EEV. A. E, EATON OX EECENT EPHEMEEID.E OE MAYELIES. 323 



Nortli-Ainerican species differ generically from the European and Asiatic species hereto- 

 fore described, pp. 268-27 ±. 



Tlie descrii^tions which here follow take cognizance only of the adult and subimago 

 conditions. It may, however, hereafter be found that when the nymph-stage of the 

 American form is fully worked out, the opinions here offered tentatively may require 

 modification. 



The following characters of the American species of Heptagenia should be taken into 

 consideration Avith the characters of the genus already given at p. 265. 



P. 265. Adult. — Eirst joint of the hind tarsus equal or subequal to the third joint; 

 first joint of the 6 fore tarsus about half as long as the second, and this rather shorter 

 than the third joint ; first joint of the ? fore tarsus little more than half as long as the 

 second, which is very little shorter than the third joint. Penis-lobes slightly flattened ; 

 their extremities roundly truncate. — Eore leg of d about 1^ as long as the body ; the tarsal 

 joints, in the order of their shortening, rank in the c? , 3, 2, 4, 1, 5, and the first is about 

 ^ as long as the second joint ; and in the ? 3, 2 equal to 5, 1 equal to 4, and the first 

 is -—^ as long as the second, or \ as long as the third joint. The joints of the hind tarsus 

 in the order of their shortening rank in c? 2 equal to 3 equal to 5, 1, 4 ; in $ 5, 2 equal 

 to 3, 1, 4, or 1 equal to 4. Ventral lobe of ? segment 9 emarginate. Outer caudal setse 

 of 6 3-3^ the length of the body ; those of $ I5-2 its length. 



Supplementary to Heptagenia interpuiictata, see p. 267- 



XBaetis canadensis, var. (?), ! Walk., List of Neuropt. lus. in Brit. ]\Ius. part iii. 570 (1853) [?]. 



Subimago {dried). — Wings extremely light yellowish ochre, with neuration at first 

 nearly concolorous with the membrane, and with the extreme edge of the hind wing at 

 the apex and terminal margin blackish grey. The Aviug-neuratiou undergoes changes 

 of colour during the maturation of the insect similar in their nature to those described 

 under Heptagenia sulphurea, the greater part of it, in specimens very near the last moult, 

 becoming bistre- or raw-umber brown, and only the stronger uervures remaining 

 yellowish in opaque view. In the fore wing the cross-veinlets of the foremost three areas 

 (but not the great cross-vein) are black : the dark pigment in many of the specimens 

 spreads a little, anteriorly, on each side of nearly every cross-veinlet in the marginal 

 area ; and in the third of those areas, minute, more or less circular, dark-grey median 

 single spots are similarly apt to be formed upon some or all of the cross-veinlets in the 

 basal half of the area, and where the cross-veinlets are close together near the bulla of 

 the radius two or three of the spots often run together into a dark dash traversing the 

 middle of the cross-veinlets : some of the specimens have none of these spots. In the 

 remainder of the fore wing the cross-veinlets gradually become dark. Seta^ uniformly 

 light brownish. 



Imago {dried), s . — Notum light yellowish approaching yellow-oclu-e, excepting the 

 pronotum, which in some lights approaches pale raw-umber brown ; the sides of the 

 thorax are varied vri.i\\ a much paler yellow. Abdomen in segments 1-8 semitrans- 

 parent greenish white, witli the terminal borders of the segments edged evenly and nar- 



