Mayfly Species Diphetor hageni (Little Blue-Winged Olives)

Abdominal tergites 2-6 of male imago hyaline whitish; genitalia of the Baetis intercalaris type, tubercle present on inner margin of basal forceps joint. Second vein of hind wing forked near base.

Head and antennae light red-brown. Turbinate eyes moderate in size; stalk yellowish, upper surface pale orange in alcoholic specimens. Thoracic notum rather dark reddish brown; margins of scutellum blackish. Pleura and sternum somewhat paler red-brown; intersegmental areas of pleura yellowish. Legs whitish; fore femora yellowish, other femora faintly yellow-tinged; coxae reddish brown. Wings hyaline, venation pale. A faint cloud in the stigmatic area of the fore wing; cross veins 6-8 in number; aslant, no apparent tendency to fork, sometimes incomplete toward the subcosta; between them, many granulations. Marginal intercalaries much as in B. parvus (now a synonym of Diphetor hageni). Hind wing very similar to that of parvus (see fig. 163).)

Basal segment of abdomen dark reddish brown dorsally, paler ventrally. Abdominal segments 2-6 hyaline, white. Spiracles outlined in black; geminate blackish tracings along the entire spiracular area; on the basal sternites especially, short oblique branches extend out from the main spiracular line. Segments 7-10 light reddish brown, opaque; sternites slightly paler than tergites; posterior margins of tergites and sternites darker red-brown, presenting an annulate appearance. Tails and forceps white. At the inner apical margin of the basal forceps joint is a distinct tubercle or inward projection; inner margin of this joint somewhat irregular. Apical joint of forceps relatively shorter than in parvus, being about one-third the length of the penultimate one (see fig. 164).

Described as B. parvus

Body length 5.5 mm, wing length 5-5.5 mm

Abdominal tergites 2-6 of male imago hyaline, whitish, unmarked; genitalia of the Baetis intercalaris type, no tubercle on inner apical margin of first forceps joint. Second vein of hind wing forked near base.

Head and thorax deep blackish brown; filament of antenna paler. Turbinate eyes moderate in size; both stalk and upper surface dark orange brown, in dried specimens. Paler red-brown areas on pleura below the wings; tip of scutellum paler brown. Legs whitish. Wings hyaline, venation pale. 5-8 cross veins in the stigmatic area of the fore wing, often with short horizontal veins between them, aslant, often incomplete on the subcostal margin, sometimes forking toward the subcosta. Usually one short intercalary in the first interspace; those of the second interspace slightly shorter than the following pairs. Hind wing unusually wide for its length; costal projection well developed. Three longitudinal veins, the second forked near the base; one long intercalary in this fork (usually also a pair of short intercalaries just below the anterior branch, not shown in Dr. Dodds’ sketch; traces of another short one between the long intercalary and the posterior branch, in some specimens).

Basal tergite of abdomen wholly dark brown, sternite somewhat paler. Abdominal segments 2-6 hyaline white; usually no dark spiracular markings. Tergites 7-10 opaque, brown; wholly or in part suffused with deep rose-color. Sternites opaque creamy white, more or less shaded and marked with rose. Tails white. No tubercle or projection on the inner apical margin of the basal forceps joint. Apical joint of forceps fully half as long as the penultimate one.

The forked second vein of the hind wing distinguishes this species from all other described North American species excepting B. devinctus (now a synonym of Diphetor hageni); the presence of a well-developed tubercle on the inner margin of the basal forceps joint, as well as the paler thorax, separates devinctus from parvus.

Head of female yellowish. Thorax reddish brown. Legs wholly pale whitish. Abdomen yellowish, the tergites more or lees washed with pale purplish or rose-tinged brown: intersegmental areas pale.