G. H. F. Nuttall 
425 
being maintained at room temperature in semi-darkness in bottles. 
From the data given in the protocols, the shortest time required for 
the completion of the life-cycle would be 80 days, but this period is 
doubtless considerably prolonged under natural conditions. 
The part played by D. reticulatus in pathology is referred to on p. 422. 
DERMACENTOR VENUSTUS. 
The ticks to which the following record relates were (N. 1731) received 
from Dr C. Gordon Hewitt, Dominion Entomologist, Central Experiment 
Farm, Ottawa, Canada, 22. vii. 1912. The parent females were collected 
from horses imported into British Columbia from Yakima, State of 
Washington, U.S.A., in v. 1912. The females began to oviposit 9. vi. 
1912, and larvae had emerged from the eggs when they arrived in 
Cambridge. 
[The first to raise this tick experimentally was Ricketts* in 
connection with his investigations upon Rocky Mountain Spotted 
Fever, wherein he showed that it transmits the disease. The 
biology of the species has also been studied by Hunter and Bishopp 
(17. XI. 1911, pp. 20-29) in Texas in conjunction with W. V. King 
in Montana. I am much indebted to Dr M. B. Maver, who colla¬ 
borated with the late Dr Ricketts in Chicago, for a personal 
communication received in May, 1912. dealins: briefly with the life- 
history of a strain she had received from Montana and of which 
she sent me specimens now in my collection. Ricketts’ reports 
relate to experiments with different species of Dermacentor and deal 
chiefly with medical matters; his data relating to the biology of 
the tick are somewhat obscure owing to his including several species 
in bis experiments. * Some data, contained in the paper b}' Hadwen 
{Parasitology, vi. 283-297), are included in the summary at the 
end of this section; this author’s observations were made in 
British Columbia. 
The following account of the life-history of D. venustus is based 
on the observations of Hunter and Bishopp^ and of Maver^, whose 
authority for the various statements is indicated in the next 
paragraph by reference numbers. The periods required for feeding, 
metamorphosis, etc., given by Dr Maver, are average periods based 
on many observations. 
Ricketts’ papers are cited in Ticks Bibliograjihics 1 and II, q.v. 
