214 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 1 



to test the popular theory and became convinced that the presence of 

 the cattle-tick was necessary to the transmission of disease. Later, he, 

 with Dr. T. Smith, proved that the tick was an intermediary host of 

 the blood parasite causing the dise&se and in the same year Dr. Theo- 

 bald Smith described the parasite as Pyrosoma bigeminum, now Piro- 

 plasma. The southern cattle accustomed to tick infestation from birth, 

 become immune to the disease, but if not raised in tick-infested fields 

 they are as susceptible to the disease as northern cattle. 



Since 1890 many experiments by various observers have served to 

 confirm Dr. Kilborne's results. Diseases similar to Texas fever occur 

 in cattle in various parts of the world. In South Africa Louusbury 

 has shown that heartwater is transmitted by the "bont tick," Ariv- 

 hlyomma hebrceum. Later he has shown that malignant jaundice in 

 dogs is due to the attack of a dog tick, Haemaphysalis leachi, and that 

 African coast fever in cattle is carried by five species of Rhipicephalus. 

 In each case there are differences in the manner of infection and the 

 stage of the tick capable of infecting an animal, and various peculi- 

 arities in the life history of each tick. 



These discoveries have served to open a wide field of suspicion and 

 investigation, so that during the past few years ticks have been ac- 

 cused of transmitting man}^ different diseases to various animals. 

 The evidence, however, in many cases, is far from conclusive, but, 

 doubtless, as experiments are carried on proof will become established 

 of the culpability of other ticks in the diffusion of disease. 



Louping ill in sheep is thought to be carried by an Ixodes; spiril- 

 losis in fowls is attributed to an Argas; spotted fever due to the pres- 

 ence of a Dermacentor. A disease of turtles is laid up to Hyalomma 

 mgyptium; carceag, an European disease of sheep, is supposedly trans- 

 mitted by Rhipicephalus bursa. An undetermined Ceylonese tick is 

 credited with producing paranghi or "yaws." Infected specimens of 

 Ixodes ricinus have given a piroplasmosis to European cattle ; and the 

 "moubata bug" {Ornithodoros moubata) is the inoculating agent of 

 one of the most dangerous diseases dreaded by inhabitants of West 

 Africa. 



From the known results, it is evident that the power to transmit 

 disease is not confined to any one genus or section of Ixodidce, but 

 common to all. Moreover, in different countries extremely similar 

 diseases are carried by very different ticks. Therefore the diseases 

 have not originated in the ticks. Most, if not all, of the species now 

 acting as agents in the dissemination of disease to certain hosts were 

 probably originally confined to other hosts. To their original or nat- 

 ural host they brought no disease. Certain low organisms living in 



