226 Illinois State Laboratory of Natural History. 



LarvcB. 



Last antennal joint much longer than the one preceding,, 

 dorsal areas of thorax striated like those of ab- 

 domen Chrysops. 



Last antennal joint not longer, usually much shorter^ 

 than the one preceding; dorsal areas smooth or 

 striated, but those of thorax nearly or quite free^ 

 from striae Tahanus. 



PupcB. 



Antennae surpassing adjacent margin of head ; fringes 

 of abdomen of long spines only; inner margin of 

 thoracic spiracular prominences sharply elevated, 

 lower margin serrate-edged; abdominal spiracles 

 slender, subcj'lindrical near apex; size 8ma\\..Ch7ysoj}s. 



Antennae not attaining margin of head; fringes of ab- 

 domen of long and short spines; inner edge of thoracic 

 spiracular prominence not, or but slightly, more prom- 

 inent than outer edge; abdominal spiracles subconical 

 or rounded; size medium or large. [Fig. 4:3.']..Tahamts. 



Pangonia. 

 J*, rasa Loew. 

 Illinois {Ze Baron*). 



Chrysops. 

 O. excitans Walk. 



One example, margin of Grass Lake, Lake Co., June 

 22. 



G. mitis O.-S. 



A specimen with all the characters of this species, but 

 nearer C. fugax in size, was taken June 15 near Sand 

 Lake, Lake county. Dr. Williston also mentionsthe small- 

 er size of a specimen in his collection (Trans. Kans. Acad. 

 Sci. Vol. X., p. 132). 



♦ Osten-Sacken, "Prodrome of a Monograph of the Tabanida; of the United States," 

 Part I., p. 366. 



