Localities in which Pellagra is Prevalent. 17 



Pitpa.— Pupa cases were taken from the same rapids as 

 the larvae above described. They were of the "wall-pocket" 

 type and were attached to a bit of submerged bark in one 

 case, to rocks in others. They are elongate, leathery, pale 

 brown, rounded from side to side, becoming gradually wider 

 to the open end, from which projects the head of the brown 

 pupa bearing two tufts of respiratory filaments, each tuft 

 made up of six simple filaments. Length of case 4 mm. 

 (0.056 inch). The case is closed beneath along the attached 

 side for about one-half its length. 



Only the rounded anterior extremity of the pupa shows 

 in the case. The brown tapering filaments project some 

 distance beyond the opening, and together with the case 

 serve to distinguish members of the genus from any other 

 aquatic Diptera. The six simple respiratory filaments are 

 characteristic of but two species likely to occur here, namely, 

 S. venustum, the black fly, and S. meridionale, the turkey 

 gnat. The black fly larva differs, however, in having an 

 independent pair of setae near the tip of the mandible, on 

 the convex side, and the three large teeth of its labium are 

 about equal in size, characters in which the Kentucky speci- 

 mens agree. No adult insects were collected, though I 

 examined the creek carefully on several different days, 

 between Pineville and Gary. One of the pup^ was in 

 process of giving up the adult, as shown in Figure 2, A, 

 a fact proving the emergence of a fall brood, as do a number 

 of empty cases secured. 



Simulium pecuarum (The Buffalo Gnat'"') . 

 In the southern states this gnat is the best known mem- 

 ber of the genus. It has been at times a great pest to stock 

 on the bottoms of the Mississippi and other streams in the 

 South. In former years it was well known in Western Ken- 

 tucky along both the Mississippi and the Ohio rivers. It is 



♦The impression has been conveyed tliat the writer of this bulletin regards tlie Biitfalo 

 Gnat as the species concerned in conveying the virus of pellagra. I have never regarded 

 it as an agent of infection. .All my inciuirles of people residing in the region in which 

 pellagra is most prevalent failed to produce any evidence that this particular species 

 occurs there. Residents knew nothing about it, yet every man, woman and child seemed 

 to know about the ''new disease". On the bottoms of the Mississippi River near Colum- 

 bus, on the other hand, residents are familiar with the Buffalo Gnat, but know nothing of 

 pellagra. 



