Entomology of the Illinois River. 



171 



Since the number of branches is proportionally 

 nearly as above in all individuals examined, it will be 

 sufficient in the following comparison of larvae of differ- 

 ent ages, to state the formula for the first four abdom- 

 inal segments, addiug also Miiller's figures for P. stratio- 

 tata, a European species. 



The head of the larva is pale, faintly mottled, Y-mark 

 light yellowish brown, setae long, surrounded by light 

 brown ring at base. Clypeus margined in front with 

 dark brown or blackish; labrum deeply but obtusely 

 emarginate; mandibles toothed, tips blackish; palpal 

 joints darker at apex; mentum transversely corrugated ; 

 basal antennal joint truncate-conic, variable in appear- 

 ance, second joint slender, about four times os long as 

 thick, with an apical seta of about equal length, and 

 minute terminal articles; ocelli five, with black angular 

 pigment spots, four in a vertical row, lower three spots 

 contiguous, the fifth lying behind the upper one of the 

 four. 



* Short. + About to moult. 



