Mayfly Species Baetisca lacustris (Armored Mayflies)

Abdominal tergites of male imago brown, sternites pale yellowish white; venation wholly pale.

Head and thorax brown; thoracic sternum pale brown. Legs pale yellowish white. Wings hyaline, venation wholly pale. Abdominal tergites brown; sternites pale yellowish white, contrasting strongly with the dark upper surface. Forceps yellowish white. Tails whitish, not darker at joinings.

The nymph has lateral but no dorsal spines on the mesonotal shield; the genae are not produced into spines; the frontal projections are small and rounded. The lateral mesonotal spines are very long and sharp. This species is distinguished from others in the genus by the wholly pale venation and the striking contrast in color between the dorsal and ventral surfaces of the abdomen.