224 Illinois State Lahoratoi^ of Natural History. 



CHARACTERS USED IN TABULATING GENEKA OF TABANID^E, 



Larv(B. 



The larvae aud pupae of Chrysops, as well as the imago^ 

 are distinguishable from those of Tabanus by the anten- 

 nal structure, as stated in the keys. Otherwise the 

 Chrysops larvae closely resemble in structure snmll or 

 young Tabanus larvae. The dull pubescent annuli are 

 partly present in Chrysops, but the longitudinal lat- 

 eral lines, except on the prothorax, are shining and al- 

 most entirely without pubescence. There is very little 

 pubescence here, however, in some young Tabanus larvae. 

 The species herein described [Fig. 41] is easily recog- 

 nized by the dark patch on the last segment. 



The Tabanus larvae and pupse studied form two groups, 

 which may be called the lineola and the atratus groups. 

 The larvae show the most distinctive characters in the 

 sculpture of the surface, especially that of the prothorax» 

 which has lateral, dorsal, and ventral shining areas^ 

 limited in front by an opaque pubescent annulus. Com- 

 paring the anterior extension of these shining areas, we 

 find them all of about the same length in Chrysops and 

 the lineola group of Tabanus, although this length 

 varies in the Chrysops. The lateral prothoracic areas are 

 extensively invaded by the anterior annulus in the atratus 

 group of larvae, the striated shining space becoming ba- 

 sal, being not more than half as long as the dorsal area. 

 The upper lateral space of th(^ mesothorax is not very 

 closely striate, and quite shining. In all except some of 

 the atratus group the remaining lateral striation, in- 

 cluding that of the prothorax, is not much finer, and 

 is also shining, but in the others (as in atrattis) the pro- 

 thoracic and abdominal lateral striation becomes micro- 

 scopically fine and even subopaque. A smooth spot 

 near the lower hind angle of the prothoracic lateral area 

 also gives good characters. The dorsal and ventral 

 striation varies in extent according to age, but the tho- 



