EEV. A. E. EATON ON EECENT EPHEMERID^ OR MAYFLIES. 51 



the ground-colour ranging from very light yellow-ochreous, or very light Mars-yellow, 

 to light yellowish raw-umber ; and the markings from pitch-black and intense burnt-umljer 

 brown to a slightly yellowish modification of intense Roman sepia-brown, approaching raw 

 umber. The dominant pattern of the darker markings is, on the dorsum, a median 

 longitudinal stripe and a diagonal lateral stripe extending from the stigma to the hind 

 margin of every intermediate segment ; that on the venter, in nearly every segment, is 

 a pair of stripes extending, one on each side, from the hinder angles of the segment (or 

 thereabouts) to the base of the segment, convergent towards each other, and in indirect 

 continuity Avith the oblique dorsal stripes of the following segment. Some examples 

 simply display this dominant pattern, and in them the light ground-colour in segments 2 

 to 8 is shown on each side of the median stripe in the form of two right-angled triano-ular 

 spots occupying the upper anterior and the lower posterior halves of the space diagonally 

 intersected by the lateral stripe ; in segment 9 the lower posterior compartment is 

 obscured ; segment 10 has a small dark spot at the base in the middle, and no lateral 

 stripes; the midribs of the subanal lobes are pitch-black. This dominant pattern 

 undergoes the folloAving modifications in individual specimens. The median stripe in 

 segments 2-5 is dilated posteriorly so as to form a triangular sj)ot in every segment ; the 

 triangular compartments of the quadrangular areas on each side of the median stripe 

 have the angles adjacent to the diagonal stripes filled up with the dark colouring, so as to 

 restrict the lighter ground-colour to oval spots above and ovate or linear spots below the 

 diagonals, or to quadrangular spots in the anterior segments, and semiovate spots in the 

 hinder segments above the diagonals, and a narrow bordering along the spiracular margin 

 below the diagonals ; in some examples the pale colouring below the diagonals is re- 

 stricted almost completely to the hinder lateral angles of the dorsum ; the additional 

 colouring is apt to convert the latero-dorsal markings on each side into a broad zig-zag or 

 serrated stripe. On the venter, the spaces included by the two convergent stripes, and 

 the hinder border of nearly every segment are sometimes sufiiised Avith the darker 

 colouring, leaving a light-coloured triangular space on each side of the segment external 

 to the stripes ; when this is not so, the stripes are sometimes dilated behind. There are 

 often dark spots at the ganglia. Sette variable in colour, their joints either uniformly 

 or in a large measure bistre-, burnt-umber, or warm sepia-brown, often pale or light- 

 ochraceous anteriorly, sometimes lighter at the joinings only, rarely dark and opaque at 

 the joinings ; all of the joints in the same individual specimen are much alike in coloration. 

 Eore leg from trochanter to ungues usually in opaque view dark burnt-umber, changing 

 with transmitted light to madder-brown, the first tarsal joint, the ends of the other tarsal 

 joints and that of the tibia opaque ; sometimes they are pitch-brown, or even bistre- 

 brown, with the whole of the tarsus lighter and changing Avith transmitted light to warm 

 sepia-grey ; sometimes the basal portions of the intermediate tarsal joints are in a large 

 measure whitish ochraceous, or the tarsus is nearly uniformly sepia-grey • one example 

 has the tibia pitch-brown, black at the tip, the trochanter and femur intense bistre-brown, 

 lighter above towards the base of the femur, and the tarsus light bistre-brown, with the 

 first and terminal joints and the extremities of the intermediate joints pitch-black, the 

 bistre changing in transmitted light to raw umber. Hinder legs in opaque vicAV, flavescent 



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