Mayfly Species Siphloplecton basale (Pseudo-Gray Drakes)

A dark species; cross veins of costal area and disc of the fore wing heavily infuscated; a brown cloud at the base of each wing, and at the bulla of the fore wing. Frons pale; remainder of head blackish brown. Thorax deep black-brown, with a slight ruddy tinge. Fore legs reddish brown; a dark subapical femoral band, black knees, and darker tarsal joinings and tips of tibiae. Femora of middle and hind legs similar but paler; tibiae and tarsi paler, yellowish. A dark cloud at the base of each wing; cross veins of fore wing dark brown, those of the costal margin and the wing disc rather heavily margined; a brown cloud at the bulla, often a faint cloud in the stigmatic area, also at fork of hind branch of the radial sector. Wing of female with no such basal dark clouds. First segment of abdomen wholly dark brown; tergites 7-10 largely dark brown, 7 and 8 with pale antero-lateral angles, 10 pale laterally. Tergites 2-6 semi-hyaline, rather extensively shaded with dark brown on the posterior and lateral margins and the dorsal area; anterior margins, antero-lateral angles and lateral area pale. A curved line of black pencilings on each side of each tergite, and a dark brown oval patch on each side near the median line. Sternites 2-8 largely pale, semi-hyaline, with a reddish brown dot on each side of the median line, on each; sternite 9 dark brown with a pale streak on each side; ganglionic areas dark brown, most prominent on the apical segments. Tails whitish, joinings ruddy brown. Genitalia largely pale reddish brown. Penes as in fig. 115.

Described as S. signatum

Body length 14 mm, wing length 11.5 mm

In this species the wing is very similar to that of S. basale; the body differs from the latter in the much paler thorax and abdomen.

Frons greyish white; remainder of head pale brown. Pronotum dark brown, its posterior margin whitish. Mesonotum yellowish brown; scutellum margined with dark reddish brown; metanotum dark brown. Pleura yellowish, sutures brown. Fore femur light brown; tibia and tarsus yellowish white. Middle and hind legs pale yellowish brown; dark bands apically on all femora; tarsal joinings and tips of tibiae slightly darker. Abdominal tergites 1 and 2 largely brown; tergites 3-6 much paler than in basale, largely whitish and rather opaque. Brown markings on these tergites are reduced to a median triangle and lateral extensions of this, which do not quite attain the anterior margins; posterior margins are narrowly brown, and near the pale pleural fold is a brownish area. At the posterior margin of each tergite, a purplish mark on the median line and a lateral streak on each side of this. Tergites 7-10 largely dark reddish brown; pale antero-lateral areas on tergites 7 and 8 are more extensive than in S. basale. Ventrally wholly pale, except for a minute dark dot on the median line, at the anterior margin, and indistinct tan bars running forward from the posterior margin, parallel to the median line. Tails pale, joinings reddish brown. Genitalia light brown; penes as in fig. 115.

The gills of the nymph are double on segments 1-3. On the venter of the abdomen are three uninterrupted longitudinal brown lines, one median and two lateral. The claws of the second and third legs are almost as long as the tarsi.