April, '13] TOWNSEND: VERRUGA AND TICKS 217 



range and maintain themselves on man alone, then man constitutes 

 a secondary reservoir to be feared, for the disease is bound to spread 

 wherever the transmitter is aljle to carry it and maintain itself. This 

 is the case with plague, which is transmitted from man to man by fleas 

 that can maintain themselves on man. If, as is probable, the native 

 fauna of, any country ever constituted the primary reservoir of yellow 

 fever and malaria, the fact is of little practical importance today, since 

 infected man is now the prevalent and effective reservoir, whether 

 primary or secondary, of these diseases, which are able to spread and 

 become epidemic wherever their mosquito-transmitters can maintain 

 themselves and infected subjects are present. 



The fact that verruga is not spread throughout the • coast region 

 of Peru by the eruptive phase cases of the disease that are continually 

 arriving therein from the verruga districts indicates beyond doubt 

 that neither the fleas nor the mosquitoes of the coast region are able 

 to transmit it. There are no mosquitoes nor fleas in the verruga dis- 

 tricts that can not maintain themselves equally as well in certain 

 similar districts known to be uninfected. There seems to be no rea- 

 son why the native reservoir fauna of the verruga districts should 

 not maintain itself in certain similar districts at present not infected. 

 There is a possibility that both the reservoir fauna and the transmitter 

 exist outside the actual verruga districts, but that the reservoir fauna 

 is infected at present only in those particular districts. In this case, 

 however, the transmitter must be such that its infected individuals 

 can not spread, either on man or independently of him, from one 

 similar district to another, for otherwise it would infect either man or 

 the reservoir fauna, or both, in the uninfected districts invaded by it. 



Fleas and mosquitoes can and undoubtedly do spread between 

 these very similar deep-quebrada districts of the western Andean slopes 

 and foothills, and they are therefore excluded as possible transmitters 

 of verruga, for the disease does not spread with them. Buffalo gnats, 

 horse flies, stable flies, and all other bloodsucking Diptera are likewise 

 apparently to be excluded for the same reason. There are no dipterous 

 forms present in the region that can in any way be likened to the 

 tsetse flies with their local and zonal distribution dependent on pres- 

 ence of suitable conditions for their development. The conditions that 

 exist in actually infected verruga districts are practically duplicated 

 in many uninfected districts easily accessible to all bloodsucking dip- 

 terous forms present in the former. 



Bedbugs, lice and all other bloodsucking hexapods are likewise 

 excluded for the same reason as given above, while most of them are 

 further excluded because they do not attack the native fauna. More- 

 over, all strictly day-biting bloodsuckers of man are excluded, because 



