172 
Biology of Dermacentor 
TABLE V. Moulting of nymphs of Dermacentor albipictus 
when removed from host. 
Dates of moulting 
Date 
nymphs 
collected 
Host 
State of 
engorge¬ 
ment 
No. col¬ 
lected 
first 
moulted 
» 
last 
moulted 
Eangein 
moulting 
period 
Number moulted 
males females total 
1910 
Mar. 23 
Horse 
Fully 
1 
1910 
Apr. 5 
1910 » 
13 
0 
1 
1 
„ 28 
99 
1 
„ 12 
— 
15 
0 
1 
1 
Apr. 19 
9 9 
99 
1 
May 1 
— 
12 
0 
1 
1 
Oct. 29 
> J 
1/3 to 
11 
Nov. 26 
Dec. 10 
28-42 
1 
4 
5 
Dec. 24 
9 9 
4/5 
4/5 to 
3 
1911 
Feb. 1 
1911 
Feb. 17 
39-55 
3 
0 
3 
„ 26 
> 9 
fully 
1/2 to 
6 
Jan. 12 
„ 21 
17-57 
0 
2 
2 
1911 
Jan. 7, 8 
9 9 
fully 
1/5 to 
40 
Feb. 17 
Mar. 25 
41-76 
12 
16 
28 
„ 10 
9 9 
fully 
4/5 to 
12 
.. 3 
» 27 
24-76 
2 
10 
12 
Feb. 3 
99 
fully 
1/2 to 
23 
„ 15 
Apr. 2 
12-58 
7 
12 
19 
„ 5 
fully 
4/5 to 
88 
„ 15 
Mar. 30 
10-53 
18 
64 
82 
May 16 
Guinea-pig 
fully 
3/4 
1 
June 6 
21 
0 
1 
1 
Nov. 11 
Ox 
2/3 to 
2 
Dec. 24 
1912 
Jan. 8 
43-58 
1 
1 
2 
1912 
Jan. 11 
Horse 
3/4 
1/2 to 
7 
1912 
Feb. 19 
Mar. 25 
39-74 
0 
4 
4 
25 
9 9 
9 9 
fully 
1/2 to 
7 
„ 19 
Apr. 5 
25-71 
2 
3 
5 
Mar. 23 
9 9 
fully 
Fully 
2 
Apr. 14 
22 
0 
1 
i 
Totals 
205 
46 
121 
167 
stage. A large number of records made on these points at Dallas, 
Texas, show that adults which have never fed live from a few days 
to 140 days, individuals which have fed after moulting but have not 
become perceptibly engorged may live for 182 days, and females 
partially engorged, but not sufficiently so to oviposit, may live for 129 
days. The males are shorter lived than the females, the greatest 
longevity observed being 97 days. The longevity of males on the host 
(together with females) is rather less than when they are removed. 
In our experiments the longest period from the moulting of the first 
male on a host to the death of the last male was about three months. 
The first ticks to reach the adult stage on a host are usually males. 
The females begin emerging from a few hours to a day later. There 
