24 
THE ROCKY MOUNTAIN SPOTTED FEVER TICK. 
Table III. — Time required for molting of seed ticks and nymphs of Dermacen- 
tor venustus. 
Seed ticks dropped 
engorged. 
Date seed ticks 
molted. 
Period 
from 
dropping 
to 
molting. 
Nymphs dropped 
engorged. 
Date nymphs 
molted. 
Period 
from 
dropping 
Date. 
Number. 
First. 
Last. 
Date. 
Number. 
First. 
Last. 
to 
molting. 
1908. 
Apr. 5 
May 17 
1909. 
Aug. 6 
Sept. 1 
1910. 
July 4i 
July 8i 
July 22i 
1911. 
May 22 
23 
15 
7 
56 
Many. 
Many. 
Many. 
110 
1908. 
1 Apr. 20 
May 27 
1909. 
Aug. 13 
Sept. 7 
1910. 
July 18 
July 19 
Aug. 8 
1911. 
May 30 
1908. 
Apr. 24 
May 30 
1909. 
Aug. 16 
Sept. 10 
1910. 
July 25 
...do 
Aug. 11 
1911. 
June 2 
Days. 
15-19 
10-13 
7-10 
6- 9 
14-21 
11-17 
17-20 
8-11 
1908. 
Aug. 6 
1909. 
Sept. 15 
Oct. 3 
1910. 
Mar. 23 
Apr. 14 
July 21 
Aug. 1 
Aug. 19 
17 
5 
3 
2 
13 
1 
6 
12 
1908. 
Aug. 20 
1909. 
Aug. 6 
Oct. 21 
1910. 
May 4 
May 24 
Aug. 1 
Aug. 14 
Aug. 31 
1908. 
Aug. 22 
1909. 
Aug. 7 
1910. 
Mar. 22 
May 23 
May 30 
Aug. 1 
Aug. 16 
Sept. 4 
Days. 
14- 16 
21- 22 
18-170 
42-61 
40- 46 
11 
13- 15 
12- 16 
1 These records were made in the Bitter Root Valley, Mont.; all others were made at Dallas, Tex. 
Table IV. — Time required for engorgement of seed ticks and nymphs of Der- 
macentor venustus. 
Seed ticks applied. 
Date of dropping 
as engorged seed 
ticks. 
Period 
of en- 
gorge- 
ment. 
Nymphs applied. 
Date of dropping 
as engorged 
nymphs. 
Period 
of en- 
gorge- 
Date. Host. 
First. 
Last. 
Date. 
Host. 
First. 
Last. 
ment. 
1908. 
Apr. 2 
July 12 
1909. 
July 28 
Aug. 2 
Aug. 27 
1910- 
July 19i 
1911. 
May 18 
Ox 
1908. 
Apr. 5 
July 15 
1909. 
Aug. 2 
Aug. 7 
Aug. 29 
1910. 
July 22 
1911. 
May 21 
1908. 
Apr. 10 
July IS 
1909. 
Aug. 4 
Aug. 7 
Sept. 3 
1910. 
July 23 
1911. 
May 24 
Days. 
3-8 
3-6 
5-7 
5 
2-7 
3-4 
3-6 
1908. 
Apr. 1 
1909. 
Aug. 13 
Sept. 10 
1910. 
May 24 
Aug. 13 
Aug. 19 
Aug. 172 
Ox 
1908. 
Apr. 5 
1909. 
Aug. 17 
Sept. 14 
1910. 
May 30 
Aug. 18 
Aug. 23 
Aug. 22 
1908. 
Apr. 8 
1909. 
Aug. 18 
Sept. 15 
1910. 
May 30 
Aug. 20 
Aug. 28 
Aug. 27 
Days. 
4-7 
do 
Guinea pig. 
Rabbit 
Guinea pig. 
Ground 
squirrel. 
Guinea pig. 
Guinea pig. 
Rabbit 
Bovine 
Rabbit 
Rabbit 
Ground 
squirrel. 
4-5 
4-5 
6 
5-7 
4-9 
5-9 
1 This record was made by W. V. King in the Bitter Root Valley, Mont. Dropping probably began 
on July 21, or the second day after application. 
2 This record was made in the Bitter Root Valley, Mont. Records not referred to in footnotes were 
made at Dallas, Tex. 
Those larvae which hatch from eggs deposited by females which 
do not find hosts until late in the spring become engorged during 
July and August and do not molt to nymphs until shortly before 
winter. It is thus necessary for the nymphs which appear late in 
the summer to pass the winter in that stage. These nymphs appear 
in the spring shortly -after the emergence of the adult ticks ; that is, 
shortly after the middle of March. They continue to emerge from 
