Mayfly Species Ephemerella tibialis (Little Western Dark Hendricksons)

A slender species probably allied to the Ephemerella needhami group; only the nymph is known; lateral extensions of the abdomen inconspicuous; dorsal spines present.

Head and thorax smooth. Maxillary palp weak but perfect in form. Antennae pale. General color pale reddish brown. Wing pads and the mesonotum anterior to them dark brown in mature nymphs. Legs pale, with no conspicuous markings. 6 to 7 denticles on each claw. Hind leg rather long.

Abdomen relatively long and slender; middle segments slightly wider than the basal and apical ones. Lateral extensions inconspicuous. Postero-lateral spines on segments 4-9. Gills borne on segments 3-7. Dorsal spines present on tergites 2-8; short and inconspicuous on 2 and 3, well developed on 5-7. Anterior margin of each tergite pale. Posterior margin often narrowly dark brown; remainder reddish brown. Rather large lateral patches may be present next to the gills on the middle segments. No definite ventral markings. Tails pale, almost bare at base and tip, and with only a few short spines in the middle area; in mature nymphs, with narrow dark half-rings at the base

A member of the serrata group (now a synonym of Serratella serrata); abdominal segments of male translucent whitish on the anterior margins; tails deep smoky; fore tibia twice as long as the femur.

General color of male imago deep purplish brown. Thorax almost blackish dorsally. Fore femur pale smoky yellowish, tibia deep smoky, tarsus paler than the tibia; tibia fully twice as long as the femur. Middle and hind legs dull yellowish, the femora with reddish bands apically. Wings vitreous; venation pale grey-brown, the cross veins rather more distinct than is usual for this group. Anterior margins of abdominal segments 3-8 narrowly whitish, translucent. Sternites with indications of dark ganglionic blotches. Forceps reddish basally, blackish distally. Penes blackish (see fig. 156). Tails deep smoky, slightly darker at the joinings.