Mayfly Species Stenacron candidum (Light Cahills)

A species of the interpunctatum group; no dark bar in wing below bulla; no dark oblique streaks on pleura; stigmatic dots present, prominent; genitalia of carolina type (now a synonym Hexagenia limbata).

Eyes greenish, in living insect; of usual size, not small as in S. carolina. Head yellowish; black dot on edge of median carina, a short black dash below each antenna; posterior margin dark brown, two small dark dots above it. Prothorax yellowish; black oblique lateral streak on pronotum, also short dark mark near postero-lateral margin. Mesonotum dark red-brown; scutellum yellowish. Pleura and sternum yellowish; faint greyish pencilings above leg bases; no oblique dark streaks. Legs yellowish. Fore femur distinctly greenish, other femora more faintly so, in living insect. Blackish median and apical bands on fore and middle femora; median band lacking on hind femur. Apex of fore tibia, and tarsal joinings, blackish, apical joint of fore tarsus deep smoky. Basal fore tarsal joint fully 1/2 as long as the second. Wings as usual in this group, but with no black bar joining the margined cross veins below bulla. Very faint brownish stigmatic stain. Basal costal and subcostal cross veins slightly thickened but not margined.

Abdominal segments 2-6, and base of 7, hyaline; whitish. Stigmatic dots purplish black, very distinct. Posterior margins of tergites narrowly blackish, with rather distinct black dot at median line. Segments 8-10, and apical portion of 7, opaque; tergites pale red-brown, sternites yellowish. Tails white, not darker at joinings. Penes as in fig. 91; resemble carolina (now a synonym of Hexagenia limbata) in almost total loss of spines on lower lateral margin.

Female similar to male, except for usual differences. Thorax and abdominal segments yellowish. Median band on hind femur represented by a dark streak near upper margin. Narrow continuous dark line across frontal margin of head.

Thorax and abdominal segments yellowish. Median band on hind femur represented by a dark streak near upper margin. Narrow continuous dark line across frontal margin of head.

Nymph very similar to that of S. frontale (now a synonym of Stenacron interpunctatum) (see Pl. XXXIV). Differs in the following respects: no pale median spot on frontal margin of head; dark lateral markings on abdominal tergites more extended, joined laterally by a narrow dark bar to median dark areas, on tergites 2-3 and 5-7; postero-lateral spine on segment 9 appears very slightly longer.