F. C. Bishopp and H. P. Wood 
183 
periods. The larvae which we have observed were hatched in spring 
and they remained practically motionless, unless disturbed, until to¬ 
wards the fall. No attempts were made to attach larvae to hosts 
during the summer, but it is our opinion, from the actions of the unfed 
larvae, that they would not attach themselves readily to hosts until 
autumn. This is also borne out by the fact that ticks of this species 
have not been collected on hosts during midsummer or early autumn. 
As is shown in Table VIII the greatest longevity of larvae noted 
by us was 166 days. Larvae are capable, no doubt, of living much 
longer than this. 
TABLE VIII. Preoviposition, incubation, larval longevity and 
total non-parasitic period of Dermacentor nigrolineatus. 
Period from Period from 
beginning dropping 
Date Date ovi- Preovi- Date deposition of female 
females 
collected 
position 
began 
position 
period 
hatching 
began 
to first Date last 
hatching larva died 
Larval 
longevity 
to death of 
last larvae 
1911 
1912 
1912 
1912 
(days) 
(days) 
Nov. 11 
Apr. 1 
139 
May 26 
55 
Oct. 7, 100 alive 
134 + 
328 + 
„ 14 
„ 11 
149 
„ 29 
48 
Nov. 8,150 alive 
163 + 
360 + 
» 14 
.. 23 
161 
„ 30 
37 
Oct. 1—Oct. 28 
124—151 
322—349 
Dec. 5 
„ 22 
139 
June 4 
43 
Oct. 30 
148 
330 
„ 11 
,, 11 
122 
May 30 
49 
Aug. 10 
72 
243 
— 
„ 14 
— 
„ 30 
46 
Nov. 12 
166 
— 
— 
„ 14 
— 
„ 30 
46 
Oct. 1 
124 
— 
We 
have found that engorged 
larvae removed 
from a 
host will 
moult to nymphs which are capable of becoming reattached to a host. 
In one instance a larva moulted on the fifth day after it was removed. 
The length of the moulting period of larvae detached from a host is 
dependent largely upon their state of development before removal. 
The period from the attachment of larvae to the beginning of 
moulting (on the host) is about 10 days (see Table X). 
The Nymph (PI. X, figs. 10, 11): After the nymphs escape from the 
larval skins they attach themselves near by. The larval exuviae usually 
remain attached to the host by the mouth-parts for sometime. The 
nymphs are pale yellowish-brown for a period after transformation, and 
are comparatively slow and clumsy in their motions. Fully engorged 
nymphs vary from almost white to slate-coloured. The body is 
elliptical in outline, but sometimes it is broadest at the anterior end. 
The length (including palpi), width and thickness of the average sized 
engorged nymph are about 23, 17 and L0 mm., respectively. 
A nymph which moulted from an engorged larva collected on 
a cow in Tennessee readily attached itself to a calf at Dallas, Texas, 
