22 
THE KOCKY MOUNTAIN SPOTTED FEVER TICK. 
Table I. — Time required for engorgement of females of Dermacentor venustus 
at Dallas, Tex. 
Adults attached. 
Dates of dropping as 
engorged females. 
Period of 
engorge- 
ment. 
Date. 
Host. 
First. 
Last. 
May 15,1908 
Mar. 19,1910 
Apr. 1,1910 
May 4, 1910 
Mar. 29,1911 
May 29, 1911 ! 
Ox 
May 23 
Mar. 28 
Apr. 12 
May 12 
Apr. 7 
June 3 
June 1 
Mar. 2S 
Apr. 13 
May 17 
Apr. 12 
June 15 
Days. 
8-17 
9 
11-12 
8-13 
9-14 
5-17 
Guinea pig 
Ox 
Ox 
Ox 
Goat 
1 The specimens in this lot were fertilized and slightly engorged when applied. 
After the dropping of the females the males usually remain on 
the host for some time. We have found that they crawl about over 
the animal, reattaching in different places and fertilizing a number 
of different females after one infestation of females has become en- 
gorged and dropped from the host. 
Immediately after leaving the host engorged females endeavor to 
find some protected place in which to deposit their eggs. As has 
been stated, deposition may begin as soon as the seventh day after 
dropping, and all of the eggs, which usually number about 4,000, 
are deposited within 30 days. During the process of egg laying the 
female gradually shrinks in size and death takes place within a few 
days after all of the eggs have been laid. The length of time before 
the beginning of egg laying depends largely upon the temperature. 
During cool weather a period of 41 days has been known to pass 
after dropping before the first eggs were deposited. 
The development of the seed tick begins within the egg as soon as 
it is deposited. After the embryonic tick has grown for about two 
weeks, a small white spot appears on one side of the egg. The 
appearance of this spot enables one to determine whether the eggs 
will hatch. The time required for incubation is largely dependent 
upon temperature conditions. In the Bitter Root Valley Mr. W. V. 
King has determined that this period ranges from 34 to 51 days, 
the longer period occurring in the early spring months. At Dallas, 
Tex., we have observed eggs to hatch as early as 15 days after they 
were deposited, the longest incubation period observed in that 
locality being 41 days. After the small seed ticks hatch from the 
eggs they usually remain clustered upon the eggshells for a few 
days and then crawl upon any object in their immediate vicinity to 
await a host. In this stage also the front legs are used as feelers, 
and when an animal conies into contact with the seed ticks, these 
immediately catch hold. Naturally during the larval stage, as well 
as during the adult stage, large numbers of the ticks starve before 
finding a suitable host upon which to engorge. The larvae die 
much sooner from starvation than do the other stages of the tick. 
