234 



THE ROYAL SOCIETY OF CANADA 



D. variabilis is a three-host tick. The life cycle appears to start 

 in the spring with the adult female and to be carried as far as the 

 nymphal moult during the summer and autumn and the winter is 

 probably passed in this stage, the adults emerging in the spring. 

 Under laboratory conditions Hadwen found that about 210 days were 

 required for adults to issue, reckoning from the time when the gorged 

 mother tick abandoned the host, and without taking into account the 

 variable period of time which the tick may have to wait for a host 

 when unfed. 



Hadwen (1912) found that the females oviposited at the following 

 times: 



Oviposition began 



Eggs hatched 



Aug. 8, 1910. 



21 



22 

 Eggs not hatched. 

 Aug. 26, 1911, 



The complete life cycle of the last mentioned specimens was 

 obtained under laboratory conditions and was as follows: 



Engorged Ç from dog July 6, 1911 



Oviposition began July 16. 1911 Average number of days 



Eggs hatched Aug 26, 1911 



Larva placed on rabbit Feb. 10. 1912 



Came off gorged Feb. 13-16, 1912 



Larvae moulted and nymphs 



emerged Apr. 30 to May 13, 1912 



Nymphs put on rabbit May 9-13, 1912 



Came off gorged May 14-20, 1912 



Adults emerged June 20-27, 1912 



10 

 41 



4è 



84 



6 



35 



180i 



Dermacentor venustus Banks. 



The Rocky Mountain Spotted Fever 

 Tick. 



(PI. II, Figs. 7 and 8; PI. Ill, Figs. 9 to 12). 



In view of the possible occurrence of Rocky Mountain spotted 

 fever in Canada, and the fact that with the exception of a single 

 recorded capture of D. venustus at Kaslo, B.C., no knowledge was 

 available at that time concerning the distribution of this tick in 

 Canada, an investigation was commenced by me in 1911. The 

 Veterinary Director General of the Department of Agriculture, Dr. 

 J. G. Rutherford, C.M.G., most kindly assisted me by sending to all 



