Sigmoria stenogon Chamberlin 1942

Sigmoria stenogon Chamberlin Figs. 55-60, 132-133
Sigmoria stenogon Chamberlin, 1942:5, pi. 2, fig. 12. Hoffman, 1950a:6-7. Chamberlin and Hoffman, 1958:51. Wray, 1967:152.
Type specimens. — Male holotype (RVC), female allotype, and 1 female paratype collected by M. Winslow, 21 July 1916, from Transylvania Co., NC, along "Bennett Gap Rd.," PNF. Bennett Gap is on the HaywoodTransylvania county line about 8.6 mi. NW Brevard, but there are no roads leading to the gap today, and there is no reason to believe that there was one in 1916. US highway 276 passes through Wagon Road Gap, a few miles north of Bennett Gap, and Forest Service Rd. #475 in western Transylvania County leads off this route and parallels the county line a few miles southeast of Wagon Road Gap. Sigmoria stenogon has never been collected in Haywood County, so the locality must be on the Transylvania side of the line. Since specimens have been taken from Pink Beds Recreation Area along Forest Service Rd. 475, it seems that the type locality was probably along the road to Wagon Road Gap (US hwy. 276) rather than one to BenDiagnosis. — A moderate-size species of Sigmoria with medial flange on proximal portion of peak and with violet paranota and violet transverse stripes along caudal margins of metaterga; gonopods with following diagnostic characters: prefemoral process relatively long, thickness variable; acropodite thin and fragile, arch flattened and extending beyond level of prefemoral process; anterior bend sharp, well defined; peak long and flat; apical curve bisinuate, with two parts bending inward toward arch; tip reflexed; medial flange very long and narrow, scarcely wider than, and poorly demarcated from, stem of acropodite, arising at anterior bend, terminating at second inward bending part of apical curve; lateral flange variable but usually distinctly visible, when present ranging from subtriangular with margin broadly rounded to a long subrectangular projection arising perpendicularly from acropodite stem.
Holotype.— Length 38.9 mm, maximum width 8.9 mm, W/L ratio 23.0%, depth/width
Color in life unknown; Chamberlin's comments (1942) were based on a preserved specimen that had been in alcohol for 36 years.
Somatic features similar to /. latior, with following exceptions:
Width across genal apices 4.3 mm, interantennal isthmus 1.3 mm. Antennae short, extending back to just beyond caudal margin of 2nd tergite, relative lengths of antennomeres 2>3>5>6>4>1>7. Facial setae as follows: epicranial, interantennal, and genal absent; frontal 1-1, clypeal about 10-10, labral about 12-12.
Collum broad, extending well beyond ends of following tergite. Caudolateral corners of paranota rounded on segments 1-3, becoming progressively more acute thereafter. Peritremata slightly thickened.
Process of 4th sternum (Fig. 55) very small, much shorter than width of adjacent coxae; knobs between 4th legs and elevated flattened areas between 5th present but relatively small and inconspicuous; sternum of segment 6 not significantly depressed between 7th legs. Postgonopodal sterna generally flat, with shallow transverse grooves arising between legs. Coxae with low tubercles beginning on segment 8, becoming progressively longer and sharper caudally.
Gonopodal aperture broadly ovoid, 3.0 mm wide and 1.7 mm long at midpoint, indented along anteriolateral edge, sides flush with metazonal surface. In situ configuration of gonopods unknown, see comments under variation. Gonopod structure as follows (Figs. 57-58): prefemoral process moderately long, cuneate, subbisinuately curved, directed toward tip of acropodite. Acropodite thin and fragile, arch flattened and overhanging prefemoral process; anterior bend sharp and well defined, located at about 1/3 length; peak of arch flattened and long, about 1/3 of acropodite length; apical curve bisinuate, with broad inward bending proximal part followed by outward curving part then bending inward sharply again; distal zone relatively short, bent inward into arch; tip reflexed, directed toward midlength of basal zone. Medial flange very long and narrow, only slightly wider than, and poorly demarcated from, stem of acropodite, arising at anterior bend, terminating at beginning of second inward bending part of apical curve. Tooth absent. Lateral flange subtriangular, projecting from acropodite stem along second inward bending part of apical curve. Prostatic groove running along inner face of acropodite, crossing to lateral side at anterior bend and continuing to tip.
Female allotype. — Length 46.4 mm, maximum width 10.1 mm, W/L ratio 21.8%, depth/width ratio 70.3%. Agreeing with holotype in most somatic features, with following exceptions: paranota angled more sharply ventrad giving appearance of more highly arched body, corners rounded on segments 1-6; collum not extending beyond ends of following tergite; caudal margin of 2nd segment angled anteriad; peritermata lower and less distinct.
Cyphopods in situ with valves visible in aperture, receptacle located adjacent to legs. Receptacle subtriangular, situated dorsal to and not surrounding valves, surface finely granulate. Valves relatively large, surface finely granulate.
Variation. — Sigmoria stenogon displays the typical striped color pattern of other montane "sigmoid" xystodesmids but differs in having less of a
reddish tint to the paranota and stripes. The specimen I collected in Flat Rock, Henderson County (NCSM 2572) had purple stripes and paranota, whereas those from Bruce Falls in Transylvania County (NCSM A2054) were violet.
The in situ gonopodal configuration of the holotype is unknown, and the following description is taken from a male from Bruce Falls, Transylvania County (NCSM A2054) (Fig. 56). Each acropodite lies across the opposite side of the aperture and curves anteriad beyond the anterior edge of the aperture. The right one curves caudally behind the left, and the two do not actually overlap, although this could be accomplished with slight repositioning. The left acropodite extends farther anteriad over the 6th sternum than does the right, due to the more caudal position of the latter.
Several aspects of the gonopods vary, including the shape of the prefemoral processes, general curvatures of the acropodites, and configurations of the medial and lateral flanges. The prefemoral process is narrower and curved slightly at midlength in males from the northern part of the range near US highway 74 in Henderson County. In specimens from Hendersonville, Flat Rock, and Transylvania County, this process is thicker and similar to that of the holotype. The northern specimens exhibit a basal spur on the inner face of the acropodite just distal to the prefemur, but this spur is absent from the other males. The curvature of the acropodite varies, with the peak of the arch shorter and more curved in some individuals, resulting in less overhanging of the prefemoral process. The medial flange is always narrow but is more distinct and has a round apical lobe on the northern males. The lateral flange in Transylvania males resembles the condition in the holotype, but it varies greatly in specimens from Henderson County. The male from Flat Rock (Fig. 59) lacks the flange, whereas northern males (Fig. 60) possess a long, subrectangular projection. In these individuals the flange arises suddenly at a perpendicular angle from the acropodite, and in lateral view the gonopods appear almost chelate (Fig. 60). The margins of the flanges in these specimens are quite irregular, with several indentations and notches.