233 



— Lower process on each side of apical abdominal segment with only 



the fringe of short hairs, no long terminal hair being present. . ,2 



2. Labrum with a leaf-like lobe on each antero-lateral angle which is 



directed anteriorly and mcsad, the pair almost meeting so as to 



shield the anterior margin of the labrum Hexatonia. 



— Labrum either rounded or but slightly produced at the antero-later- 



al angles, lobes, if present, not directed mesad, and the apices 

 of the pair widely separated Eriocera. 



PUPAE 



1. Apices of fore tarsi ending much proximad of apices of mid and 



hind pairs Hexatotna. 



— Apices of fore tarsi ending on a transverse line with mid pair, the 



hind pair sometimes extending distad of the latter 2 



2. Thoracic respiratory organs very noticeably swollen at bases and ap- 



ices, the constricted central portion with transverse wrinkles .... 

 PentJioptera. 



— Thoracic respiratory organs of nearly uniform thickness throughout 



their length, sometimes tapering from near base to apex 



Eriocera. 



I have before me a number of larvae of this subfamily, but can as- 

 sociate none of them with a described species as neither pupa nor imago 

 are in the collection. Our specimens, with but one exception, were 

 obtained by Dr. S. A. Forbes in rivers in Yellowstone National Park ; 

 the single one was taken by Dr. C. C. Adams in Montana. The species 

 in their larval stage appear to be confined to swift-flowing streams. 

 No examples have been obtained in Illinois though much careful work 

 has been done on the Illinois River. It is not improbable that an ex- 

 amination of some of the smaller swift-flowing streams in the more 

 hilly sections of the state will discover the presence of these larvae. 

 They are usually found under stones when in the current, but come 

 ashore to pupate in the sand or mud of the banks. 



The species almost invariably have the appearance of Figure 14, 

 Plate XXXIV, when preserved, the integument of the penultimate 

 segment distending remarkably in some specimens. Brauer, in his 

 paper previously referred to, has figured a species with this charac- 

 teristic distension. The Hng membranous appendages of the maxillae 

 probably serve the purpose of guiding the food into the mouth, being 

 analogous to the mouth-fans of the family Simuliidae — also found in 

 swift-flowing waters. 



