Mayfly Species Callibaetis californicus (Speckled Duns)

A reddish brown species; wing of male not pigmented.

Head and thorax of male dark reddish brown. Fore femur reddish brown; tibia paler red-brown, darker distally, blackish at femoro-tibial joining; tarsus yellowish, joinings narrowly brownish. Middle and hind legs yellowish white; femora with a prominent pre-apical reddish brown band, and streaked longitudinally with red-brown in distal half; 6 to 8 round reddish brown dots along the middle area of each. Tibiae blackish at femoral joining; distal tarsal joint red-brown, other joints reddish apically; joinings narrowly red-brown. Head and thorax of female paler red-brown except the postero-lateral areas of mesonotum; stippled with reddish brown. Fore leg yellowish white, the dark reddish brown femoral band very prominent; apex of tibia, and all of the tarsus except the basal joint, reddish.

Wings hyaline; cross veins few in number (18 to 22 beyond first branch of radius) marginal intercalaries single (see fig. 161); longitudinal veins pale yellowish brown in both sexes; cross veins yellowish in wing of male, and in female wing beyond the disc; those in disc of female wing snowy white. Wing of male not pigmented. Vitta in wing of female rather dark reddish brown, including the basal costal space; cross veins fenestrate with hyaline, those in the costal space to beyond the middle being “short bands from vein to costa,” rather than the usual round or oval spots. Hind margin of vitta “with about 8 or 10 indentations,” those in the basal half quite wide. Hind wing rather narrow for its length, and narrowed toward the tip; reddish brown at extreme base. Cross veins only moderately numerous; usually no marginal intercalary; the costal border distinctly emarginate immediately behind the basal projection.

Abdomen of male reddish brown, paler yellowish brown ventrally; tergites with paler lateral and posterior margins; anterior margin of each very narrowly darker; an indistinct darker line marks the spiracular area; traces of a pale mid-dorsal line. On each tergite and sternite, a pair of reddish brown oblique submedian streaks from anterior margin about to the middle of the segment; one or two dark dots in a line with each dark streak, immediately posterior to it. Median and lateral areas of each segment with red-brown stippling, the dots not very close together. Abdomen of female paler, flesh-colored, but similarly marked. Forceps reddish brown at base, yellowish apically. Tails whitish, joints relatively very long; alternate joinings purplish brown.

Longitudinal veins pale yellowish brown in both sexes; cross veins yellowish in wing of male, and in female wing beyond the disc; those in disc of female wing snowy white.

Abdomen of female paler, flesh-colored, but similarly marked.