[HEWITT] CANADIAN TICKS 237 



presence in western Canada and the danger of the introduction of 

 infected ticks on mammals are questions of no Httle importance. 

 So far as my own inquiries are concerned no evidence has been obtained 

 of the presence in Canada of any cases of this disease. Since 1912, 

 however, reports have been received of the occurrence of the bites 

 of this species causing petechial outbreaks on the body and paralytic 

 symptoms in children.^ Had wen (1913) reported the occurrence of 

 "Tick Paralysis" in sheep in British Columbia. The occurrence 

 of this paralysis in man was investigated by Todd, who published a 

 preliminary account of the results of his enquiry in 1912. In 1914 

 Todd communicated to this Society a more complete account of his 

 inquiries and of experiments which he had carried on, which account 

 he has since published and it constitutes the most complete record 

 we have of this peculiar trouble. Nuttall (1914) has also collected 

 further records. These papers bring together practically all the evi- 

 dence regarding the occurrence of paralytic symptoms in man, sheep 

 and dogs resulting from the bites of this species and this evidence 

 therefore need not be reviewed here. The evidence shows that more 

 than one species of tick may produce these paralytic symptoms and 

 that D. venustiis is able to produce paralysis in lambs and in a puppy 

 under laboratory conditions. A case was brought to my notice of the 

 production of temporary paralysis in a child in Nelson, B.C., by D . 

 veniistus from which paralysis the child recovered, as is usually the 

 case, after the removal of the tick which was attached to the back 

 of the neck. This temporary paralysis which is reported to prove 

 fatal if the tick is not removed, is distinct from the paralysis character- 

 istic of acute poliomyelitis. 



Summary of Life .Cycle of D. venustus. 



Experiments of the life-history of this species were begun in 1912 

 but an accident in my laboratory and absence in England prevented 

 any satisfactory progress being made beyond obtaining data on the 

 oviposition and length of egg stage. Fertile eggs, however, were 

 forwarded to Prof. Nuttall who succeeded in rearing the adults (see 

 Nuttall, 1915). The following account is based on the investigations 

 of Hadwen (1913), Hunter and Bishopp (1911) and Nuttall {I.e.) and 

 my own fragmentary records: 



D ermacentor venustus requires three hosts upon which to feed in 

 the larval or nymphal and adult stages. These stages remain on 



^Ann. Rep. Dominion Entomologist, Year ending March 31, 1913, in Rept. 

 Dominion Experimental Farms, Dept. Agriculture, Ottawa, p. 512. 



