Mayfly Species Acentrella insignificans (Tiny Blue-Winged Olives)

Abdominal tergites 2-6 of male imago pale, semi-hyaline, considerably tinged with smoky brown; genitalia of the modified moffati type (now a synonym of Baetis tricaudatus); no costal projection on the hind wing, which has two veins only.

Turbinate eyes small, rather bright red. Thorax deep brown. The pleural sutures and the anterior projection of the metanotum are pale cream-colored. Fore femora dull smoky brown, tibiae and tarsi paler. Middle and hind legs pale ochreous, with smoky tinges on the femora. Wings hyaline, venation pale. Only two veins in the hind wing; the costal projection is entirely wanting. Hind wing narrow and leaf-like.

Abdominal segments 2-6 pale, semi-hyaline, the tergites considerably tinged with smoky brown. Segments 7-10 opaque; the tergites light sepia-brown, the sternites whitish. Tails white. The second joint of the forceps somewhat cylindrical; fourth joint of the forceps longer and narrower than in B. dardanus (now a synonym of Labiobaetis dardanus), but not as long as in B. frivolus (now a synonym of Heterocloeon frivolum). Between the bases of the forceps is a short projecting plate, not found in dardanus.

Aside from the genitalic differences noted, this species may be separated from B. dardanus by the smoky tinges of the basal abdominal tergites, which are also lacking in B. propinquus (now a synonym of Labiobaetis propinquus); B. frivolus (now a synonym of Heterocloeon frivolum) and B. amplus (now a synonym of Heterocloeon amplum) are larger, darker species of the same group.