79 



tank. No dipping is done until the chemical analysis shows that the 

 correct strength of arsenic has been obtained : kerosene not com- 

 pletely emulsified is carefully removed by skimming. Frequent 

 analyses are made so as to keep the solution in the tank always at the 

 right strength. 



For the destruction of the native rodent hosts of the tick, especially the 

 Columbian ground squirrel {CiteUus columbianns), the following poisoned 

 grain formula gave the best results: to 1 teaspoonful saccharine 

 and 1 pint of salt dissolved in 2|- pints of warm water, one pint of 

 starch is added and the mLxture heated, but not cooked, and con- 

 stantly stirred until quite thick ; 2 oz. powdered strychnine alkaloid 

 are then added to the starch solution and well mixed with it. This 

 mixture is poured over 16 quarts of hulled oats in a tub and well 

 mixed by rubbing through the hands. By means of this formula 

 the grain is given a poisonous coating, the alkaloid of strychnine being 

 insoluble in water. 



It was estimated that at least half the squirrels in the treated 

 area were killed in 1915 by this bait and that a further reduction of 

 50 per cent, was obtained in 1910. 



Fricks (L. D.). Review of the Rocky Mountain Spotted Fever Eradi- 

 eative Work conducted by the United States Public Health Service 

 in the Bitter Root Valley, Montana, 1915-1916.— 2w/ Bienn. 

 Report. Montana State Bd. Entom. 1915-1916. Helena, 

 15th December 1916, pp. 24-27. [Received 17th April 1917.] 



The work of eliminating Eocky Mountain spotted fever from the 

 Bitter Root Valley was continued during 1915-1916 on the plan out- 

 lined by the representatives of the Public Health Service [see this 

 Review^ ^ev. B , iii, p. 62]. Some of these measures have been amplified, 

 more especially in connection with the destruction of small rodents 

 ( and the substitution of sheep for horses and cattle on the west side 

 of the valley. This area is suitable only for grazing purposes and 

 good results " were obtained in tick destruction in the districts under 

 observation. Continued effort has been made towards decreasing by 

 legislation, regulation and substitution, the number of horses and 

 cattle allowed to graze on the west side of the valley. 



Fricks (L. D.). Rocky Mountain Spotted Fever. A Report of Labora- 

 tory Investigations of the V\TUS.~-2nd Bienn. Rept. Montana State 

 Bd. Entom. 1915-1916, Helena, 15th December 1916, pp. 28-34. 

 [Received 17th April 1917.] 



It has been found that man, rhesus monkeys and at least six varieties 

 of small wild rodents found in the Rocky mountains are susceptible 

 to the infection of Rocky Mountain fever, while the larger domestic 

 animals are generally immune. Guinea-pigs and white rats {Mm 

 norvegicus albinus) are highly susceptible, while white mice are appar- 

 ently immune. The virus is transmitted by the bite of infective 

 wood ticks {DerniacentoT venustus), recovery being followed by complete 

 immunitv. No insect or other biting Arachnid has been found 

 capable of transmitting the virus, but a female tick, once infected, 

 remains so and transmits the virus to its progeny. 



