52 EEV. A. E. EATON ON EECENT EPHEMEEIDiE OE MAYFLIES. 



or light yellowish ochraceous; changing in transmitted light to light yellowish amber; 

 the ungues, the terminal joint and the distal borders of the other joints of the tarsus, warm 

 sepia, burnt-umber brown, or pitch-black, the dark colouring in the intermediate joints 

 of the tarsus sometimes predominating almost to the exclusion of the light ground- 

 colouring, at other times narrowly restricted to their terminal borders. Wing-membrane 

 usually quite clear in the disk, bistre- or raw-umber brown in the marginal and submar- 

 ginal areas of the fore wing, and narrowly grey or intense sepia along the terminal margin 

 of the hind wing ; but sometimes even those areas in the fore wing from the wing-roots to 

 the pterostigmatic space are colourless, and the bordering of the terminal margin of the 

 hind wing is either limited to a faint spot at the apex of the wing or is entirely deficient. 

 The cross veinlets, which are liable to be bordered with black or grey in the subimago, 

 are apt to exhibit corresponding greyish markings in the imago. Individual specimens 

 occasionally have the greater portion of the wing-membrane tinted almost imperceptibly 

 with greyish. Neuration of similar colour to that of the subimago. 



The ? has the thorax nearly of the same colours as the d ; the abdomen very light 

 brownish ochraceous or burnt-umber grey, or vandyke-brown, marked with burnt-umber 

 brown in the opaque portion, but with bistre in the empty terminal segments ; the median 

 dorsal stripe corresponds in variety of form with that of the d , the latero-dorsal stripes 

 are of the broad serrated type, the ventral markings vary as in the d . Fore legs usually 

 piceous, either entirely, or with the tarsal joints whitish at their bases ; one example has 

 the fore leg bistre-brown, with the terminal tarsal joint and the extreme edges of the 

 others black. Hinder legs, in opaque view, light bistre-brown, sometimes with the tibia 

 and tarsus darker than the femur ; the terminal joint of the tarsus and sometimes the 

 terminal borders of the other joints intense burnt-umber or piceous. Setae light warm 

 sepia-brown with opaque joinings, or sepia-grey with dark sepia joinings. Wings with 

 transparent membrane and pitch-black or pitch-brown neuration, the longitudinal ner- 

 vures becoming lighter close to the wing-roots ; hind-wings commonly, but not invariably, 

 bordered narrowly with dark sepia along the terminal margin and at the adjacent angles, 

 the bordering uneven in its definition along its inner edge ; fore wings often almost 

 imperceptibly and narrowly tinted with very light sepia-grey along the corresponding 

 margin, and more distinctly tinted with sepia-grey in the pterostigmatic region ; in many 

 examples the marginal and submarginal areas of the fore-wing, anterior to the bulla, are 

 more lightly tinted with the same colour. Cross veinlets in the fore wing between the 

 costa and the pobrachial (7) nervures, and those in the hind wing from the subcosta to 

 the first axillary nervure (9), generally (but not in every specimen) bordered with light 

 or dark sepia-grey ; this bordering is usually lighter in colour and narrower in the fore 

 wing than in the hind wing, and frequently forms irregular blots upon the stem of the 

 sector (4), the end of the longest adventitious nervure contained within its fork, and upon 

 the end of the corresponding nervure included within the fork of the praebrachial (6). 

 Length of body, d 2 lG-23 ; wing, d 14-21, ? 18-22 ; setse, d 44-65, subim. 21-25, 

 S 35-40 and 1, subim. 17 mm. 



Sab. Generally distributed in North America, in lakes and rivers, from Louisiana 



