196 LIFE HISTORY OF NORTH AMERICAN TICKS, 
has continued for a day or so only. Females have been found to 
reattach even when engorged to a considerable extent. Unengorged 
females taken from dogs to which they had attached, and on which 
they had probably mated, engorged as soon as 5 days. Nine days 
was the shortest period in which previously unattached females 
engorged. Morgan, however, states that females engorge in from 
5 to 8 days. 
During engorgement the females constantly excrete what appears 
to be undigested blood. The adults also void considerable excre- 
ment soon after molting from nymphs. 
A male which, with a female, was placed upon an ox November 1, 
1907, remained upon the host, frequency changing its position, al 
eerie 14, when it was fn attached but dead. Thus it remained 
_ upon the host for 105 days from its attachment and 91 days after the 
female had dropped engorged. Other males have disappeared from 
the host on the eighth day after the females dropped. 
TABLE XCV.—Engorgement of females of Dermacentor variabilis. 
Females Period 
Adults applied. Host. dropped of attach- Size engorged. 
engorged. ment. 
Days 
INO Vice O07 se sedece case poe a aes an NS el INGVe Woes ee 14 | 13 by 9 by 5mm. 
Mar. 23, 1908s Ss. ec Boh eSe dO eke ae ee Pecos ee 9|12by 9 by 5mm. 
June 19, LOOSE LE So sees ovine (reattached)...) June 24 5 | 13 by 11 by 7 mm. 
Fai diwis Sieiwinie se spite! sere ae OSe a morats aateitalcicete une 25 6 | 13 by 11 by 7.5mm 
12 by 9 by 6.5 mm 
12.5 by 9.5 by 8mm. 
IDO Sean h oreseasenes| steed dOsc22. 5 aasceckeeee June 26 (5).... 7 \413 by 10 by 8 mm. 
13 by 9 by 7 ae 
13 by 10 by 7 
DOs eh cae aee eee Bovine: =..°. 36 -4e ee Jane 2ees sce 8 12.5 by 10 by 7.5 mm, 
Aug. 24, 1908 (slightly Borie (reattached)...| Aug. 30....... 6} 12 by 7 by — mm. 
engorged). 
Ang: 2419088 22 5 Se ee GOss Re Ss ee ares AUG. Obs. Sse 7| 10by 7 by 5mm. 
Apr. LOM90O Ss oe noe: gee Gone: ae ADE: Zi ss csoees 8 | 13.8 by 9.4 by 7.3 mm. 
Sept. Ss: ggg = be Bac eee dot. 2h Seo Se ey Sept. 16s-5225 8 | Fully engorged. 
be rs See ee | eae Co Coie eee ra eer ISIE 0 re Gy me te 9 | Partly engorged. 
Mar. 36, 1910... Re (es Fe MOS wet os HX) 0) 5g 1 Fees are 16 | One-third engorged. 
LIFE CYCLE. 
Larve may live for 335 days; they may engorge as soon as 4 days 
after application to a host and molt as soon as 7 days after dropping, 
a total effective temperature of 306° F. being required for molting. 
Nymphs may live for from 7 to 8 months; they engorge as soon 
as 4 days after attachment and may molt as soon as 16 days after 
dropping. A total effective temperature of about 741° F. appears 
to be required for this transformation. Adults may live as long 
as 233 days; they may engorge in 8 days (5 days ?) and commence 
ovipositing as soon as 5 days after dropping. As many as 7,378 
eggs may be deposited. Embryonic development may be com- 
pleted in 20 days, a total effective temperature of 825° F. being 
required. 
