The evidence indicated that the tick suffers from a relatively harmless, generalized infection and the virus proliferates in its body. The disease probably is transferred through the salivary secretion of the tick since inoculation experiments show that the salivary glands of the infected adult contain the virus. It is probable that in nature the reservoir of the virus of spotted fever is some one or more of the native small animals. Infected ticks have been found in nature, and as various wild animals are susceptible to the disease, it is obvious that it may exist among them unnoticed. Wilson and Chowning suggested that the ground squirrel plays the principal rôle. Unfortunately, much confusion exists regarding the correct name of the tick which normally conveys the disease. In the medical literature it is usually referred to as _Dermacentor occidentalis_, but students of the group now agree that it is specifically distinct. Banks has designated it as _Dermacentor venustus_ and this name is used in the publications of the Bureau of Entomology. On the other hand, Stiles maintains that the common tick of the Bitter Root Valley, and the form which has been collected by the authors who have worked on Rocky Mountain spotted fever in that region, is separable from _D. venustus_, and he has described it under the name of _Dermacentor andersoni_. Mayer (1911) has shown experimentally that spotted fever may be transmitted by several different species of ticks, notably _Dermacentor marginatus_, _Dermacentor variabilis_ and _Amblyomma americanum_. This being the case, the question of the exact systematic status of the species experimented upon in the Bitter Root Valley becomes less important, for since _Dermacentor occidentalis_, _Dermacentor venustus_ and _Dermacentor andersoni_ all readily attack man, it is probable that either species would readily disseminate the disease if it should spread into their range. Hunter and Bishop (1911) have emphasized the fact that in the eastern and southern United States there occur several species which attack man, and any one of which might transmit the disease from animal to animal and from animal to man. The following species, they state, would probably be of principal importance in the Southern and Eastern States: the lone star tick (_Amblyomma americanum_); the American dog tick (_Dermacentor variabilis_); and the gulf-coast tick (_Amblyomma maculatum_). In the extreme southern portions of Texas, _Amblyomma cajennense_, is a common pest of man.