Mayfly Species Ironodes arctus

Thorax darker red-brown, penes more slender than in allied species; abdominal segments reddish.

Eyes of male large, contiguous apically. Head purple-brown. Thorax dark red-brown; mesonotum almost black-brown. Paler red-brown areas on pleura; depressions on each side of scutellum black-brown. Fore legs red-brown; femora yellow-tinged; apex of tibia, and tarsal joinings, blackish. Middle and hind legs paler red-brown, with yellow tinge; tarsi deep smoky; claws and all joinings darker. Wings hyaline; venation dark red-brown; stigmatic area not brown-tinged. 6 to 7 basal costal cross veins; about 9 stigmatic veins, simple, almost straight.

Abdominal segments 2-7 semi-hyaline, light red-brown; anterior fourth of each whitish hyaline, except sternite 7, so that abdomen appears annulate. Pleural fold red-brown. Posterior margins not noticeably darker or more opaque than preceding area, except slightly on dorsal portions of tergites. Segments 8-10 opaque, darker red-brown. Tails dark red-brown. Penes (see fig. 109) more slender than in Irondes lepidus and with no such subapical spines as in that species. Second joint of the forceps much as in Ironodes nitidus. Two small spine-like structures between bases of penes may be artifacts.