Labiobaetis sonajuventus, Webb, J. M., 2013

Webb, J. M., 2013, A new species of Labiobaetis Novikova & Kluge, 1987 (Ephemeroptera: Baetidae) from Washington, USA, Zootaxa 3750 (1), pp. 95-99 : 95-98

Labiobaetis sonajuventus n. sp.

Material examined: HOLOTYPE: 1 nymph, USA, Washington, Okanogan County, Loup Loup Creek, 48.47593° –119.767434°, 3 August, 2012, coll: S. Dunphy [INHS]. PARATYPES: 10 nymphs, same data as holotype (parts of 2 mounted on slides, one in CMC-10, one in Canada Balsam) [INHS]; 10 nymphs same data as holotype [PERC]. Additional material examined. 69 nymphs, same data as holotype [author’s personal collection].

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 L. frondalis but differs in the more distinctly convex outer margin of the palp and the relatively smaller labial palp segment III (Morihara & McCafferty 1979b: Fig. 29c). Additionally, L. frondalis is not known any further west than eastern South Dakota and southeastern Texas (Morihara & McCafferty 1979b; Wiersema 1998; Guenther & McCafferty 2008). Labiobaetis apache is superficially similar to L. 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 L. apache , which can be up to 8mm in length. The original description incorrectly states L. apache to be 5–6mm, but some paratypes are 8mm.

Nymph description. Body Length: up to 5 mm; caudal filaments: damaged in all specimens. General color uniformly brown (Figs. 1,2).

Head: Brown, paler around eyes and between bases of antennae. Intra-antennal area with distinct keel ( Fig. 3 ). Antennae brown; scape and pedicel with numerous fine setae and scales, scape with distinct lobe. Labrum nearly square, with 0+8–11 submarginal setae, submarginal setae pointed and widest subapically, submarginal setae evenly spaced, dorsal surface with numerous fine setae ( Fig. 4 ). Right mandible ( Fig. 6 ) planate, area between incisors and mola slightly convex and with numerous minute spines; prostheca robust; incisors fused, with 3(1)+1+3-4 denticles. Left mandible ( Fig. 5 ) angulate, area between incisors and mola sinuate and with numerous minute spines; prostheca robust; incisors fused, with 3(1)+1+3-4 denticles. Maxilla ( Fig. 7 ) with two segmented palp, slightly exceeding length of galea-lacinia, second segment with barely discernible subapical excavation, slightly longer than segment I. Labium ( Fig. 8 ) with palps three segmented; segment II strongly expanded distally on medial margin, outer margin distinctly concave, medial margin nearly straight and lobe with numerous fine setae and row of three stouter setae near lateral margin; segment III rounded to slightly pointed, base subequal to one-half distal width of segment and with numerous fine setae and pointed robust setae, approximately 0.3 times as long as segment II; paraglossae much wider than glossae, with three rows of marginal setae and subapical oblique row of setae on ventral surface.

Thorax: Pronotum brown with two indistinct pairs of pale spots. Mesonotum uniformly brown. Sterna pale brown. Hind wing pads present. Femora with single, sparse row of medium pointed setae on dorsal margin, subapically with 2–3 setae, apically with several medium pointed robust setae and fine setae; anterior surface with numerous sharply pointed robust setae, most numerous ventally and basally; ventral margin with numerous short robust setae, villipore absent or poorly developed on all legs. Tibiae with two rows of medium robust setae on inner margin, scattered row of short robust setae on outer margin and scattered short robust and fine setae on other surfaces. Tarsi with single row of medium robust setae on inner margin, scattered row of short robust setae on outer margin and scattered short robust and fine setae on other surfaces. Tarsal claw with row of ~17 evenly sized denticles.

Abdomen: Abdominal terga brown with indistinct pair of submedian pale dots and anterior longitudinal streaks, slightly paler laterally, with scales, scale bases, and fine setae; posterior marginal spine length subequal to width; posterior margins with sharply pointed spines, lateral margins without fringe of robust setae. Sternum pale brown to brown, posterior margins of sterna VII–IX with triangular spines. Gills missing on all specimens, gill sockets present on segments I–VII. Paraprocts with numerous long sharply pointed marginal spines and scales and fine setae on surface. Caudal filaments three, broken on all specimens.

Adults: unknown.

Etymology. The specific epithet is an allusion to the recently disbanded music group, Sonic Youth and is derived from the Latin nouns sonus (=sound) and juventas (=youth).

Figures

FIGURES 1 – 4. Labiobaetis sonajuventus n. sp. 1, dorsal habitus; 2, lateral habitus; 3, head capsule, anterior; 4, labrum, detail of submarginal setae, with two setae outlined in black.

FIGURES 5 – 8. Labiobaetis sonajuventus n. sp. 5, left mandible, ventral; 6, right mandible, ventral; 7, maxilla; 8, labium.