200 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 6 



ADDITIONAL NOTES ON THE BIOLOGY OF THE ROCKY 

 MOUNTAIN SPOTTED-FEVER TICK^ 



By F. C. BiSHOPP and W. V. King 



The Rocky Mountain spotted fever problem is becoming familiar to 

 most entomologists, although until the last few years it was generally 

 considered a medical problem. The splendid work of the late Dr. 

 H. T. Ricketts during 1906 and the three succeeding years, which 

 clearly showed that the tick, Dermacentor venustus, is the carrier of the 

 disease, greatly stimulated the interest of entomologists in this field. 

 As was first indicated by Dr. Ricketts^ and later clearly outlined as a 

 result of investigations conducted by the Bureau of Entomology^ in 

 cooperation with the Montana Experiment Station,^ the combatting 

 of the disease resolves itself into a fight against the transmitting agent. 



The problem should not be considered a local one. In the Bitter 

 Root Valley in Montana, where the disease occurs in its most virulent 

 form, from 70 to 80 per cent of the ten to twenty eases which occur 

 there annually result fatally. In Idaho alone, at least 375 cases oocur 

 each year, according to Dr. E. E. Maxey. The death rate in Idaho is 

 much lower but the sIoav recovery of many of the patients adds mate- 

 rially to the economic loss. Hunter and Bishopp have estimated the 

 total number of cases which occur annually in the United States at 

 750 with seventy-five deaths. The disease is not prevalent through- 

 out all of the tick-infested territory but is known to occur in Alaska, 

 Washington, Oregon, California, Nevada, Utah, Wyoming and 

 Colorado in addition to Montana and Idaho, and it probably occurs 

 also in British Columbia. 



The authors desire to acknowledge the helpful suggestions of Mr. 

 W. D. Hunter and Prof. R. A. Cooley under the general direction of 

 whom this work has been done. Professor Cooley is responsible for 

 the observations made on longevity in the Bitter Root Valley during 

 the spring of 1912. The assistance of Mr. H. P. Wood in conducting 

 experiments and making observations at Dallas, Texas, is also grate- 

 fully acknowledged. 



Seasonal Activity of Adults 



Since the adult tick is with rare exceptions the only stage which 

 attacks man and since the most feasible control measures consist of 



1 Published by permission of the Chief of the Bureau of Entomology. 



.2 Spotted fever report Nos. 1 and 2 — 4th Bien. Rept. St. Bd. Health, Montana, 

 pp. 87-191, 1909. 



'W. D. Hunter and F. C. Bishopp — The Rocky Mountain Spotted Fever Tick — • 

 Bull. 105, Bur. of Ent., U. S. Dept. Agr., 1911. 



^R. A. Cooley — Tick control in relation to the Rocky Mountain spotted fever — 

 Bull. 85, Mont. Exp. Sta., 1911. 



