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



with the anal at the roots, and running nearly alongside of it for some distance, presently 

 recedes from it in a bold curve to the middle of the inner margin. Hind wings well 

 developed, broad ; the costal shoulder sharply defined, almost right-angled, and situated 

 at about the first ^ of the front margin ; the subcosta (2) elbowed correspondingly, and 

 approximated to the costa soon after the flexure. Thoracic spiracles str.iight-lipped, 

 usually closed in dried specimens. Forceps-limbs inserted at the sides of the terminal 

 border of a transverse laminar lobe prolonged from the segment, which lobe is repre- 

 sented in the ? . Eyes of d evenly contoured ; anterior ocellus rather smaller than the 

 others. Subimago quiescent many hours. 



Section 4 of the Genera. — Type of Fotamanthus. Adult. — Proximal joints of 6 

 forceps-limbs many times longer than the remainder combined. Nymph. — Wings free 

 along their terminal margins. Palpus of maxilla I. longer than the lacinia. Lobes of 

 the labium smaller than the lacinise of maxilla3 II. Abdominal segments 2-7 branchiate ; 

 the gills inserted into postero-lateral prominences of the segments, and divergent back- 

 wards from the sides of the body ; hinder lateral angles of tlie segments not prolonged. 

 Natation laboured, aided by movements of the legs ; fore legs of moderate proportions 

 and simple construction, the femur rather shorter than the tibia. 



The insects ranked in this section have strong affinity with the Ephemerce. The chief 

 differences between the flies consist in the structure of the forceps, the laminar lobe 

 of the ? 9th ventral segment, and the bifurcation of the second axillary nervm'e of the 

 fore wing. This last characteristic is met with in some uudescribed allies of Fotunumthus, 

 as well as in all that have been published. The nymph has more congruity with the 

 Leptophlebiae ; and the structure of the flies justifies their being grouped with these 

 rather than with Ephemera. 



POTAMANTHUS, Pict. 1813-5; restricted, Etn. 1871. 



Illustrations. Adult, PL IX. 14 (details) ; (whole figures) Pict., Hist. Nat. Nevropt. 

 ii. Ephdm. pi. xxv. 1-3 (1843-5). Nymph, PI. XXXI. (whole figure and details) ; refer 

 also to Eucharidis, Joly (1876), under P. luteus. 



Adult. — Seta) 3, subequal to each other ; in s im. about \\, 2 Ij, and in s subim. just 

 as long as the body. Pore leg of s as long as the body, the tibia If as long as the femur, 

 and nearly as long as the tarsus ; ? fore femur almost as long as the tibia, tarsus nearly 

 \ as long as the tibia ; hind tarsus about \ ^s lo^a ^s the hind tibia ; ungues unequal, 

 and (excepting in s fore tarsus) dissimilar. Anterior ocellus a little smaller than the 

 others. Pronotum of 2 transverse, produced into a flattened lobe closely appressed to 

 the mesonotum and rounded posteriorly. Lobes of the penis flattened, without apparent 

 stimuli. Body slender : abdominal segments of ? 1 and 10 short ; 2-4 equal, and about 

 twice as long as 10 ; 5, 6, and 9 mutually subequal, and little longer than 4; 7 and 8 

 mutually equal, and longer by as little than 6. Flight chiefly late in the evening and 

 nocturnal. Subimago usually quiescent about twenty-four hours, standing upon its 

 hinder legs with the fore legs mutually subparallel and horizontally prorect, the seta^ 

 close together, and the wings erect. Nymph latent ; tracheal branchiae all double and 



