Mayfly Species Stenonema luteum

Eyes pale green, in living insect. Head pale yellowish white anterior to ocelli; carina with faint oblique reddish streak; antennse narrowly red-ringed at base; Vertex yellowish to yellow-brown near ocelli; reddish brown oblique streaks posteriorly; a red-brown spot may be present behind median ocellus, and a narrow line at margin of eye. Pronotum and mesonotum very pale ochreous; scutellum broadly creamy white; pleura yellowish white; an area between fore and middle legs and a portion of mesosternum tinged with light brown. Anterior portion of metanotum creamy; light brown posteriorly, this area appearing as a dark basal band on the pale abdomen. Coxae streaked with smoky on anterior and posterior margins; a faint pinkish patch behind posterior black streak. Legs pale amber. Fore femur with smoky tinge; median and apical purplish red bands on all femora. Tip of fore tibia, claw and tarsal joinings smoky. Basal fore tarsal joint rather short, slightly less than 5 the length of second. Wings hyaline; stigmatic area of fore wing light amber with slight reddish tinges. Costa, subcosta and radius dark smoky amber; other veins blackish; cross veins well developed.

Abdominal segments 1-7 hyaline, whitish yellow; dorsal posterior margins of tergites crossed by narrow black lines. No spiracular dots. Segments 8-10 opaque, creamy white; tergites 8 and 9, sometimes anterior portion of 10, shaded with pink. Forceps pale; genitalia of the Stenonema pulchellum type. Tails pale, joinings smoky.

This species is distinguishable from allied forms by reason of its large size, pale coloration and lack of spiracular dots.