jLntomology of the Illinois Ri/oer. 223 



middle, each divided by a notch into two lobes. Beneath, 

 the head bears on each side a pair of seliferous tubercles, 

 and between these a pair of short closely appressed 

 palpal sheaths. The three small tubercles supposed 

 to represent the ocellar triangle lie at the point of 

 separation of the head and the two halves of the tliorax, 

 one on each, and are indistinct in smaller pupse. The 

 upper margin of the head is angulate at middle and over 

 each antenna. 



Thorax obsoletely wrinkled ; pro- and mesothorax sep- 

 arating and splitting on the well-marked middle line 

 above at time of emergence. Prothorax about as long 

 as the anterior surface of the head with a setiferous 

 tubercle each side near the ocellar triangle and another 

 at each hind angle ; an impressed curve originates above 

 each antenna. Mesothorax one half longer than pro- 

 thorax; its anterior margin extended angularly forward 

 on each side, bearing ~at this point a large darker spir- 

 acular prominence [Fig. 45, 53] with an arcuate rima 

 or air slit, closed by a thin membrane; inwardly from 

 •each prominence is a deep closed notch in the margin; 

 disk with two small setae each side; wing-pads attain- 

 ing second abdominal. Metathorax very short at mid- 

 dle, sides a little longer and with two angles in front; a 

 seta each side. 



Abdominal segments about equal in length, the first 

 obsoletely transversely wrinkled, one seta, or more, each 

 side on an obsolete ridge near hind margin. Next six 

 segments distinctly transversely wrinkled, encircled by a 

 continuous fringe of slender spines, borne upon a slight 

 ridge near the hind margin. Lateral areas of first seven 

 segments limited by sharply impressed lines, and slightly 

 elevated, each bearing a rounded spiracular tubercle 

 [Figs. 44, 52]. Last segment short with a truncate tip 

 [Figs. 46, 54] margined by six acute teeth; anal tuber- 

 cle beneath large in tlie male, with a fringe of spines 

 in front of it ; small in the female, the fringe broadly inter- 

 rupted at middle; a few lateral spines on this segment. 



