230 Illinois State Laboratory of Natural History. 



long as their diameter near base. Lateral spines almost 

 wanting; ventral fringe in front of anal tubercle in male; 

 a tuft of about five spines on each side in place of thi& 

 fringe in the female. 



C. striatus O.-S. 

 Illinois {Le Baron*). 



C. obsoletus Wied. 



One example from Urbana, Aug. 3 ; two from the Mis- 

 sissippi bottoms in Union county, Aug. 11. 



Tabanus. 



On account of the general similarity of habit and struc- 

 ture among tabanid larvae and pupae, the discussion un- 

 der the family heading covers all points to be mentioned 

 regarding this genus. There are many species, and the 

 separation of their immature forms will be at best very 

 difficult. Those known to me represent two quite dis- 

 tinct groups. The species preceding T. lineola perhaps 

 compose a third group, their immature stages being 

 unknown to me. 



The larvae differ from those of Chrysops In the greater 

 variety of striation. That of the upper mesothoracic 

 lateral area is more noticeably coarse than that in the 

 other lateral areas; in the dorsal and ventral areas it is 

 usually wanting or sparser on the disk, at least on the 

 dorsum of the thorax, and more or less restricted to the 

 margin of each area, except in young larvae, in which the 

 striae may all be entire, as they are in Chrysops. The 

 dark ring encircling the membrane at the base of the 

 respiratory tube is not wide and is usually parallel-sided, 

 not reaching forwards to the anal prominence, as in 

 Chrysops, but often joined to it by a lateral isthmus. 



KEYS TO SPECIES OF TABANUS. 



LarvoB. 

 I^ateral shining striated area of prothorax nearly or 

 quite as long as dorsal area; lateral striation not 



* Osten-Sacken, "Prodrome." 



