202 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 6 



nation in the spring. The question of the relation of climate to this 

 tick will be treated more fully in a subsequent paper. 



The date of the disappearance of adults is much more variable than 

 is the time of beginning emergence from hibernation. The greatest 

 abundance of adults occurs during April and May. During June the 

 number rapidly diminishes so that by the first of July very few spec- 

 imens are to be seen attached to hosts. During the warm summer 

 days, especially toward the latter part of summer, the adults begin 

 leaving the plants upon which they rest while awaiting hosts, and 

 crawl down beneath the grass and leaves. These ticks may be aroused 

 and will occasionally attach, although after August 1 they seem 

 extremely reluctant about feeding and endeavor to escape from the 

 host when applied. In about thirty tests of attachment made after 

 August 15, in but three cases were specimens induced to attach to hosts, 

 and none of these engorged or copulated. 



At high altitudes the activity of adults is continued to a later date 

 in summer than at low^er ones. For instance, at Virginia Dale, 

 Colorado (altitude 7,200 ft.) on June 24-25, 1910, a consideral^le num- 

 ber of ticks, some of which were well engorged, were taken on horses 

 and cattle, while at altitudes of 5,300 feet no specimens were to be 

 found on hosts. A similar condition was observed in the Bitter Root 

 Valley on July 9, 1911, when numerous unengorged adults were found 

 on our clothing above Lake Como at an altitude of from 5,500 to 6,500 

 feet, while in the Valley proper at an altitude of 3,000 to 4,000 feet 

 very few specimens were seen. 



The last adults observed during the investigations of 1910 in the 

 Bitter Root Valley were seen on hosts July 16. In 1911 straggling 

 adults were active to a much later date, the last being observed on 

 August 21. This difference may be accounted for by the much 

 warmer weather which occurred from March to July, 1910. The 

 mean temperature during each month of this period was from 2°F. to 

 8.2°F. above normal, making a total accumulated temperature above 

 the normal of 24.2°F., while in 1911 the mean temperature from March 

 to July was exactly normal, July being below normal. 



In 1911 the last adults were seen on the following dates at the 

 different points: Florence, Mont., August 21; Darby, Mont., July 

 9 (no subsequent examinations); Viewpoint, Oregon, September 25; 

 White Pine, Mont., September 31 ,(no subsequent examination). 

 In 1912 the last adults were seen at Virginia Dale, Colo., August 31 

 and at Viewpoint, Oregon, September 9. The late occurrence of 

 adults at Viewpoint, Oregon, may be due to the comparatively low 

 mean temperature during the summer months, as well as the absence 

 of very high maxima. 



