EEV. A. E. EATON ON RECENT EPHEMERID.E OR MAYFLIES. 237 



EPEORUS, Etii., 1881 ; restricted [in PI. XXIY.] 1883. 



Illustrations. Adult (details), PL XXIV. 44 A. Nymph, PI. LVI. 



Adult. — First joint of the liiud tarsus rather longer than the second; first joint of the 

 fore tarsus commensurate with tlie second joint; ungues of the 6 fore tarsus alike and 

 obtuse ; penis lol^es of moderate breadth, joroduced outwards a little at their extremities. 

 Fore leg of 6 about as long as the body : tarsus about l,y as long as the tibia, and this 

 about IJ as long as the femur ; the tarsal' joints in order of shortening rankl equal to 2, 

 3, 4, 5. Pore leg of 2 about yo as long as the body ; tarsus about | as long as the tibia, 

 and this about x| ^^ long as the femur ; the tarsal joints rank as in tlie other sex. Hind 

 tarsus of 6 about f as long as the tibia, and this about i as long as the femur ; joints 

 1-4 of the tarsus diminish successively in length by small gradations. Ungues of the 6 

 fore tarsus alike, broad and obtuse; those of the hinder tarsi and also of the ? fore 

 tarsus each unlike the other. Hind wings of ordinary form ; the axillar region narrow^ 

 but Avith sutficient neuratiou. In the 2 abdomen the relative lengths of the dorsal 

 segments 2-10 may be formulated thus : — 7, 9, 12, 12, 12, 10, 10, 5, 5 ; ventral lobe of 

 the ninth segment refuse. Porceps-basis of the S produced behind into short divergent 

 lobes for the support of the forceps-limbs ; the short proximal joints of the limbs 

 combine with the second joints so as to constitute a gibbous enlargement at the base of 

 each limb. The seminal ducts terminate near the extremities of the penis-lobes ; stimuli 

 not obvious. Outer caudal setae of 6 about thrice, of ? 2.^-3 times, the length of the 

 body. Vertex of ? head transverse; the edge of the occiput ascends from the middle 

 towards the posterior orbits of the oculi in even curves ; median ocellus somewhat 

 isolated, moderately prominent, in dried examples, below the front border of the upper 

 surface of the head. Pronotum of 2 excised, or sometimes cordately excised in the middle- 

 behind ; the reflexed lateral lobes rounded below and somewhat straightened beliind. 



Subimafjo. — "Wings tinted wath greyish ; the neuration opaque ; the bordering of the 

 cross veinlets (when developed) inconspicuous. During repose the insect prorects its 

 fore legs a little apart, and the seta? are only separated to a small extent. 



Nymph. — Abdominal tracheal branchiae obliquely rcclinate or decuiubent at the sides, 

 with short scanty suberect fasciculate fibrils ; lamina; of the foremost pair far apart, each 

 a little longer than broad and obliquely ovate ; hinder lamin;^ nearly uniformly oval,, 

 with the outer or inferior margins thickened and ciliate ; the fourth lamina on each 

 side is the longest, and those anterior to it diminish successively in size less than the 

 three that follow : branchial trachege well defined, laxly and delicately arborescent, 

 distributed chiefly towards the thinner parts of the lamina?. Median caudal seta totally 

 absent; the two little longer than the body, and glabrous. Pronotum well defined, 

 truncate posteriorly ; its lateral ])orders undilated, rounded off at the front corners, but 

 subparallel behind. Pangs of the maudiljles unequal, compressed, denticulated at the 

 tips ; the exterior fang broad and only moderately acute ; the interior fang much shorter 

 and smaller; endopodite absent, represented only on the left mandible by an incon- 

 spicuous tuft of hairs. Lacinia of maxilla i. nude externally, and terminated Ijy three 

 subequal subulate fangs ; first joint of the palpus stout, enlarged only slightly towards 



SECOND SEEIES. — ZOOLOGY, VOL. III. 32 



