1911] May-Flies of Fall Creek, N. Y. 105 



distant and dark grayish, a whitish area of the head showing between 

 them. Thorax, with the pronotum distinctly lined with brown. Sub- 

 triangtilar areas on mesothorax and metathorax present but less dis- 

 tinct than in the male. Abdomen with tergites shaded with brownish, 

 a distinct transverse band of brown near the posterior border. Sternite 

 7 produced backward in a rounded lobe whose posterior edge touches 

 that of sternite S. Sternite 9 produced backward in a lobe with a shal- 

 low median indentation on its posterior margin. 



Female sub-imago. General color much darker than the male 

 imago. Thorax shaded all over with brown. Sternite 7 produced 

 backward only half the length of sternite 8. The prolongation of ster- 

 nite 9 much less pronounced and its posterior margin barely indented. 



Epeorus humeralis. 



(PI. IX, fig. 1, 2, 7.) The genus Epeorus is represented in 

 Fall Creek by this single species. It is closely allied to Iron 

 but differs from it in the greater distance between the lamellae 

 of the first and last pairs of gills. These nymphs are much 

 larger than those of Iron fragilis, but are harder to transport 

 because of the extreme brittleness of the bases of the lamellae. 



Occurrence, habitat. Full grown nymphs and imagoes were 

 taken at various dates from May 25 to July 15. This species 

 is very common in the swift waters associated with Heptagenia 

 and Baetis. 



Epeorus humeralis sp. nov. 



Measurements. 



Length of body Length of setae Antennae 



Male imago 10 m. m. 20.5 m. m. 



Male subimago 9 " L2.5 



Female imago 9.5 ' 13 



Female subimago 10 " 11.5 



Nymph 11 " 11 " 2.5 m. m. 



Male imago. (PI. IX, fig. 2, 7). (Live specimen). General color 

 dull yellowish, becoming sub-hyaline on segments 2-5 of the abdomen. 

 Conspicuous dark brown spots at middle of femora in all winged stages, 

 larger than those in Iron fragilis; the body less fragile than that of the 

 preceding species; the humeral cross vein blackish; the foreleg about 

 three quarters the length of the body. Head, yellowish white; eyes 

 conspicuous olive green, ■ intersected in the lower portion by a brown 

 band, ventral edge margined by a narrow black band border behind, 

 this in turn by a white band of the same proportions; antennae brown, 

 a brown ridge extending from their basal segments to the inner margins 

 of the eyes; carina on middle of front brown; ocelli ringed with olive. 

 Thorax, above yellowish white, translucent; pronotum partially hidden 

 by the eyes, its lateral lobes shaded with dark brown; mesonotum 

 buffy with edges brown and elevations lighter; scutellum fuscous. 



