Mayfly Species Labiobaetis sonajuventus

Source: A new species of Labiobaetis Novikova & Kluge, 1987 (Ephemeroptera: Baetidae) from Washington, USA

Diagnosis. Nymphs are readily distinguished from all other North American Labiobaetis by the concave outer margin of labial palp segment II, the distinct intra-antennal keel, and the pointed, apically expanded submarginal setae on the labrum. The new species is most similar to nymphs of Labiobaetis frondalis but differs in the more distinctly convex outer margin of the palp and the relatively smaller labial palp segment III (Morihara & McCafferty 1979 b: Fig. 29 c). Additionally, Labiobaetis frondalis is not known any further west than eastern South Dakota and southeastern Texas (Morihara & McCafferty 1979 b; Wiersema 1998; Guenther & McCafferty 2008). Labiobaetis apache is superficially similar to Labiobaetis sonajuventus n. sp. due to the nearly uniformly brown abdominal terga, but differs by having hair-like setae on the labrum, the shape of the labial palps, and the absence of a keel between the antennae. The new species is also somewhat smaller than Labiobaetis apache, which can be up to 8 mm in length. The original description incorrectly states Labiobaetis apache to be 5 – 6 mm, but some paratypes are 8 mm. Nymph description. Body Length: up to 5 mm; caudal filaments: damaged in all specimens. General color uniformly brown (Figs. 1,2).