until the adult stage was reached. This made the work of rearing the ticks by feeding on various appropriate animals in cages, as done by Mr. F. C. Bishopp and Mr. H. P. Woods at Dallas, of great importance. It involved a large amount of expert work and these gentlemen were remarkably successful in bringing the ticks to maturity.

Fortunately the residents recognize ticks when they see them, though they do not distinguish between species and are confused by the disparity between the sexes. Their observations were of some value to us, particularly with reference to the local distribution. Mr. King spent much time interviewing the farmers and learning the practices in the pasturing of stock in the territory infested by ticks. A large amount of time was spent in examining the domestic animals, including the horse, mule, cow, sheep, and dog, and a large number of adult ticks recovered in this way were sent to Dallas in lots designated by number. Special attention was given to an inquiry into the conditions that favor the multipliIcation of ticks. Several species of rodents were kept in cages to afford opportunity for closer observation of the life history of the tick.

THE TICK FAUNA OF THE BITTER ROOT VALLEY.

A total of 717 small wild animals was shot or trapped and examined for ticks. On these, 4,595 ticks were found, of which a large proportion were in immature stages and all but 1,446 belonged to the genus Dermacentor. When the determinations of the ticks which had been sent, numbered, to the Dallas laboratory were returned, we were able to summarize and interpret the notes. was found that six species of ticks occur in the Bitter Root Valley. They are placed in the probable order of abundance as indicated by our notes, as follows:

Dermacentor venustus Banks.

Dermacentor albipictus Packard.

Ixodes texanus Banks.

Haemaphysalis leporis-palustris Packard.

Ixodes kingi Bishopp Ms.

Ixodes angustus Neumann.

It

SUMMARY OF HOST RELATIONSHIPS.

Without going into details as will be done in a later publication after the completion of the present season's work (1911), it may be stated that the following general conclusions are indicated by the information already secured.

Hosts of adults: The adults of Dermacentor venustus are engorged in the valley almost entirely on domestic animals, principally horses and cattle. Sheep and dogs support them to a very much less extent. It is apparent that on rare occasions such animals as the bear, coyote, and deer may drop engorged adults in the valley, but it is believed that the numbers so deposited have very little influence on tick abundance in the valley. Adults of D. venustus were found on small mammals in the valley as follows: on badger (Taxidea taxus) one male, dead when recovered; on snowshoe rabbit (Lepus bairdi), two adults on three of the hosts which were examined at one time and which carried also about one thousand larvae, nymphs, and adults of Haemaphysalis leporispalustris; on woodchuck, one tick which was not attached but crawling over the fur. It is evident that adults do not commonly feed on ground squirrels from the fact that, out of 209 examined by Mr. King, none bore ticks in this stage while a high proportion carried larvae and nymphs.

In the neighboring mountains three mountain goats (Orcarnos montanus) were shot and examined on "goat rocks" above Rock Creek and Lake Como and some 200 adults of D. venustus were found on them, together with large numbers of D. albipictus. Mountain goats do not leave the rocks and descend into the valley and cannot act as carriers of ticks into the valley.

Hosts of larvae and nymphs: None of the immature stages of D. venustus were taken from any of the domestic animals, but they were found in great abundance and apparently without much discrimination on a wide variety of small mammals. So generally do they attack these smaller mammals that it would not be surprising to find that without exception they are all attacked if encountered, They were found on field mice but not on shrews.

Considering the relative abundance of the various hosts of the early stages it can be stated beyond a question that by far the greater part of the larvae and nymphs feed on the columbian ground squirrel, the pine squirrel: Sciurus h. richardsoni), and the yellow-bellied

chipmunk. They are common, however, on a large number of other small mammals, including the woodchuck, rock squirrel, wood rat, and cottontail rabbit (Sylvilagus nutalli). Considering the abundance of these and the other hosts of the immature stages of the spotted fever tick in the valley and the frequency with which they were found to be infested with ticks, it is not difficult to account for the abundant supply of adults for domestic animals.

The writer had previously secured a number of records of the occurrence of Dermacentor albipictus on horses that had been allowed to graze in the open during the winter and early spring. These observations led us to make further inquiry into the occur1ence of ticks on horses during the fall, winter, and spring as reported by Dr. Ricketts and residents of the Bitter Root Valley, and two special trips were taken from Bozeman to the Bitter Root Valley by Mr. King for the purpose of getting information on this point. During the fall and winter months he was able to find nymphs and adults of . albipictus in abundance on horses but neither adults nor nymphs of D. venustus were found. It is believed that D. albipictus nymphs and adults feed only during the fall, winter, and spring, remaining on the host for nymphal quiescence, and that frequent reports of the occurrence of spotted fever ticks on horses in the winter months are based on the presence of this species. CONDITIONS THAT FAVOR THE MULTIPLICATION OF TICKS.

