
1 larva moulted (dead). 
First nymph moulted (c?). 
A few of both sexes found. Infestation very light as compared 
with horse (Infestation No. 11). 
1 nymph found. 
No ticks found. 
No ticks observed since last date. 
1 unengorged female found. 
Female gone; no other ticks seen. 
1 male found. 
No ticks found on date nor subsequently. 
Economic Importance. 
D. albipictus has been considered of little or no economic importance 
until very recently. During these investigations we have found the tick 
to be an important pest of horses and cattle during the autumn, winter, 
and early spring. The tick is much more severe on horses than cattle, 
mainly owing to the preference shown for the former animal as a host. 
Reports have been received from California, Montana, and Oregon 
stating that horses and colts become very weak and that colts not in¬ 
frequently succumb if the ticks are not promptly killed. During the 
spring, in territory infested by the Rocky Mountain spotted fever tick 
(.Dermacentor venustus), the combined attack of these two species, to¬ 
gether with a shortage of feed, often causes the death of numbers of 
horses where they are not properly cared for. 
178 
Mar. 25 (29th day). 
,, 26 (30th day). 
,, 27 (31st day). 
,. 30 (34th day). 
,, 31 (35th day). 
Apr. 1 (36th day). 
„ 2 (37th day). 
,, 3 (38th day). 
,, 4 (39th day). 
,, 7 (42nd day). 
,, 8 (43rd day). 
,, 10 (45th day). 
,, 14 (49th day). 
,, 22 (57th day). 
,, 25 (60th day). 
1913 
Feb. 25 
Mar. 4 ( 7th day). 
,, 8 (11th day). 
,, 19 (22nd day). 
,, 22 (25tli day). 
,, 24 (27th day). 
„ 26 (29th day). 
Apr. 1 (35th day). 
,, 2 (36th day). 
,, 5 (39th day). 
,, 14 (48th day). 
,, 16 (50th day). 
