Mayfly Species Nixe horrida

Mesonotum light brown; abdominal tergites light brown, median area paler but with no mid-dorsal pale line; genitalia of the lucidipennis (now a synonym of Nixe lucidipennis) type.

Head light brown, extreme frontal area yellow; a round black spot below lateral ocellus and near the eye, as in H. perfida (now a synonym of Nixe perfida). Thoracic notum light brown, becoming deeper in the region of the scutellum; posterior edges of mesonota and metanota blackish. Pleura and sternum light ochreous, not as yellow as in perfida; brown shading at bases of legs. Legs light ochreous; fore femur strongly tinged with reddish brown in the apical half, other femora with slight ruddy tinges in this area. Wings hyaline; longitudinal and cross veins pale.

Abdominal tergites light brown, the median area paler and the lateral area darker, but the pale mid-dorsal streak and postero-lateral triangles of perfida are not present in this species. Posterior margin of each tergite dark brown; sternites light ochreous. This species is most nearly allied to H. perfida, from which it may be distinguished as indicated above; also the apical margin of the forceps base is less deeply emarginate and lacks the lateral projections; details of penes somewhat different (see fig. 96, after McDunnough). Length of forceps joints as in that species.