Triarthron lecontei, Horn, 1868

Peck, Stewart B. & Cook, Joyce, 2009, Review of the Sogdini of North and Central America (Coleoptera: Leiodidae: Leiodinae) with descriptions of fourteen new species and three new genera, Zootaxa 2102 (1), pp. 1-74 : 8-11

Triarthron lecontei, Horn, 1868

( Figs. 1 , 8–13 , 14 )

Triarthron lecontei Horn, 1868: 131, 1880: 279 ; Hatch 1957: 26.

Triarthron cedonulli Schaufuss, 1882: 43 . Synonymized by Horn 1883: 284.

Triarthron pennsylvanicum Horn, 1883: 284 , new synonymy.

Type material. Holotype of T. lecontei : ♂, bearing white label "Cal", red label " HoloTYPE / 3007", red label "M.C.Z. / Holotype 33555", white handwritten label " Triarthron / lecontei Horn ", and our red holotype label; seen and dissected (in Horn collection, MCZC). Type locality: "high Sierras east of Visalia, California ".

Type of T. cedonulli originally in “Museum Ludwig Salvator, Dresden”; possibly now in Berlin or Hamburg. Not seen. Type locality: Cisco and Sacramento , California .

Holotype of T. pennsylvanicum : female, bearing white label "Pen", red label " HoloTYPE / 3008"; red label "M.C.Z. / Holotype 33556"; white handwritten label " Triarthron / pennsylvanicum Horn "; and our red holotype label; seen and dissected (in Horn collection, MCZC). Type locality: Hazleton , Pennsylvania.

Additional material examined. We examined 211 specimens (See Appendix).

Diagnosis. Body elongate-oval, yellowish to reddish brown, shining. Length of pronotum + elytra = 2.4–3.6 mm (males), 2.3–3.7 mm (females); pronotum broad, ratio length:width = 1:1.6; elytra of medium proportions, ratio length:width = 1:0.7. Antennal club ( Fig. 8 ) moderately broad, ratio club width:length = 1:2.8; antennomeres 6 and 7 equal in width, width ratio of antennomeres 6:7:8:9 = 1:1:1.2:2.0. Mandibles ( Fig. 9 ) moderately elongate; right mandible with an elongate sub-apical tooth and an additional poorly defined tooth on apical one-half of inner margin; inner margin of left mandible with a thin, narrow plate on apical one-half and a tooth on basal one-half. Profemur and mesofemur of both sexes serrulate on posterior margins; female metafemur serrulate on posterior margin; male metafemur ( Fig.10 ) with ventral region of posterior margin serrulate, dorsal margin with 3–6 small teeth, broad tooth-like lamina dorsally and ventrally at apex of posterior margin. All tibiae of male and female slender, of uniform diameter in apical three-fourths, not widened at apex, lacking distinct tarsal groove, outer margins spinose. Male. Aedeagus ( Fig. 11 ) with median lobe broad at base, evenly tapering to narrowly rounded apex. Parameres not reaching apex of median lobe, slender, with 3–4 apical setae. Female. Coxites ( Fig.13 ) moderately elongate, cylindrical, with subapical setae; styli elongate, inserted at apices of coxites, with elongate apical setae. Sternite 8 ( Fig. 12 ) rounded apically; anterior apophysis broadly triangular.

Taxonomic notes. Triarthron lecontei is highly variable, both within and between populations, in the following characters: strigulate microsculpture of head and pronotum (dense to absent); punctation of head and pronotum; elytra (glabrous to densely setose); lateral pronotal margins (rounded to angulate); outer margin of male metatibia (angulate or not); dentition of dorsal lamina of posterior margin of male metafemur (3–6 teeth); and shape of large tooth-like lamina at apex of male metafemur. These non-genital characters do not consistently vary in concert with one another. However, the characters of the aedeagus are consistent throughout the species range.

We have not found characters to separate this species from Palearctic T. maerkelii Märkel with the description and figures presented in Daffner (1983) but have not seen enough specimens to be confident that T. lecontei is a junior synonym.

Distribution. The species occurs in the north-central parts of western and eastern North America, and seems to be absent from the forested center of the northern part of the continent ( Fig. 14 ). We have seen specimens from Canada: the provinces of British Columbia and Ontario; USA: the states of California, Massachusetts, Montana, New Hampshire, Oregon, Pennsylvania, Virginia, Washington, and West Virginia.

Field notes and habitats. Adults have been collected in mixed and coniferous forests and collected most frequently by flight intercept traps or evening car netting, with a few at ultraviolet lights and in pitfall or Lindgren funnel traps.

Seasonality. Adults have been collected from March to August with most specimens in July.

Figures

FIGURE 14. Known North American localities of Triarthron lecontei (black dots). In this and all following maps, small white circles indicate major cities.

FIGURES 1–4. Sogdini, habitus photos. 1. Triarthron lecontei, total length 3.4 mm. 2. Hydnobius autumnalis, total length 3.0 mm. 3. Stereus arenarius, total length 3.4 mm. 4. Sogda obtusa, total length 3.4 mm.

FIGURES 8–13. Triarthron lecontei. 8. Right antenna, dorsal view. 9. Mandibles, dorsal view. 10. Male right metafemur and metatibia. 11. Aedeagus, dorsal view. 12. Female sternite 8, ventral view. 13. Female coxites and styli, ventral view. Scale bar = 0.3 mm (Figs. 11, 13), 0.5 mm (Figs. 8, 9, 12), 0.75 mm (Fig. 10).