April, '13] BISHOPP AND KING: SPOTTED FEVER TICK 207 



The shortest period from dropping to molting of larvae observed in 

 1911 was fifteen days, while in 1910, owing to higher temperature, 

 some molted in eleven days. The longest molting period was thirty- 

 one days. This record was made on larvse which dropped from a 

 ground squirrel August 30, 1911. 



An interesting record of the longevity of unengorged nymphs was 

 made in 1910-11. A lot of thirteen nymphs which emerged July 25, 

 1910, were kept in a small vial covered with gauze in a shed in the 

 Bitter Root Valley. On March 14, 1911, all were alive; July 23, ten 

 were alive and active; August 1, four were alive, one being weak, and 

 all were dead August 7. The last survivors had lived one year and 

 eleven days without food. Several other lots lived almost a year. 



As has been mentioned, a lot of engorged nymphs survived the 

 winter of 1910-11. These were engorged between August 22 and 

 September 11. Although kept under rather unnatural conditions, a 

 number of abnormal adults emerged during March, 1911, and twenty- 

 six males and seventeen females, all of which were normal, emerged 

 between July 26 and August 18, 1911. The maximum period from 

 dropping to molting in this series was eleven months and nineteen days. 

 In a large number of records on the molting period of nymphs made 

 in the Bitter Root Valley by one of the authors (King) in 1911, nymphs 

 which dropped, engorged, in April molted from eighty-three to between 

 130 and 140 days later. Those dropped in May molted within 

 seventy-three to ninety-nine days; those dropped in June molted 

 within thirty-nine to sixty -four days; those dropped in July molted 

 within twenty-nine to sixty-one days, and those dropped in August 

 molted within twenty-seven to thirtj^-one days. All nymphs which 

 were engorged by us in the Bitter Root Valley during 1911 molted 

 before the coming of cold weather, except a single specimen which was 

 collected on Julj' 4. This had not transformed by October 16 and was 

 not observed afterward. At Dallas, Texas, however, in a lot of 

 nymphs which dropped from a host October 3-6, 1911, three molted 

 to adults the following year. One of these (a male) emerged on May 

 6, and two (a male and female) emerged shortly before June 8. One 

 nymph in this lot transformed to a male on October 30, 1911, and the 

 others died during the winter. One of those which died remained 

 active for 103 days and another for 136 days after dropping from the 

 host thus showing that transformation proceeded very sloAvly. 



As is to be expected, the longevity of adults is greater in the Bitter 

 Root Valley and other parts of the Northwest where the tick occurs 

 under more natural conditions than at Dallas, Texas, where many of 

 the previously published records on longevity have been made. A 

 series of tests made by one of the authors (King) in the Bitter Root 



