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, frequently changing its position, until 
February 14, when it was found 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 
INOW,-11 1907. «sa cece Bovine Sees sae eece INOve bicep 14 | 13 by 9 by 5mm. 
Mar 23. 108s caf 1a eaan 3| sewers COSece ose Sac eee ies De scones 9 | 12 by 9 by 5mm. 
June og 1903 sch er bas ifovine\Geattactied).. June 24 5 | 13 by 11 by 7 mm. 
bi dadsinc atic nejseicel ae asedOsaceswiass someones JUNC Zee cee oe 6 | 13 by 11 by 7.5mm. 
12 by 9 by 6.5 mm. 
12.5 by 9.5 by 8mm. 
DOs sso toet eiosscscc|ecsce Gos toss foccaeeesee June 26 (5).... 7 {13 by 10 by 8 mm 
13 by 9 by 7mm 
13 by 10 by 7 mm. 
1D es Sser ear Soecocce BOWING. 252 csc esee ce cos June 27........ 8 | 12.5 by 10 by 7.5mm, 
Aug. 24, 1908 (slightly | Bovine (reattached)...| Aug. 30....... 6 | 12 by 7 by —mm. 
engorged). 
PAN P Da OUR Coe cee = cl ea oe COBRER RAE ono ccrase JANIE Blas sate oe 7| 10 by 7 by 5mm. 
Apr. 19, he ae oe ee GOs semen oneeatae PAU Ais ctses- 8 | 13.8 by 9.4 by 7.3 mm 
Sept. 8, 11" a ne ea 6 (0 Be nea Sept..16:: 2... 8 | Fully engorged. 
DG ee eee cccktess see doles. see Bepeswdcccesee 9 | Partly engorged. 
Mar 726; 09102-22220 Seearse. CORE saaarperanesee oN, 0) pi eee 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. 
