SEASONAL HISTORY AX I) HABITS. 
23 
During the summer months we have found that all of the seed ( 
hatching from a mass of eggs usually die within one month after 
the first eggs hatch. In one instance a period of 117 days ela] 
between the beginning of hatching of the eggs and the death of the 
last seed tick. This is the greatest longevity which we have observed. 
Table II indicates the variations in the time required for the be- 
ginning of egg laying, incubation of the eggs, and length of time 
required for the starvation of the seed ticks: 
Table II. — Time required for beginning of deposition of eggs, hatching, and 
starvation of .seed ticks of Dermacentor venuxtus. 
Date 
engorged 
female 
dropped or 
was picked 
from host. 
Date first 
eggs were de- 
posited 
Period 
from drop- 
ping of 
female to 
beginning 
of de- 
position. 
Date hatching 
of eggs began. 
Period 
from be- 
ginning of 
deposition 
to begin- 
ning of 
hatching. 
Date 
all seed 
ticks 
were 
dead. 
Period 
from be- 
ginning of 
hatching to 
death of 
last seed 
tick. 
Mean 
daily 
tempera- 
ture dur- 
ing in- 
"ion. 
June 11,1909 
Mar. 28,1910 
Apr. 2,19101 
Apr. .7,1910 
Apr. 13.1910 
Apr. 26,1910 
May l,1910i 
May 14,1910 
May — 1910t 
June 4, 1910 
June 4, 19101 
June 27,1909 
Apr. 7. 1910 
May 13,1910 
Apr. 17,1910 
Apr. 20,1910 
May 2,1910 
May 19.1910 
May 23.1910 
do 
Days. 
16 
10 
41 
10 
7 
6 
18 
9 
July 15.1909 
May 10,1910 
July 3. 1910 
May 19,1910 
May 25.1910 
May 31,1910 
July 9,1910 
June 12.1910 
July 9. 1910 
June 29,1910 
July 21.1910 
Before 
Aug. 10,1910 
Days. 
18 
33 
51 
32 
35 
29 
51 
20 
47 
16 
34 
16 
Sept. 5 
July 25 
Aug. 1 
July 19 
Aug. 15 
July 30 
Sept. 3 
Aug. 31 
Nov. 3 
Sept. 29 
Aug. 11 
Sept. 30 
Days. 
52 
76 
30 
61 
82 
60 
56 
80 
117 
92 
21 
51 
°F. 
91.8 
70.49 
74.6 
71.78 
7LM 
79.04 
June 13,1910 
June 17,1910 
July 25.1910 
9 
13 
9 
84.37 
July 16,1910 
$4.59 
These records were made in the Bitter Root Valley in Montana; all others were made at Dallas. Tex. 
Those larvae which succeed in finding an animal upon which to 
engorge usually attach about the head and ears of the host, be- 
come filled with blood, and drop from the animal between the 
third and eighth days. In nature the larvae feed almost entirely 
upon the small wild mammals, although experiment ally they have 
been forced to engorge upon cattle. As has been stated, the larva' 
after becoming engorged drop from the animal, find a protected 
place, shed their skins, and become active eight-legged creatures 
known as nymphs. These nymphs emerge from the quiescent seed- 
tick stage from about the middle of July to the beginning of cold 
weather. Some of those transforming during the summer find 
hosts, become engorged, and drop for molting. A few of these 
probably molt to adults before cold weather begins and hibernation 
takes place in the adult stage. These few individuals arc the only 
ones which complete their life cycle in a single season. It should 
be emphasized that these nymphs, as well as the seed tick-, feed 
almost exclusively on small wild mammals. Tables III and IV show 
the length of the engorgement and molting period- of larvae and 
nymphs. 
