236 



than the ventral and thickened apically. Thorax and abdomen dense- 

 ly covered with closely appressed silky pile; dorsum of thoracic and 

 abdominal segments each with a transverse series of short, closely 

 placed, backwardly directed spines at suture, the abdominal segments 

 with 3 additional transverse series which do not traverse the whole 

 dorsum and are usually interrupted in one or two of the series ; ven- 

 tral segments each with 2 transverse series of similar locomotor spines 

 on all but the apical 4, these latter bearing a series at the sutures and 

 a transverse mouth-like incision with slightly protruded membranous 

 integument which is densely clothed with short upright hairs (PI. 

 XXXV, Fig. 14) ; hairs in front of the transverse incision on apical 

 segment very long; locomotor spines barely distinguishable except 

 when the larva is alive and in motion ; apical segment terminating in 

 4 rather long stout processes, on the inner under surface of the upper 

 pair of which are the black, round, posterior spiracles, and on the 

 lower pair a long apical hair (PI. XXXV, Fig. 13). 



The larva just described is one that I took from a much-decayed 

 log at White Heath April 30, 191 6. 



It conforms to the general characteristics of the larvae of this 

 family, but I have no means of determining its specific identity as the 

 only specimen I obtained died before pupation. 



The head and thoracic segments were dissected and mounted in 

 Canada balsam ; the remainder preserved in alcohol. 



The structure of the head points to the likelihood of the species 

 belonging to Eriopterinae. 



Genus incertus 2 



Larva (PI. XXXIV, Fig. 8).— Length, 5-7 mm. Yellowish white, 

 with the head and locomotor areas showing blackish. 



Head as in Figures 1, and 4, Plate XXXV, the general shape re- 

 sembling that of Limnobia ; mandibles stout, with apical and lower 

 marginal teeth; labial plate of the same form as in Limnobia. Body 

 slender, the segmentation distinct; locomotor organs consisting of 

 transverse, elevated, slightly leathery areas which are not armed with 

 spinules, their number and arrangement as in Figure 8, Plate XXXIV. 

 Apical segment terminating in 2 long tapering processes which are 

 armed with a number of long hairs, as in Figure 15, Plate XXXIV. 

 Spiracles situated on dorsum at base of terminal processes, their open- 

 ings not conspicuous nor chitinized. 



Described from 4 specimens obtained by Dr. S. A. Forbes from 

 Firehole River below Nez Perce Rock Rapids, Yellowstone National 

 Park, August 16, 1890. 



