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WoLBACH (T, B.). The Etiology of Rocky Mountain Spotted Fever.— 



SndBienn. Rept. Montana State Bd. Entom. 1915-1916, Helena, 15th 

 December 1916, pp. 35-44, 3 plates. [Received 17th April 1917.] 



This paper deals AAath the pathology and occurrence of the parasite 

 of Rocky Mountain fever in guinea-pigs and monkeys and also in ticks. 



Infected ticks were obtained by allowing them to feed once or more 

 upon infected gumea-pigs, their infectivity being subsequently proved 

 by allowing them to feed upon normal guinea-pigs. Ticks shown to 

 be non-infective by feeding once or twice upon normal guinea-pigs 

 were used for controls. It was found that a single feeding frequently 

 failed to render a tick mfective and occasionally two or even three 

 feedings were required in order to do so. The distribution of the 

 parasite in tlie infected ticks mdicates transmission through the 

 saUvary gland secretions. Transmission by faecal contamination of 

 the wound caused by the tick in feedmg does not seem possible, as 

 the faeces collect m the form of small pellets that soon become hard 

 and dry and do not soil the skin of the host. 



No new light has been obtained as to the exact nature of this 

 organism. 



Parker (R, R,). Some Facts of Importance concerning the Rocky 

 Mountain Spotted Fever Tick {Dermacentor venustus. Banks) in 

 Eastern Montana.— 2n(^ Biennial Rep., Montana State Bd. Entom. 

 1915-1916, Bozeman, 15th December 1916, pp. 45-56. [Received 

 17th April 1917.] 



During the season of 191 G a field station was established in Eastern 

 Montana for the purpose of studying the bionomics of Dermacentor 

 venustvs and the economic conditions, the control measures adopted 

 in Western Montana being mapplicable to the Eastern side of the 

 State. The species of ticks found included D. venustus, which is the 

 only agent known to transmit Rocky Mountain spotted fever in nature, 

 Haemaphysalis leporis-palustris, Pack, (rabbit tick), Ornithodorus 

 megnini. Dug., and Ixodes spp. A table is given of 22 wild mammalian 

 hosts, the most important being Lepus townsendi amipanius (jack 

 rabbit) and Erethizon epixanthus (porcupine). Domestic animals 

 recorded as tick hosts are horses, cattle, sheep, dogs, cats and pigs. 

 Only adult ticks are known to occur on these animals, while some of 

 the wild hosts, notably the jack rabbit, are important hosts of the 

 nymphs and perhaps the lar^'ae. 



Notes are given on the life-history of D. venustus under eastern 

 Montana conditions. Oviposition begins in April, adults being most 

 numerous from mid- April to the middle of June. The ticks evidently 

 pass the winter as unfed nymphs and adults. In eastern Montana 

 there are apparently no natural barriers against the spread of ticks, 

 the limit of spread from any given locality being that of the ranging 

 powers or habits of the host animals ; cattle, horses and sheep are 

 the most important agents of dispersal. 



Ticks were common on human beings during the season of 1915 

 and, though less abundant during 1916, the majority of persons were 

 troubled by their presence on the body or clothing at some time or 

 other from March to Ausjust. 



