102 



they rest while awaiting hosts, and crawl down beneath the grass 

 and leaves ; in fact after the beginning of August they seem very 

 reluctant to feed. In higher altitudes their activity is continued 

 to a later date. Hibernation may take place in either the larval 

 or adult stage. 



The mountain goat possibly serves as a reservoir for the virus of 

 the disease and infected ticks in the immature stages may be 

 carried by small wild animals, the ground squirrel (Citellus 

 rolumbiamis) and the woodchuck (Marmota jiax'iv enter) , from 

 the higher altitudes to the lower regions where cattle graze. 



Experiments showed the maximum longevity of larva to be 

 317 days and of unfed nymphs 376 days, whilst adults are capable 

 of living more than 641 days. In the Bitter Root Valley, at any 

 rate, the life-cycle of this tick requires from two to three years to 

 complete, for the adults, under natural conditions, will not 

 become engorged during the same season in which they transform 

 to that stage. 



A number of cases of paralysis have been reported as being 

 produced by Derrnacentor venustus. In nine cases of this trouble 

 a tick was found attached in the hair below the occipital 

 prominence. The symptoms subside rapidly after removal of the 

 tick. The point of attack seems to be an important factor in 

 producing these symptoms. In two instances nymphs have been 

 found attached to man, and the fact is important because nymphs 

 of this species have been shown to be capable of transmitting 

 Rocky Mountain spotted fever. Very few specimens of nymph? 

 have been taken on cattle in the IN'orth-western States. 



Strickland (C.) & Merrimax (G.). Report on rat fleas in Suffolk 

 and North Essex.- — Parasitology, vi, no. 1, April 1913, 

 pp. 1-18, 3 charts. Republished from Forty-first Ann. Rep. 

 of the Local Govt. Board, 1911-12. 



Of a total of 822 rats examined, about three out of everj' four 

 harboured fleas ; the average number of fleas per rat was almost 

 exactly 4, but one rat harboured 105, and several rats had 30 to 

 40 fleas Upon them; rats captured on "model" or well-kept 

 farms, had not fewer fleas upon them than others captured else- 

 where. The rat from which 105 fleas were taken was caught on a 

 " model " farm; the average number of fleas per rat A'aried con- 

 siderably in various groups of parishes (0'6 to 6"5), but there is no 

 explanation of this variation. A definite seasonal variation was 

 observed in the number of fleas per rat and in the percentage of 

 rats infested with fleas ; there was a corresponding variation in 

 the maximum and minimum temperatures in the grass-thermo- 

 meter readings and in the atmospheric humidity; it was not 

 determined exactly to what the closely marked seasonal variation 

 in the average number of fleas per rat was due, but probably the 

 temperature is the more important factor. 



Fifteen species of fleas were found on the rats. CeratoijJiyllus 

 fasciatus gave an average of 2"42 per rat, on adult recently killed 

 rodents. Besides this, about 70 per cent, of the fleas caught on 



