250 Arthropod Transmission of Disease 



lacious. In Spartanburg County attacks by Simulium seems to be 

 confined to the immediate vicinity of the breeding-places. Our 

 records and observations, exceedingly few in number, refer almost 

 exclusively to such locations. Statements regarding such attacks, 

 secured with much care and discrimination from a large number of 

 persons, including many pellagrins, indicate conclusively that these 

 insects are seldom a pest of man in this county. A certain ntunber 

 of the persons questioned were familiar with the gnats in other 

 localities, but the majority were seemingly ignorant of the existence 

 of such flies with biting habits. This is especially striking, in view 

 of the fact that the average distance of streams from the homes of 

 the pellagra cases studied was about 200 yards, many being at a 

 distance of less than 100 yards, and that 78 per cent of these streams 

 were found to be infested by larval Simulium. Such ignorance in a 

 large number of persons caimot be overlooked and indicates strongly 

 that our belief in the negHgible character of local attacks by Simulium 

 is well founded." 



"In localities infested by 'sand-fiies,' mosquitoes, etc., these 

 pests are always well known and the ignorance described above is 

 very significant." 



"Such positive reports as we received nearly always referred to 

 bites received in the open, along streams, etc., and observations made 

 of their attack were of those on field laborers in similar situations. 

 Males engaged in agricultural pursuits are almost exempt from 

 peUagra in Spartanburg County. During the season of 19 13, in 

 some two or three instances, observations were made of the biting 

 of Simulium and some additional and entirely creditable reports 

 were received. These observations and reports were under condi- 

 tions identical with those referred to in the reports of 191 2 and con- 

 firm the conclusions based on the observations of that year. I 

 would repeat with emphasis that it is inconceivable that a fly of the 

 appearance and habits of the prevalent species of Simulium could be 

 present in such a region, especially about the haunts of man and 

 attack him with sufficient frequency and regularity to satisfactorily 

 account for so active and prevalent a disease as pellagra without 

 being a well-known and recognized pest . ' ' 



"In connection with the conditions in the Piedmont region of 

 South Carolina, it may be well to cite the results of a study of those 

 in the arid region of western Texas." 



