126 CHARLES H. T. TOWNSEND — PROGRESS IN THE STUDY 



mud walls of dwellings in the Peruvian montanya of the Chachapoyas region, 

 but is unknown in the verruga zones. Ornithodoros talaje, G. M., occurs on 

 sea-birds along the Peruvian coast and on the guano islands, but no Argasid tick 

 has been taken on mammals in the verruga zone. Thus the outlook for tick 

 work in connection with verruga transmission has seemed less promising than 

 ever as the investigation progressed, taken in conjunction with the negative 

 results of the acarid infection experiments. A recast of the transmission 

 possibilities has therefore become desirable. 



At this juncture the writer recalled the repeated reports of biting gnats in the 

 verruga zone that have reached him since the inception of the investigation, but 

 which he had laid aside so far as referring either to Simulium spp., or to Chiro- 

 nomids which are prevalent outside the verruga zones. Specimens of biting 

 gnats, reported to be what are known to the natives as titira, secured by 

 Dr. A. L. Barton in November last from the verruga zone, proved to be a 

 common Chironomid, not confined to the verruga belts. At Matucana, the 

 writer was told in January of a biting gnat, but the only specimen that could be 

 procured proved to be a Cecidomyid. In March, Mr. Otto Holstein, Chief of 

 Traffic for the Central Railway, stated that biting gnats had entered his car at 

 night while in San Bartolome and had bitten the inmates, his description indica- 

 ting a gnat more slender than Simulium. It was thought at the time to be a 

 Ccratopogon sp., which occurs also at Chosica outside the verruga zone. In 

 April, gnats caught by a native in the writer's presence at the mouth of 

 Verrugas canyon and stated to have been biting, proved to be Borborids. Thus 

 being so far unable to obtain any bona-fide biting gnats in the verruga zones 

 other than Simulium and certain common Chironomids that exist elsewhere, and 

 never having passed a night within the permanent limits of the zones, the writer 

 had never been able to gain authentic information of any gnats therein that 

 might be suspected of being confined to these zones. While all bloodsuckers, 

 wherever met, both in and out of the verruga zones, were carefully collected 

 and studied, Culicids, certain species of Ceratopogon and other Chironomids, 

 Simulium, Tabanids, fleas, bugs, Stomoxys, lice and other hexapod bloodsuckers 

 known in the region were confidently excluded from the possibilities of verruga 

 transmission on account of their habits and occurrence outside as well as inside 

 the verruga zones. 



Mainly with the possible occurrence of Phlebotomus in mind, these reports 

 were now followed up as a promising clue, not only because of the persistence 

 with which they had presented themselves, but also because of the writer's 

 experiences with Oecacta and similiar forms in Mexico, and because of a re- 

 minder recently in a letter from Dr. Adolpho Lutz that Ceratopogoninae 

 and Phlebotominae may bite in early evening and enter houses, though not 

 natural frequenters of dwellings. Above all, the recently published results of 

 Marett and Newstead on the Phlebotomus flies of the Maltese Islands, in which 

 the early-stage habits and habits of the flies themselves are detailed, indicated 

 that Phlebotomus is almost certainly the verruga transmitter, provided it occurs in 

 the region affected, as it well might do. 



Accordingly the writer spent the night of 25th June 1913 at San Bartolom< ; , 

 a noted endemic focus of verruga in the Rimac valley, just below Verrugas 



