Mayfly Species Traverella presidiana

This is a clear-winged blackish-brown species with nearly white abdomen. Head very dark brown including the very broad and contiguous upper eyes, and the basal segment of the antenna.

Thorax brown, darker around the margins of the dorsum, with three subparallel obscure pale lines on the mesoscutum that converge into a pale streak on the front of the scutellum. Sides and leg bases paler (remainder of legs lacking). Wings hyaline, with a tinge of amber on their extreme bases, that in the fore wing diffuses outward along the radial vein toward the bulla. Beyond this, the longitudinal veins are but little more evident than are the faint cross veins. In the stigmatic area the cross veins are weak, simple, and scarcely aslant.

Abdomen faintly brownish or yellowish-white above and below, with a wash of brown on the dorsum of segments 1 and 7 to 10, and with a touch of the same on the lateral margins of some of the intervening segments. Forceps broken off the one known specimen. The pair of internal processes that overlie their base in this species are very long, linear and slender, longer than the penes, so that their finely denticulate tips project into view to rearward. Penes short, separated by a V-shaped notch; in form pyramidal, their apices truncated, their reflexed spurs minute, slender, awl-shaped, their incurving tips lying across the base of the interpenial cleft (see fig. 146).