128 0. H. T. TOWNSEND — PROGRESS IN THE STUDY OF VERRUGA, ETC. 



always situated in or near deep narrow canyons, with much vegetation, heat and 

 little ventilation. It is now known that the Phlebotomus flies avoid the wind, the 

 sun, and even the full daylight as well. They appear at sunset, if there is no 

 wind, and enter houses, if the light be not to strong within. Candles and oil 

 lamps attract them, but strong electric lights appear to dispel them. During the 

 day these gnats remain hidden largely within the interstices of rock formations, 

 in loose earth, caves, etc., or amongst rank vegetation out of the light and wind. 

 They suck the blood of practically all warm-blooded animals, and have even 

 been known in Africa to suck the blood from a lizard. Thus they are not at all 

 dependent on man, and the primary reservoir of verruga doubtless lies in the 

 native fauna, as already suggested by the writer. 



Phlebotomus breeds in caves, recesses in the rocks, even in rock embankments, 

 stone fences and walls, showing interstices however small, and minute recesses in 

 newly excavated rock, gravel and earth material. This explains the excavation 

 theory of infection, also the soil theory. The fact that the flies never appear till 

 sunset explains why the Central Railway bridge-building gang in 1909 escaped 

 infection as soon as they began to pass the nights in Chosica. The flies are 

 confined to places sheltered from the winds, which explains the peculiar alti- 

 tudinal distribution of verruga, otherwise to be explained only on the theory of 

 tick or other acarid transmission. The flies doubtless breed most abundantly 

 during periods of moderate humidity. Too much humidity appears to retard 

 their development, as does cold. The winds have little sweep in the narrower, 

 deeper and more tortuous quebradas of the verruga zones, the natural stagnation 

 of the air being especially favourable to the presence of the gnats. The caves 

 and rock conditions necessary to their breeding exist without limit in these 

 canyons, and the vegetation in the bottoms affords them shelter by day or 

 night. 



The close parallelism between verruga and Rocky Mountain spotted fever, as 

 detailed by the writer, loses little of its force except that acarids are less indi- 

 cated in the transmission of the former and the causative organisms of both are 

 probably to be referred to the ultravisible group conveniently termed the 

 Chlamydozoa. 



So far it has not been possible to secure sufficient numbers of the Phlebotomus 

 for experimentation, the season for them being apparently on the wane, but such 

 work will be started at the earliest possible moment. It is most confidently 

 expected that this work will give prompt and positive results in verruga infection. 

 Theoretically and practically, from all points of view, the connection between 

 this Phlebotomus and verruga could not be more perfect than it is, save for the 

 actual demonstration of the transmission. It is practically certain that the 

 Ceratopogon and other Chironomids cannot carry the infection. While there is 

 yet time for the acarid transmission experiments to show results, and they will 

 be carried straight through, it now appears certain that Phlebotomus is indicated 

 above all others as the agency concerned in the transmission of verruga. 



Verruga Laboratory, Chosica, Peru. 

 29th June, 1913. 



