Entomology of the Illinois River. 221 



rowing actively in search of food. This probably con- 

 consists largely of soft larvae, and they have also been 

 known to devour water-snails not protected by an 

 operculum. In open water they project themselves for- 

 ward by horizontal strokes of the posterior end of 

 the body, and are often found floating, making 

 efforts at progression, but acting as if out of place. Ac- 

 cording to Garman,* they are eaten in quantities by the 

 channel catfish and occasionally by bull-pout. 



The eggs [Fig. 42, 55] are deposited in summer in 

 masses on rushes and other smooth surfaces over water 

 or wet ground; the larvae hibernate nearly full grown 

 and transform in May and June. 



The pupae [Fig. 43] are also very similar to each other 

 and are formed on shore, concealed in damp rubbish 

 They resemble lepidopterous pupae, but may be known 

 at once by the large somewhat ear-shaped spiracles 

 [Fig. 45, 53] on the back of the thorax. 



COMMON CHARACTERS. 



All the larvae and pupae of Tabanidae studied, agree in 

 the following general characters. 



Z«/■^'flB.— Body cylindrical, 11-jointed, not counting the 

 head, tapering at both ends, which are somewhat pointed; 

 skin shining and glassy, more or less striated, whitish, 

 with opaque markings of a microscopic felted pubescence, 

 variably present in the form of rings upon the sutures 

 and false feet, and lateral stripes accompanying the 

 four punctate lines of each side; areas between these 

 lines longitudinally striated, remaining surface often 

 striated, at least in the young. 



Labrum and epistoma [Fig. 51, c] forming a median 

 "partition anteriorly, upper edge grooved, lower applied 

 to the bifid tip of the mentum [d]; a pair of long claw- 

 like black mandibles [e] each side of it, each with a short 

 eubapical groove; exterior to these the pale maxillae 



♦Hull. 111. State Lab. Xftt. Hisf., Vol. III., p. 156. 



