Entomology of the Illinois River. 193 



smooth lines three lougitudiual rows, with two interven- 

 ing rows less plainly indicated ; behind the middle of 

 each segment the middle row rises, and in the greater 

 space between it and the lower row, the intervening row 

 becomes fully developed. The first four abdominals 

 gradually increase in length, the first one being about 

 as long as the thorax; the first three bear near their 

 posterior margin beneath, a pair of prominent false feet 

 {Fig 17], each with a sharp slender claw or hook at 

 apex; the fourth and fifth are about equal in length; 

 the sixth is about two thirds as long and conically 

 narrowed towards apex; the seventh is much narrower 

 and shorter, scarcely half as long as the fifth, at base 

 about half the diameter of the main body, and narrowed 

 to apex, reddish brown, granulate and sparsely pilose, 

 the setiferous tubercles almost wanting; the remaining 

 two segments form a long and very slender partly re- 

 tractile respiratory tube with the stigmatal opening at 

 the tip, dirty whitish, smooth, and semi-transparent, 

 the eighth segment short, about as long as the seventh, 

 the ninth extremely long and attenuated, as long when 

 extended as the distance between its base and the third 

 pair of false feet, bearing at its anterior third, beneath, 

 a pair of slender tracheated filaments about one half the 

 length of the basal part of the segment. 



Papa [Fig. 18-22].— Length 20-25 mm., exclusive of 

 the long respiratory tube, which measures about 35 

 i!im.; diameter of abdomen 2.5 to 3 mm. Cyhndrical, 

 thorax shghtly thicker; abdomen dirty whitish, with 

 numerous spots and transverse bars of brownish fus- 

 cous, which bear minute cylindrical setiferous projections; 

 thorax light to dark fuscous brown. 



Head quadrituberculate in front. Respiratory tubes 

 arising close to anterior margin of prothorax, unequal, 

 one of them greatly elongated and bristle-like, about .2 

 mm. in diameter, slightly' tapering, finely annulated, 

 ending in an oblong yellowish brown knob, with a flat- 

 —13 



