Mayfly Species Drunella walkeri (Large Blue-Winged Olive)

A blackish, yellow-legged species; imago very similar to E. tuberculata (now a synonym for Drunella tuberculata), but smaller, more slender, with fewer dark femoral dots, and no ventral dark dots.

Head and thorax deep blackish brown. Fore femur and tibia deep brown; tarsus deep amber brown. Middle and hind legs yellowish, the femora heavily shaded with ruddy brown. All femora sprinkled rather sparsely with black dots. Wings hyaline; venation pale yellowish. Abdomen deep smoky brown; middle segments semi-translucent, apical segments opaque, deeper brown. Basal and middle sternites somewhat paler than the tergites; dark triangles in the antero-lateral angles, but no curved row of dark dots. Tergites rather unicolorous, but somewhat paler laterally. Tails yellowish, joinings unmarked. Genitalia very similar to E. tuberculata (now a synonym of Drunella tuberculata) (see fig. 153).

Nymph very close to E. wayah (now a synonym of Drunella walkeri), but distinguished by the presence of a lateral prothoracic tubercle, wider femora and shorter dorsal spines.

Head of nymph with broad frontal shelf, notched on each side to receive the bases of the antennae (see fig. 151 c). No occipital tubercles; head somewhat roughened. A single small prothoracic tubercle on each side near the middle of the lateral margin. Anterior margin of fore femur with spines. All femora very much flattened, the posterior margin with a wide backward extension. Head, legs and body very hairy. Dorsal spines very minute. Ventral surface of abdomen rather less hairy than in E. wayah; no adhesive disc. General color pale greyish to deep olive brown; thorax, tibiae and tarsi with suffused darker markings. Usually a mid-dorsal row of dark blotches on the abdomen; ventrally, a lateral row of dark streaks on each side, but no curved row of dark dots between, as in E. tuberculata (now a synonym of Drunella tuberculata). Tails short, pale.

Described as E. wayah

Body length 6-7 mm

A member of the fuscata group (now a synonym of Drunella walkeri), and closely related to E. fuscata (now a synonym of Drunella walkeri). Distinguished from this species in the nymphal stage by the lack of prothoracic tubercles, better developed abdominal spines, slightly narrower femora, and somewhat longer tibial thumb. Head of nymph (see fig. 158 a) with a broad frontal shelf, widely notched on each side to receive the bases of the antennae. Frontal horns barely indicated. No occipital tubercles. All femora much flattened, but without the wide prominent posterior extension of E. fuscata; fore femur with spines on the anterior margin. Tibial spine almost one-third as long as the tarsus; blunt, stout, better developed than in fuscata (see fig. 159). Legs and entire body very hairy. No prothoracic tubercles, as in fuscata. Dorsal spines present,—not conspicuous, but better developed than in fuscata. Sternite 9 and the lateral margins of 3-8, very hairy, forming a very incomplete adhesive disc. General color (in life) grey-green; yellowish brown in alcohol. Marked irregularly with dark brown on legs, head, thorax and abdomen; tergites 8-10 usually yellowish. Abdominal sternites yellow; a lateral row of dark marks on each side, much as in E. serrata (now a synonym of Serratella serrata).