436 SANITARY ENTOMOLOGY 



species of importance. The species are most abundant in Africa where 

 several of them are connected with the transmission of disease. R. appen- 

 diculatus Neumann is the principal transmitting agent of East Coast 

 Fever, a malignant disease of cattle in Africa, and four other related 

 species play some part in the dissemination of this malady. R. evertsi 

 Neumann is credited with the transmission of Nuttallia equi, or biliary 

 fever of equines, in South Africa. R. bursa Canestrini and Fanzago trans- 

 mits Babesia ovis of sheep in southern Europe and J?, sanguineus 

 (Latreille) Koch, a species which is present in extreme southern Texas 

 and Florida and generally distributed throughout the tropical parts of 

 the world, plays some part in the transmission of babesiasis or malignant 

 jaundice of dogs. The biologies of the ticks in this group are quite simi- 

 lar to that outlined for Ixodes and need not be repeated. With most 

 species the molts are passed off the host. R. bursa, the sheep tick, and 

 R. evertsi, the horse tick, of South Africa, are exceptions, the larval 

 molt being passed on the host and the nymphal molt on the ground. Fbr 

 the most part, the ticks of this group are general feeders. 



The Genus Amblyomma. — This group reaches its maximum develop- 

 ment in South America. In the United States we have three species of 

 some economic importance. The Lone Star tick, A. americanu/m Linnaeus, 

 is the commonest of these. It is widely distributed through the country 

 and extends into South America. The females are readily recognized by 

 the single white spot on the scutum, from which the common name is 

 derived. All of our species are general feeders and attack man freely 

 but are not known to carry disease. In tropical America, A. cajennense 

 Fabricius is tremendously abundant and is often the cause of much annoy- 

 ance to man, the larvae and nymphs attaching to the skin by the hundreds 

 and frequently ulcerated sores develop from scratching. The best known 

 species of this group all drop from the host to molt. Engorgement of 

 the different stages is comparatively rapid, ranging from three days to 

 three weeks. The Bont tick, A. hebraeum Koch, a South African species, 

 is capable of carrying the disease known as heart water of sheep. Louns- 

 bury's studies indicate that the organism of this disease does not pass 

 through the egg but is taken up by the larvag or nymphs and subse- 

 quently transmitted by the following stage. 



The Genus Dermacentor. — This group reaches its highest develop- 

 ment in North America. About half of the species drop from tlie host 

 to molt while the others pass the molts on animals. The most important 

 species economically is the Rocky Mountain spotted fever tick, D. venustus 

 Banks (or D. amdersoni Stiles of many authorities ^). This species drops 



''The editor has chosen to adopt andersoni as the name for the Rocky Mountain 

 spotted fever tick on the grounds of prioritjr and absolute Identification. (See footnote 

 on this species in Chapter XXIX, p. 409. — W. D. Pierce. 



