Mayfly Species Callibaetis skokianus (Speckled Duns)

A large pale species; cross veins of fore wing numerous; marginal intercalaries paired; wing of male pigmented.

Turbinate eyes of male large, egg-yellow; head pale brownish, margins whitish. Vertex of female with two pale brown longitudinal streaks. Prothorax pale brown; median sutures of mesonota and metanota pale, the former with a brown band on each side; brown spots on the sides inferiorly. Pleura irregularly speckled with brown. Legs yellowish white; femora dark at the apices, and with few or no freckles; tarsal joints dark apically, the distal one wholly brown. Costal band on fore wing of female reddish brown, covering the bases of all the veins proximally; narrowed regularly toward the apex, where it ends just before the wing tip; no posterior lobes; most of the cross veins fenestrate with hyaline except at the base; basal costal space interrupted brown and white. In the stigmatic area the band fades into a yellowish wash. In the male, this band is paler and usually ends just anterior to the yellowish stigmatic area. Cross veins very numerous, especially in the female; in this sex, about 70 are present behind costal vitta. Marginal intercalaries paired. Cross veins pale, longitudinal ones mainly brown. Stigmatic cross veins numerous, often anastomosed. Hind wing broadly rounded at tip, all veins brownish; usually a pair of well-developed marginal intercalaries.

Abdomen pale yellowish or flesh colored, thickly dotted with brown, tending to form a dark submedian stripe on each side of a paler mid-dorsal line. Above the spiracular line on each segment is a brown dash; a curved dark mark is present above the anterior end of each dash. Sternites paler than tergites, the dots more evenly distributed; a pair of brown submedian curved marks on each, those of 9 abbreviated. Forceps and tails white.

Vertex of female with two pale brown longitudinal streaks.

Costal band on fore wing of female reddish brown, covering the bases of all the veins proximally; narrowed regularly toward the apex, where it ends just before the wing tip; no posterior lobes; most of the cross veins fenestrate with hyaline except at the base; basal costal space interrupted brown and white. In the stigmatic area the band fades into a yellowish wash. Cross veins very numerous, especially in the female; in this sex, about 70 are present behind costal vitta.