Mayfly Species Choroterpes basalis

This is a blackish species with very dark grey-brown abdomen and a deep brown stain on the fore wing bases, extending well outward along the interspace between the subcosta and radius. Head brown above, including the antennae. Thorax blackish above and below, brown at the sides, with obscurely pale sutures. Legs tawny yellow, with submedian blackish rings on the femora, and with a wider mark of the same color on the knees. Tarsi whitish. Wings heavily stained with brown at base, the membranes being lightly tinged over the proximal half of the fore wing and nearly the whole of the hind wing. The longitudinal veins are darker than in the other species.

Abdomen dark greyish brown or blackish above, pale beneath. In fully mature males of this species, the pale markings of the abdomen are well nigh obliterated; the middorsal line is very narrow and two pairs of spots are very faint. The black hair-line on the lateral margin is interrupted only on the joinings of the segments. In old specimens there tends to appear a parallel, more obscure black line close above it and the two are sometimes conjoined on each segment before the spiracle. The ventral surface is pale with a large blackish U-mark covering the margins of the 9th sternite except in the rear. Forceps white beyond their enlarged base. Penes brownish (see fig. 140). Tails white.

Described as C. ferruginea

Body length 5.5 mm, wing length 6 mm

This is a reddish brown species with grey-brown abdomen and reddish wing bases. The head is brown above with paler antennae. Thorax nearly uniform reddish brown. Legs yellowish, becoming whitish on the tarsi; a distinct brown spot on the middle of the femur and a touch of the same color on the knee. Wings subhyaline to whitish, with a diffuse reddish brown tint covering a considerable area of the fore wing and most of the hind wing. Longitudinal veins near the costal margin brown, elsewhere invisible, as are all the cross veins. Abdomen grey-brown, becoming darker and reddish at the ends; pale translucent beneath except on the end segments. A very narrow mid-dorsal pale line that becomes obsolete at the rear is overspread on segment 4 and 5 by broad pale middorsal triangles; smaller triangles in the same position on 3 and 6. A continuous black line follows the lateral margin on segments 2 to 8, with a parallel interrupted pale line in the spiracular area immediately above it. Venter of 9 reddish at the sides. Forceps pale. Penes reddish. Tails white, sometimes faintly ringed with reddish brown toward the base; often wholly pale.