Localities in which Pellagra is Prevalent. 59 



rocks are overturned. Three different forms of these larvae 

 were collected. By far the commonest is represented by 

 Figure 47. 



Larva No. i.— Elongate, flattish, the head wide, pro- 

 duced into a pronounced angle behind each eye. Next three 

 divisions (thoracic) of body with expanded dorsal plates, 

 the two hindmost a little produced backward at sides. Six 

 tufts of fine gill-filaments are placed about the legs of each 

 side, and another within the base of each long posterior 

 abdominal sylet, making fourteen in all. The back is 

 brightly marked with black and yellow. The longest ex- 

 ample, taken June 15, 1892, from the. Cumberland River, at 

 Pineville, is about three-quarters of an inch long. Other 

 examples collected, from Straight Creek, Clear Creek and 

 Cumberland River, in August and October, 1911, range from 



5 to 20 mm. in length. 



Larva No. ^.— Small, slender, the head and thorax but 

 little wider than the abdomen, the sides of the head behind 

 the eyes rounded and not produced. Abdomen rather long, 

 its sides parallel. No gills. Color plain olive. One example 

 5.5 mm. long, but with the wing pads well developed and 

 thus ready to produce the adult, was taken from Horse 

 Creek at Corbin, August 29, 1911. 



Larva No. 3.—K singular, flat larva was taken from 

 a spring-fed rill near Cary along Straight Creek, October 

 21, 1911. It is represented in my Figure 48. In general 

 shape it resembles a small roach, the head and thorax being 

 excessively expanded, the antennae tapering, and the stout 

 legs with two tarsal claws. The length of this example is 



6 mm., its greatest width 2.5 mm. On looking over some 

 old material collected by me at Pineville in June, 1892, I find 

 a second example of the same insect, measuring 2.5 mm. in 

 length. Head wide, bent downward; eyes at outer angles; 

 antennae long, regularly tapering, many jointed (broken at 

 tips). Dorsal plates of the-three thoracic divisions broadly 

 expanded, overlapping, the posterior lateral angles rounded, 

 the posterior margin broadly and evenly, though slightly 

 concave. Abdominal somites abruptly narrower, contracting 



