THE AMERICAN DOG TICK. 195 
The shortest period of engorgement recorded in our observations 
was 4 days. The last nymph to drop left the host on the eighth day. 
TaBLE XCIII.—Engorgement of nymphs of Dermacentor variabilis. 
Nymphs dropped engorged—days following 
application. Total 
Date nymphs applied. Host. number 
| dropped 
1 2 3 | 4 5 6 | 7 
SS ii? ihn Soy i i a a as red ee ee 
Re I Oe Bovine....| 0 0 0 iy ee 1 1 1 | 5 
Oss at a TAT i ae 0 0 0 4 | 1 0 0 0 5 
Engorged nymphs which dropped September 1 commenced to 
molt on the seventeenth day. One nymph which dropped August 
28, 1909, molted on the sixteenth day after dropping. During this 
period the maximum temperature was 101° F., the minimum 78.5° F., © 
the average daily mean 89.3° F., and the total effective temperature 
740.8° F. 
TaBLE XCIV.— Molting of engorged nymphs of Dermacentor variabilis. 
Engorged nymphs molted—days following 
dropping. 
s Number molted. 
Date engorged nymphs Host. 
ropped. 
| 16] 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 3 
2 -|3 = 
s|2| 3 
Zz Sile| « 
0 ae |) Rabbit l... 2) of of o| of oO} o| Oo 0 o}19]....] 1 1+ 
Bont. 10.) 85.2.2 Bovine.... 5} OIF 1d) 19} 29] OF OF O OF O 2 3 5 
LS) Ses ie 2] d1s}1g} 0} Of Of O OF OF O 2 0 2 
ee | ee Bess. 1] Of 0/19] Of OF Of O O OF O 9 1 1 
Sant. 4 1007.22 | ae 1} oF O19] of Of Of OF OF Oo] O OF 1 1 
Aug. 28, 1909...........- Squirrel... 119] Of 0 of 8 O OF OF OF O O 1 1 
PS Gere ar eee | fae, es OD |---| OS ae aa) ust 
1 Collected from a swamp rabbit. 
The adult (Table XCV).—The maximum adult longevity observed 
by us was 233 days. This record was made on a single female which 
became adult September 13, 1909. A female which was collected on 
an opossum May 10, 1910, lived 202 days, and one male in a lot con- 
sisting of 2 males and 3 females, which were collected on a squirrel 
April 6, lived 106 days. Other lots of collected individuals lived 
from 15 to 93 days. If a large number of freshly molted individuals 
were kept for longevity tests without allowing them to feed it is 
probable that some individuals would be found to live longer than 
any observed by us. 
In our observations mating has been preceded by a period of feed- 
ing of from 3 or 4 to 10 or more days after attaching to a host and 
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