Mayfly Species Epeorus permagnus

Larger than I. grandis (now a synonym for Epeorus grandis), with darker mesonotum; spining on ventral surface of each division of penes much more extensive.

Head deep brown; no dark band on frontal margin; shaded with black around bases of antennae and sides of median carina. Thorax almost unicolorous black-brown. A single short black streak anterior to wing roots. Area anterior to wing roots often yellowish. Fore femur black-brown, paler at extreme base; tibia and tarsus blackish red-brown. Middle and hind legs light red-brown; femora shaded extensively with blackish; tarsi slightly deeper in color than tibiae. Coxae and trochanters of all legs black-tipped. Wings hyaline. Costa, subcosta and radius yellowish at extreme base, costa yellowish also in apical third; remainder of these veins thickened, dark reddish to purplish brown. Other longitudinal veins finer, paler red-brown; cross veins still finer, yellowish to light red-brown. 11 to 12 basal costal cross veins, very faint; humeral cross vein pale.

Abdominal tergites largely yellowish to olive brown. Large black-brown patches occupy tergites 2 and 3, leaving margins and median line pale. Tergites 4 and 5 with more restricted dark central areas, the margins irregular; lateral and antero-lateral margins pale, mid-dorsal line obscured. Tergites 6-8 with black-brown median triangle based on anterior margin, its apex extending backward along median line about 3/4 the length of each tergite, leaving large pale postero-lateral triangles, with a small rounded brown mark in each. Tergites 9 and 10 more reddish brown; anterior margins narrowly black; black spot laterally on 9; median line and median area of posterior margin of 10 blackish. Sternites olive brown; basal ones shaded with red-brown. A rounded smoky spot near antero-lateral angle of each intermediate sternite, the two spots on each sternite connected by a smoky transverse band. Sternite 8 shaded with red-brown; 9 deeper brown, with greyish posterior and postero-lateral margins. Pleural fold greyish on all segments. Tails deep red-brown, almost black-brown at base; joinings narrowly paler. Forceps deep red-brown, paler apically. Penes light red-brown, with many small spines on ventral surface of each division (see fig. 111).