F. C. Bisiiopp and H. P. Wood 185 
slightly engorged female in a lot of three females collected December 6, 
1911, lived 209 days. 
Individuals which became adult away from their hosts readily 
attached themselves to a calf and a rabbit. One female had become 
about ^ engorged on the ninth day after attachment, when it was 
detached by the rubbing of the calf. Another female put on a host 
on December 1, 1911, dropped fully engorged on December 11. 
When development proceeds normally on a host, adult engorgement 
appears to require from six to 10 days (see Table X). Copulation 
takes place on the host. The males require a period of three or four 
days’ feeding before mating. The females may be fertilised during any 
stage of their engorgement after a short feeding period. 
TABLE X. The parasitic period of development of 
Dermacentor nigrolineatus. 
1912 
Infestation No. 1. On bovine. 
Sept. 25. 
Oct. 11 (17th day). 
,, 14 (20th day). 
,, 19 (25th day). 
,, 21 (27th day). 
,, 23 (29th day). 
Nov. 1 (38th day). 
About 500 larvae put on bull. 
1 nymph fully engorged. 
No ticks found. 
Another fully engorged nymph found. 
Nymph last observed has just moulted. Another nymph found. 
1 female found. 
Female fully engorged. No other ticks found. 
1912 
Infestation No. 2. On bovine. 
Oct. 7, 8. 
,. 15 ( 8th day). 
,, 19 (12th day). 
,, 23 (16th day). 
,, 25 (18th day). 
Nov. 1 (25th day). 
„ 2 (26th day). 
,, 4 (28th day). 
,, 5 (29th day). 
,, 8 (32nd day). 
,, 9 (33rd day). 
About 500 larvae put on bull. 
A larva fully engorged. 
3 nymphs seen. The largest probably moulted on October 17. 
Some nymphs fully engorged. 
The first nymph moulted ( s ). 
All nymphs have moulted (several since Oct. 29). 
First copulation observed. One engorged female dropped off 
when touched. 
2 females dropped oft'. 
2 engorged females dropped off during examination. 
1 female dropped off. 
2 females dropped off. 
After emerging from the nymphal skin the adult attaches itself 
near the cast skin which remains attached to the skin of the host. Often 
the ticks become detached several different times and crawl about for 
some distance before they begin to show perceptible engorgement. On 
one occasion nearly all the adults, which had begun to engorge, were 
observed to migrate from the shoulders and sides of a bovine to the top 
Parasitology vi 
13 
