38 NEW YORK STATE MUSEUM 



cultrifonn galeae, fringed with spinules externally, and broadly 

 triangular laciniae, sejjarate to the base. 



Prothorax rather short, closely aj-iplied to the front of the large 

 mesothorax; wing cases reaching the apex of the second abdominal 

 segment. Leigs rather short, stout, pale, with darker Hues upon 

 the sutures, the darkest one at the base of the claw. 



Abdomen gradually tapering, gracefully upcurving in the rear. 

 Gill laminae on segments 1-7, similar in fonn on all the seg- 

 ments (fig.Cc) ; smallest on segment 1, largest on segment G, obo- 

 vate, with a somewhat thickened front margin, and a longitudinal 

 dorsal chitinous ridge. There are no free gill filaments attached to 

 lamellae. Lateral spines on segments 4-9 straight, sharj), increas- 

 ing in size posteriorly. Setae rather short and stout, equal, 

 fringed co])iously within, traversed by a broad distinct l)and of 

 brown which occuj)ies their middle third, and slightly washed 

 with brown again at the extreme tips. 



This nymph differs from the one figured by Eaton (pl.49. 

 Monograph) in having the middle lobe of the tongue (hypop- 

 harynx) bilobed. This genus differs from all others as yet 

 known except T h ii a u 1 u s in the possession of a pectinated 

 fringe on the distal border of the galea of the maxilla. 



Choroterpes basalis lianks 



This si^ecies I have studied in the Fall creek gorge beside the 

 Cornell Insectary at Ithaca. It is a very common species there. 

 The nymph is found among the smaller stones in the side cur- 

 rents of the creek in the bottom of the gorge, associated with 

 other nymphs of i: c d y u r u s m a c u 1 i p e n n i s , Baetis, 

 Caen is etc. It clambers about under these stones, and when 

 they are lifted out of the water it is easily picked off by hand. 

 The form of the gill tips (Plate S, fig.8) will instantly distinguish 

 it from all others in the stream. 



Imagos were abundant about the middle of July. My bred 

 specimens are dated July 14. 1!)01. Not many imagos were ob- 

 served at large except on early afternoons, when the sunshine 

 was warm and bright. Then they would swanu out in the oi)eu- 

 ing of the gorge, and dance high up in the air between the banks 

 of green in myriads. Kising and falling in rapid undulations, 

 moving in large companies up and down the g(uge, they rarely 

 descended low enougli to bring the lowermost within the reach 



