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



Ephemerella deficiens, sp. nov. 

 Occurrence, habitat. Of similar habitat and closely asso- 

 ciated with Ephemerella serrata in rapid waters, this species 

 is the more common of the two and was collected frequently 

 during the first half of May. It closely resembles E. serrata 

 in shape and size, but the whole body is blackish while the gill 

 lamellae, the legs, and the setae are nearly white. 



Measurements. 



Length of body Length of setae 



Male imago 5 m. m. Setae lost 



Nymph 5.2 m. m. 2.5 m. m. 



Male imago. General color blackish, thorax blackish brown. Head, 

 eyes prominent, upper division reddish brown, lower division blackish 

 brown (living specimen); ocelli white; antennae, carina and rings 

 of ocelli brown. Thorax, above, pronotum brown; the mesothorax 

 and metathorax blackish brown with blackish edges; pleurae brown with 

 edges blackish; sternum brown with a broad transverse band of yellow 

 behind the first pair of legs. Legs nearly white; coxae and an indefinite 

 band at distal end of the femur brown. Wings hyaline shaded with 

 brown at the base. Abdominal segments shaded with brown giving the 

 effect of annular bands dark on the dorsum, paler beneath. Setae 3, 

 pale at the base. (Only the bases of the setae remained when the 

 specimen was taken from the cage). Forceps and penes are figured in 

 PI. IV, fig. 4. 



Nymph (PI. VI, fig. 4, PI. VII, fig. 4, PI. VIII, fig. 4). Color black- 

 ish brown, femora brown, gills, tibiae and tarsi whitish. Body broadest 

 at the metathorax, the thorax arched, the abdomen slightly depressed 

 and curving upward at the posterior end. Setae held upright or curved 

 over the abdomen. Head, bluntly wedged shaped; ocelli inconspicuous 

 whitish; antennae pale with a band of brown just above the basal seg- 

 ment. The maxillae with their palpi totally absent (PI. VIII, fig. 4). 

 Thorax, above blackish brown, the pro thorax bordered laterally by a 

 pale longitudinal band with a brown spot at its center; the prothorax 

 and mesothorax with a longitudinal stripe of pale yellowish on either 

 side the median line. Legs (PI. VII, fig. 4) with the coxae and femora 

 brown, the under side of the latter with a distinct hook shaped area of 

 whitish. Tibia and tarsi pale whitish, the first two pairs of tibiae with 

 a broad middle and a narrow proximal band of brown; the tarsi of all 

 the legs with a middle band of brown and with the claws similar (PI. 

 VII, fig. 4). Abdomen above dark blackish brown. The posterior 

 lateral angles of segments 9-10 pale whitish; the lateral margins of seg- 

 ments 1-9 spinose serrate with their posterior lateral angles produced 

 into flat spines which become more acuminate posteriorly; segment 10 

 without spines and with its posterior margin truncated. Gills present 

 on segments 3-7; Elytroid cover absent; gill lamellae whitish shaded 

 with brown at the base, superior lamina entire, the inferior one bifed. 



