Entomology of the Illinois River. 



251 



Larva [Fig. 57].— Length 30-40 mm., greatest width 

 (6th segment) 5.6 mm.; tenth segment '25.3 mm. wide, 

 last, near base, 1.5 mm., apical half 1 mm.; length of 

 last, segment from preanal fold about 6.5-7.5 mm., or 

 about four times length of anal slit, shorter than this in 

 the young larva. 



Elongate-lanceolate, depressed, rapidly narrowed in 

 iront, acuminately narrowed behind; dark fuscous to 

 blackish, clean specimens showing a cinereous bloom 

 •when dry, lateral edge and six narrow dorsal vittae 

 more or less distinctly pale cinereous; a dark dot sur- 

 rounding the spiracles; on the overlapping margins of 

 the segments the vittae are much lighter and in strong 

 contrast with the intervening spaces, which are here 

 nearW black. The middle pair of light vittae are more 

 distinct than the others, and the dark median dorsal 

 Mne is usually well marked. The other lines are nearly 

 or quite obliterated on the disks of the segments. The 

 <lark groun(3 color above and below is more or less mot- 

 tled with the lighter color— a dot at the base of each 

 hair. Previous to the later moults the larvae become 

 nearly unicolorous blackish. Above and below, in each 

 transverse suture, usuallj' concealed by the overlapping 

 of the segments, is a double row of enlarged impressed 

 granules, or minute shallow pits, and two short rows of 



