170 LIFE HISTORY OF NORTH AMERICAN TICKS, 
to hatch from the first eggs deposited some time before deposition is 
complete. 
Ordinarily larve attach within a very short time after they are 
applied to a host. However, we have observed them to remain 
unattached for three days when kept in close proximity to a host. 
The majority of the larve attach around the head and ears of the 
hosts. They are, however, frequently found on the back, especially 
between the shoulders. Larve when removed from a host when 
shghtly engorged were found to attach to another host several days 
or even weeks later. 
In a number of instances larve which had awaited a host for 
two months were found to attach when placed on a host, but many, 
and in some eases all, died without engorging owing to their weakened 
condition. 
The shortest period required for the engorgement of larve was 
two days. The greatest number drop from the host on the third, 
fourth, and fifth days after attachment. In two cases larve 
remained on the host for 8 days. 
TaBLE LXXVII.—Engorgement of larve of Dermacentor venustus. 
Larve dropped engorged—days following appli- 
cation. 
Date larve applied. Host. thee banshee ae tye Ree meee 
March s0lce cee ee esac ee Bovine. .2.---- 0 0 0 1 2 0 0 0 3 
PERO: Eee S ahs ee. ee dOzsse-5 ces 0 0 23 27 17 13 3 1 84 
MiaVelS Secccec nase ccee acer eres (OOkevcoaese 0 0 0 15 10 0 0 0 25 
DU 85 oe Se was Oe ace eas dois. 2.826 0 0 2 3 0 0 0 0 5 
Uy Ree Po ee sete once al eee COM eceets 0 0 76 64 12 4 0 0 156 
1909. 
Duly 28 UN a ees es eee Guinea pig.... 0 0 0 0 6 2 2 0 10 
Pub y SO ess 2 eS ee Ru AMONG saan 0 0 0 0 6 5 0 0 11 
DOM es Soe See eee Bovine........ 0 0 0 2 1 0 0 0 3 
IAT END Sh 5 ee SE Rabbitss.2 2-2. 0 0 0 0 3 0 0 0 3 
BA ES seers ap ioe rs oye eee Guinea pig 0 0 0 0 2 0 0 0 2 
DO an se aS Se eae Boviness232. 2. 0 0 0 1 2 0 0 0 3 
IE ec aera cs = Soles eee oats (aR See eae 0 0 0 1 0 0 0 0 1 
IDO tres 2 fps Se eee Guinea pig 0 0 0 0 0 1 0 0 1 
UAC AT eee SA tees, See eee doses 0 0 0 0 23 23 2 0 48 
PAIS 27 Sea 5 ee See = ee do 0 13 26 58 56 23 5 0 181 
When the mean temperature was about 83° F. larve were found 
to become quiescent in from 24 to 60 hours after dropping. Immedi- 
ately after becoming quiescent the tick begins to take on a light 
color at the anterior end. 
Larve which dropped September 1, 1909, began molting on the 
sixth day thereafter. This was the shortest molting period observed. 
The mean temperature during the period was 88.29° F. and a total 
effective temperature of 272° F. was accumulated. The longest 
period from dropping to molting observed by us was 19 days. The 
mean temperature during this period was 70.5° F. The effect of 
temperature on the length of the molting period is marked. When 
the mean temperature was about 70° FI’. molting began between 