COWS.

It is clearly indicated that the presence of the spotted fever tick in abundance is dependent upon the joint occurrence of a sufficient number of rodents and of domestic animals, principally horses and This appears to be about all there is to "favorable conditions" as spoken of in the valley. It is not clear yet whether or nct open, cleared lands are directly unfavorable to the multiplication of ticks and it is possible that direct sunshine is fatal to the younger stages. It is possible also that the more frequent occurrence of ticks in wooded and semi-open, brush-grown areas is explained by the fact that such tracts are thickly inhabited by rodents and given over to the pasturage of animals. Ticks may often be found not only in cleared pastures but on grassy mountain slopes and in neglected orchards and meadows. It should be noted that the conditions that now prevail in many localities on the west side are certainly very favorable to the continued abundance of ticks.

DISTRIBUTION OF TICKS IN THE VALLEY AS COMPARED WITH THE ADJACENT CANYONS AND MOUNTAINS.

While ticks are more abundant on the west side of the valley they are not confined to that side. It is believed that the principal limiting factors on the east side are the prevalence of open, clear country, which is not so favorable to rodent life, and the smaller number of domestic animals.

The canyons leading out of the valley in the vicinity of the field station are narrow and mostly impassable to horses and cows. Several immature ticks were taken from "rock rabbits" (Ochotona princeps) in one of these impassable canyons. They belonged to the genus Dermacentor but as they died before maturing it is impossible to state the species; it is probable, however, that they were D. venustus. In no case was an adult spotted fever tick taken on an animal found in these canyons or from the clothing worn there, not even in one canyon that has a trail passable to horses. Except in one case no adults were picked up on the mountain slopes near camp more than a short distance from the foot and in this instance the five adults found on the clothing after ascending might have been picked up in approaching the foot of the mountain through the thickly infested areas. However, ground squirrels were found. on a flat that was passed through at an elevation of 5,600 feet and a nymph of D. venustus was recovered from one.

From the observations made it seems very apparent that ticks occur in abundance in the edge of the mountains on the west side, only in areas used by horses and cows for grazing purposes. The mountain slopes are very steep and most of the canyons are inaccessible, resulting in the practical limitation of the grazing animals to the valley, the foothills, and the first slopes.

Adults were found in abundance on "goat rocks" above Lake Como. In a two days' climb on the rock face exposed to the south en the north side of Rock Creek, Mr. Birdseye picked up 100 adults (estimated) on his clothing at an elevation of between 5,000 and 7,500 feet. Out of these ticks 15 were saved and proved to be D. venustus. About 200 adults of this species were recovered from three goats at this place, and others were left on the goats. Small mammals occur here.

These were the only records secured of this species of tick oc

curring in the mountains, though Mr. King and Mr. Birdseye made frequent searches.

From the season's experience, therefore, it is believed that ticks. inay occur in abundance in restricted localities back in the mountains but it is very evident that in general they are scarce there. It is probable that where deer "licks" and other frequented localities overlap the range of small animals ticks may occur. However, at least one such locality was searched without finding ticks.

It should be remembered that ticks probably occurred in the mountains on wild game and rodents before the coming of white men, and that the mountains will always be a source of reinfestation.

SEASONAL HISTORY OF THE TICK.

As the season's work opened up at the field station it early became evident that nymphs were out in abundance and were feeding on rodents. In April, out of 86 ground squirrels examined, 60 bore a total of 441 nymphs. In May, out of 26 ground squirrels examined, 15 bore 196 nymphs. Mr. King King had been in the camp since early spring and was watching for the first appearance of ticks and of animals that might serve as hosts. Ground squirrels began to appear on March 26th and seven were examined before the 1st of April, but none of these carried nymphs, indicating that they came out of their winter nests free of ticks, and that the nymphs found later were picked up in the regular way. A similar experience was had with chipmunks and pine squirrels.

Nymphs continued to be abundant until the latter part of June when there was a gradual reduction in the number, although scattering individuals were found up to September 8th.

It was suspected that these nymphs might belong to some other species of Dermacentor whose adults had not been detected, for it seemed to be difficult to otherwise explain their presence at that season of the year. It was supposed that nymphs would be found only after larvae had appeared from the season's eggs and had had time to feed and mature. It later became evident from the determinations received from Dallas that these nymphs were D. venustus and that another explanation was necessary. Along in August it became noticeable that, notwithstanding the fact that sufficient time had elapsed to produce fresh nymphs in abundance. from seeds that had fed in June and July, the number recovered