Entomology of the Illinois River. 225 



rax is striated above in Chrysops, and smooth or nearly 

 so in Tabanus. The three types of coloration observed 

 are well shown by the three Tabanus larvae figured. 



PupcB. 



The little Chrysops pupae have longer antennae, and 

 the thoracic spiracular prominence is more nearly in a 

 vertical plane than in Tabanus, its inner edge being 

 more strongly elevated. Its lower free edge is crossed by 

 sharp folds, making it serrated. In Chrysops, the abdom- 

 inal spiracles are subeylindrical near the apex; the spi- 

 nose fringes consist of long teeth only; and the terminal 

 teeth are long and rather narrow at the base. 



The great difference between the abdominal spiracles 

 and terminal teeth of the lineola group [Fig. 44, 46] and 

 those of the atratus group [Fig. 52, 54] is evident from 

 the figures. In both, the thoracic spiracles are in a plane 

 nearly parallel to the adjacent surface and the spinose 

 fringes contain long and short spines. The preanal 

 fringe in the lineola group shows more or lesss of a chi- 

 tinous web uniting the bases of the spines. 



A pair of short appressed palpal sheaths on the lower 

 surface of the head, resembling the antennal sheaths, 

 differ slightly' in position in related species of the atratus 

 group. 



Pangonia is unknown to me in the immature stages; 

 it would probably group here with Chrysops. 



KEYS TO GENERA OF TABANID.a. 



Eggs. 



In one flat tier, forming an oval or diamond-shaped area, 

 pointed at one or both ends. [Fig. 42.] Chrysops. 



In an elevated, thick, subconical mass of several tiers, 



[Fig. 55.] Tabarms. 



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