Mayfly Species Dentatella coxalis

A species of the bicolor group (now a synonym of Eurylophella bicolor). First seven abdominal tergites heavily shaded with light brown and black; black spots on coxae, trochanter and femur.

Eyes ruddy brown. Head yellow. Thorax brown, brighter on the posterior part of the mesonotum; pleura with yellow shading. Legs rather bright yellow; two black spots on each coxa, and an apical black spot on each trochanter and femur, most distinct on the middle and hind legs. Wings hyaline; venation hyaline. The first seven abdominal tergites are heavily shaded with light brown and black; on tergites 1-4 only pale median patches are left unmottled. In each pale patch is a black median mark, and dark submedian shading. Tergites 5-7 have larger pale areas in which the dorsal streak is lacking, but the submedian streaks are prominent. Black streaks in the region of the spiracles. Tergites 8-10 are light brown with submedian dark marks anteriorly, and lateral dark streaks. Pale yellowish white ventrally; sternites 1 and 9 are shaded with brown. Ganglionic areas brown. Tails white, unmarked.

A nymph tentatively associated with the above imago is paler in color than other related species, with the head tubercles, antennae and dorsal spines prominently white. Head and thorax are sprinkled with pale dots; abdomen is light brown dorsally, with yellow and black lateral markings and traces of dark submedian marks along the rows of dorsal spines. Legs pale yellowish, the light brown bands with numerous pale spots. Occipital tubercles not prominent. The rows of dorsal spines diverge to rearward; those on tergites 1-3 are broad, short and blunt, and bend backward gently. The postero-lateral spines on segments 2 and 3 are moderately well developed; those on segments 4-7 are long, narrow and incurved. The operculum usually has a pale oval patch near the middle; the joint is pale; dark longitudinal veining is faintly present. Venter of abdomen pale, with the usual curved row of dark dots. Tails light brown, with only very faint traces of pale cross bands.