228 



I do not include in the following synopsis of characters, nor in my 

 keys, genera which I do not possess, though they may have been de- 

 scribed by other authors; but notes upon Brioptera are given in the 

 text owing to the existence of a previous record of the occurrence 

 of a larva of that genus in Illinois. 



SUBFAMILY CHARACTERS 



Larva. — Slender, cylindrical, tapering slightly towards both ex- 

 tremities, the body covered with dense decumbent pile. Head small, 

 poorly chitinized ; labium unchitinized ; the main portion of head con- 

 sisting of slender chitinized rods, 4 or 6 in number. 



Pupa. — Head as in Limnobiinae, without projections; palpi 

 straight; directed laterad. Thoracic respiratory organs short, or if 

 of considerable length, still noticeably shorter than those of Limnoph- 

 ilinae known to me, and of a uniform strength throughout; legs 

 longer than wings. Abdomen with weak armature, which is not in 

 the form of transverse bands or series of spinules; spiracles distinct. 



Imago. — See key to subfamilies. 



Keys to Genera 



larvae 



1. Body with almost indistinguishable surface hairs; ventral surface 

 of abdominal segments without distinct transverse pseudopod- 

 like swellings Helobia punctipennis. 



— Body covered with rather long and very dense decumbent hairs 



which give the larva a silky appearance ; ventral surface of ab- 

 dominal segments with distinct transverse pseudopod-like swell- 

 ings GnopJiomyia tristissima. 



PUPAE 



1. Thoracic respiratory organs pressed close against surface of thorax ; 

 legs extending very slightly beyond apices of wings (PI. XXVIII, 

 Fig. 15) GnopJiomyia tristissima. 



— Thoracic respiratory organs erect, tube-like, not pressed against sur- 



face of thorax ; legs extending very far beyond apices of wings . . 

 Helobia punctipennis. 



Helobia St. Fargeau 



GENERIC CHARACTERS 



Larva. — Cylindrical, slightly tapering towards the extremities. 

 Head small, entirely retractile, caudad of mandibles consisting of 6 



