Mayfly Species Epeorus lagunitas

Closely allied to I. albertae (now a synonym of Epeorus albertae), but with slight differences in genitalic structure; fore femur shorter than tibia.

Head purplish brown. Thorax light red-brown, pronotum extensively shaded with purplish brown. Faint traces of a darker median stripe on mesonotum, as in albertae. Scutellum and lateral areas just anterior to it darker red-brown; outer margin of dark area, and median area anterior to scutellum, yellowish. Posterior margins and lateral depressions below scutella on mesothorax and metathorax also dark brown. No distinct blackish markings on pleura; faint purplish shading below wing roots and an oblique purplish streak anterior to root of fore wing. Legs olive brown. Fore femur somewhat yellowish near base, and with faint reddish tinge; tibia and tarsus smoky. Apex of fore tibia, tarsal joinings, claws and distal tarsal joint blackish. An indistinct purplish brown mark near middle of each femur; the area on each side of it is shaded with purplish, on middle and hind legs. Fore femur about 3/4 the length of tibia. Fore claws similar, blunt. Wings hyaline; venation light brown. Humeral cross vein purplish black near subcosta, pale at costal margin. Basal costal cross veins rather weak, especially at costal margin. Cross veins between bulla and stigmatic area obsolescent. Stigmatic veins well developed, about 10 in number, not anastomosed. A faint brownish stain in stigmatic area.

Abdominal segments 2-7 semi-hyaline, yellowish; tergites more or less distinctly tinged with pale brownish. Posterior margins of tergites and lower edge of pleural fold darker brown. In one paratype, sternites likewise faintly shaded with brown. Segments 8-10 opaque, rather bright red-brown; sternites rather paler than tergites. Tails dark yellowish brown; very inconspicuously darker at joinings. Apical margin of forceps base very slightly convex. A distinct swelling, somewhat conical, near base of long joint of forceps, on inner margin. Penes very similar to I. albertae, but with longer and more slender median spines; lateral beak-like appendages on each division of penes slightly longer and more slender (see fig. 107).

Distinguished from I. albertae by the relatively longer fore tibia and by genitalic differences noted above. The lack of distinct blackish pleural markings separates it from I. youngi (now a synonym of Epeorus albertae) and I. sancta-gabriel (now a synonym of Epeorus hesperus).

Female very similar to male, aside from usual differences. Basal costal cross veins better developed.