Localities in which Pellagra is Prevalent. 31 



with several long soft hairs. Segmentation distinct. Pos- 

 terior prolegs long, projecting far beyond the posterior 

 somite. Dorsal tufts of setse of posterior somite arising 

 from long pedicels. Two long setae at posterior edge of the 

 som'ite behind the tufts. Respiratory appendages dusky, 

 tapering, about half the length of the prolegs. See Fig. 26. 

 Still other larvse belonging to related genera were ob- 

 served, among them one with swollen anterior body segments 

 and evidently belonging to the genus Tanypus. They are 

 largely fragile, harmless gnats when adult, and the relation 

 they bear to Simulium as competitors or enemies may be the 

 only one they sustain to the immediate subject of this paper. 

 Such larvae often constitute an important element of the food 

 of other aquatic animals. 



No. 5.— A number of singular dipterous larvae were 

 collected near the Roark cottage on Straight Creek, while 

 searching for Simulium larvae and have not been definitely 

 determined. The figures 27 and 28, of larva and pupa, give 

 a good idea of their character. The specimens were all 

 taken together from a piece of submerged wood in rapid 

 water. 



It is a sluggish rather stout, tough-skinned grub, with a 

 small head which widens rapidly from the anterior ex- 

 tremity to the base, giving it a somewhat triangular outline. 

 The sides of most of the body divisions are produced and 

 pointed, each process bearing a long, curved bristle near 

 its tip. Posterior extremity of body expanded into a 

 clawed disc. Ventral sides of first body division (pro- 

 thorax) with two clusters of obliquely-placed, curved, 

 black hooks. Head dusky brown; antenna short, erect. 

 A black speck at the base of each. First body division dusky 

 at sides, widest posteriorly; second, widest of the three 

 thoracic segments; third, a little narrower, with a very short 

 lateral point and bristle; first to seventh somites constituting 

 the abdomen, each with a strong lateral extension and bristle; 

 eighth division narrower, a little angular at middle, but 

 with no process; ninth expanded and provided with strong 

 curved hooks beneath, a pair of long hairs projecting pes- 



