Entomology of tJie Illinois River. 187 



Respiratory tube wanting or rather short. 

 A row of ventral suckers and of lateral tracheal 

 gills; body on isci form (sow-bug- shaped) and hard- 

 shelled; living in running wSit&T..Blepharocerid(JB. 

 No such rows of suckers and gills, body elongate, 

 soft. 

 Larva moderately slender, with false feet on 

 some of the anterior abdominals; swim- 

 ming in a U-shape. (Dixa M\(\o;e&.)..DixidcB. 

 No false feet on anterior abdominals. 

 Body without false feet. 

 Bod\^ not very elongate and worm-like; tho- 

 rax thickened, its segments more or less 

 connate; last segment with a longitudinal 

 fan of swimming hairs beneath, and often 

 a short respiratory tube above. (Mosqui- 

 toes.) '. Culicid(2. 



Body very slender and cylindrical. 

 Last segment with two fleshy points. 



(False Crane-flies.) Rhyphidce. 



Last segment tapering, entire, with some- 

 times a circular fringe of hair around 

 posterior tip. 



ChironomidcB {Ceratopogon), 

 Body with false feet. 

 False feet on prothorax and on last seg- 

 ment ; body subcylindrical. (Midges or 



Gnats.) ChironomidcB, 



A single median false foot on prothorax; 

 abdomen much broader posteriorly, foot- 

 less, with a terminal sucking disk ; head 

 with a pair of fan-like organs. (Buffalo 



Gnats or Black Flies.) Simnliid<B. 



Mandibles parallel, their motion vertical or obliquely in- 

 wards. [Fig. 51.] {Brachi/cera.) 

 Posterior stigmata very a.p[)roximate, placed within a 

 terminal stigmatal cleft. 

 Stigmatal cleft vertical, head retractile. [Fig. 50.] 

 (Horse-Hies.) TahanidcB. 



