Mayfly Species Isonychia serrata (Slate Drakes)

A species having purplish brown markings on a bronze abdomen, and dark venation.

Head brown. A black mark below the frontal margin. Reddish purple spot on each side of median carina; another on outer side of base of antenna. Pronotum brown. Mesonotum yellowish brown margined with cream color; a yellowish spot anterior to the scutellum, which is dark brown. Metanotum and sternum dark brown. Pleura pale with brown and purplish markings. Fore leg purplish; femur grey at base and apex; tarsus light greyish purple. Distal half of last joint of fore tarsus and base of claws purple. Middle and hind legs white, last tarsal joint and claws purplish grey. Venation dark purple brown.

Abdomen bronze dorsally, the posterior half of each tergite purplish brown; wide dark posterior margins. A paler mid-dorsal line is present, bordered by oblique dark submedian streaks. Pleural fold and postero-lateral angles very dark brown. Ventrally dark purplish brown, except for the pale antero-lateral angles, a very narrow pale posterior margin bordered by the dark central color, an oblique pale submedian dash and four pale dots arranged transversely across each sternite near the center. On sternites 6-9, the lateral margins are also pale. Narrow dark bar parallels the pleural fold posteriorly on each sternite; at its anterior end is a dark dot. Tails very dark brown, slightly paler distally. In basal portion, joinings slightly paler brown. Forceps and forceps base yellowish or bronzy brown. Forceps base very slightly excavated on its apical margin; penes of the Isonychia arida type, the incurved lower portion bearing 7-8 saw-like teeth (see fig. 125).

In female, purplish markings at the corners of the occiput and between the eye and the lateral ocellus. Subanal plate of female almost straight across the apical margin, its outer angles rounded.