G. H. F. Nuttall 
117 
takes place : from egg to larva in 32-65 days at 17-19° C. ; from larva 
to nymph in 4-6 days at 30° C., in 21-41 days at 15-17° C., in 60-75 
days at 13-14° C.; from nymph to adult in 10 days at 37° C., in 21-28 
days at 20° C., in 64 days at 14° C. Temperature therefore markedly 
influences the rate of development. Oviposition commences 6-23 days 
at 17-19° C. to 50-61 days at 12° C. after the female abandons the 
host, the process lasting 15-56 days, during which period the female 
lays 3000-5770 eggs. Unfed larvae and nymphs were still lively after 
333 days and 164 days respectively in a tightly corked bottle maintained 
at room temperature in a darkened cupboard in the laboratory. Unfed 
adults were lively after 181 days on moistened earth in a gauze covered 
jar kept in the cupboard ; we have one lot of which a few individuals 
were living (unfed) after 630 days, a single male being still alive after 
682 days (21. lii. 13). 
The minimum time required for this species to complete its life 
cycle, judged from the data contained in my protocols, would be about 
147 days, as follows : 
From time egg is laid to emergence of larva ... 
Time required 
in days 
32 
(Eggs at 17-19° C.) 
Larva hardens 
7 
Larva stays on host 
3 
* 
Metamorphosis: Larva to Nymph 
21 
(Larvae at 17° C.) 
Nymph hardens 
7 
Nymph stays on host ... 
5 
Metamorphosis; Nymph to Adult... 
21 
(Nymphs at 20° C.) 
Adult hardens 
7 
Adult $ stays on host ... 
6 
Gorged $ drops off host and waits before laying 
6 
From time egg is laid to emergence of larva ... 
32 
(Eggs at 17-19° C.) 
147 days 
In concluding this paper I have pleasure in acknowledging the 
very valuable aid I have received from my Laboratory Assistant, 
Mr B. G. Clarke, who has been indefatigable and conscientious to a degree 
in connection with all the details of the practical work of raising the 
ticks. The amount of labour and attention involved in raising ticks and 
keeping accurate protocols can only be grasped by those who have 
attempted it themselves. Were it not for Mr Clarke’s enthusiasm for 
the work and his care in matters of detail I should not have been 
able to publish the results which are incorporated in this paper. 
The expenses of these investigations are being partly defrayed with the aid of a grant 
from the Government Grant Committee of the Eoyal Society. 
