104 EEV, A. E. EATON ON EECENT EPHEMEEIDvE OR MAYFLIES. 



whole-figure of the nymph is fairly characteristic of a Blasturus; but tliat of the 

 detached gill (fig. 13) differs from the typical tracheal branchiae of this genus in having 

 the slender tail-points of the laminae in complete continuity with rest of the membrane. 

 It is needless to detail references to Geoffroy, Fabricius, Berkenhout, Gm^lin, Eossi, 

 Schranck, Cederhjelm, Walckenaer, Latreille, and Stewart, who quote Linne's diagnosis. 

 In 1871 I ranked E. vespertina with the typical species of Leptophlehia, citing as 

 synonyms Ephemera albqyennis, Eetz. no. 181 (1783), and Baetis fusca, Burm., Handb. 

 der Ent. Bd. ii. Abth. ii. 800 (1839). It was cited as a Cloe by Oulianine in 1867. 



CHOROTERPES, Etn. 1881. 



niusirations. Adult (details), PI. XII. 19; (whole figures) see Pictet, Potamanthus 

 X marginatus, op. c'd. pi. 25 (1843-5). Nymph, PL XXXIV. 



Adult. — Hind wing in front strongly and somewhat obtusely angulated nearly midway 

 between the tip and the wing-roots, the angle, roughly speaking, forming the vertex of 

 an obtuse triangle whose base is the radius (3) ; the exterior side of the triangle is not 

 straight, presenting a shallow sinus about the extremity of the subcosta (2), followed by 

 a very slight salient curve ; its other side is somewhat rounded off at the wing-roots ; 

 the very gently curved subcosta lies rather nearer to the costa than to the radius, and 

 terminates obliquely in the margin a little beyond the salient angle, in the vicinage of 

 which the narrow marginal area is slightly dilated ; the submarginal area is subtriangular, 

 with the vertex obtuse ; several cross veinlets occupy the distal ^ of the former area, and a 

 larger number the adjoining f of the latter area. Cross veinlets plentiful towards the 

 apex of the fore wing, but sparse elsewhere ; next to none present in the marginal area 

 before the bulla; in the hind wing they are faudy numerous. The nervures of both 

 wings are devoid of branchlets at the terminal region, and there are no isolated veinlets 

 there. The axillar nervures (9' and 9-) of the fore wing, strongly arched and mutually 

 subparallel in the specimen figured, are often disposed in a manner similar to those of 

 the wing represented in PI. XIII. 20 * -. The anal-axillar interspace of the fore wing 

 contains four intercalary nervures, of which 1 and 3 are long, 2 and 4 short ; they are 

 commonly abrupt and linked together by few cross veinlets ; very frequently intercalar 1 

 is connected with the anal by several cross veinlets, and occasionally intercalar 3 esta- 

 blishes direct communication with the first axillar ; intercalars 2 and 4 sometimes remain 

 isolated from the others. The guard is lacking at the orifice of the mesothoracic spiracle. 

 Porceps-limbs of 6 4-jointed ; joints 1, 3, and 4 short, the 2nd joint long, somewhat 

 incurved, moderately compressed, and rather broadly dilated beneath at the base ; forceps- 

 basis short and stout, slightly emarginate in the middle ; the corresponding ventral lobe 

 of ? obtusely rounded and entire at its extremity. Median caudal seta subequal to the 

 others ; outer setse of 6 about 11^ as long as the body. Tarsal ungues dissimilar each 

 to the other. Pore tarsus of 6 nearly as long as the tibia, which is about If as long 

 as the femur ; the joints in diminishing sequence rank 2, 3, 4, 5, and 1 ; hind tarsus 

 (exclusive of joint 1) nearly \ as long as the tibia and joint 1 combined; its joints rank 

 5, 1-3 (subequal), and 4 ; joint 1 is fairly defined. 



