Sigmoria bidens (Causey 1942)

Sigmoria bidens (Causey)
Apheloria bidens Causey, 1942:169-170, fig. 9. Dixioria bidens: Causey, 1950:6. Wray, 1967:152. Falloria bidens: Chamberlin and Hoffman, 1958:33.
Figs. 78-81, 132-133,136
Type specimens. — Male holotype and female allotype (ANSP Type #11263) collected by N.B. Causey, 21 June 1940, from Sevier Co., TN,
Figs. 78-81, Sigmoria bidens. 78, process of 4th sternum of holotype, caudal view. 79, gonopods in situ, ventral view of topotype. 80, telopodite of left gonopod of holotype, medial view. 81, the same, lateral view. Scale line for fig. 79 = 1.00 mm; line for other figs. = 1.00 mm for each. Chimneys Picnic Area, Great Smoky Mountains National Park, along US hwy. 441, circa 7.3 mi. S Gatlinburg. According to Causey (1942) 3 female paratypes were taken at the same time and place, but their current location is unknown.
Diagnosis. — A moderate-size species of Sigmoria with medial flange on proximal portion of peak and with red paranota and usually blue transverse stripes along caudal margins of metaterga; gonopods with following diagnostic characters: prefemoral process greatly enlarged, subglobose basally, extending to or beyond level of tip of acropodite; acropodite relatively wide basally, becoming much thinner at anterior bend; anterior bend broad, poorly defined, beginning near base of acropodite; medial flange long and narrow, extending most of length of peak, poorly demarcated from stem of acropodite; tooth subconical usually widely separated from flange, located on distal zone; tip slightly reflexed, directed toward midlength of basal zone.
Holotype. — Length 41.0 mm, maximum width 9.4 mm, W/L ratio 22.9%, depth / width ratio 60.6%. Segmental widths as follows: Color in life (from Causey 1942): paranota bright red; metaterga dark brown; head and antennae lighter brown; distal half of legs red; venter and proximal half of legs pale yellow. This notation was obviously taken from faded, preserved material, and Causey did not mention metatergal stripes in her description.
Somatic features similar to /. latior, with following exceptions:
Width across genal apices 5.0 mm, interantennal isthmus 1.9 mm. Antennae long and slender, reaching back to caudal edge of 3rd metatergum, relative lengths of antennomeres 2 = 6>3 = 5>4>1>7. Facial setae as follows : epicranial , interantennal , frontal , and genal not detected; clypeal about 10-10, labral about 8-8.
Collum not extending beyond ends of following tergite. Paranota depressed, continuing slope of dorsum, caudolateral corners rounded on segments 1-5, squared on 6-13, and becoming progressively more pointed posteriorly. Peritremata distinct on segments 4-18 but only slightly elevated above paranotal surface.
Process of 4th sternum moderate in size (Fig. 78), subequal in length to width of adjacent coxae; knobs and elevated areas of 5th sternum moderate in size; sternum of segment 6 convexly recessed between 7th legs to accommodate curvature of telopodites. Postgonopodal sterna generally flat and unmodified, bicruciately impressed on segments 8-9 and with shallow, rounded, central impressions on 10-16. Coxae with low blunt tubercles on legs of segments 11-17.
Gonopodal aperture relatively large and ovoid, 3.9 mm wide and 2.0 mm long at midpoint, indented slightly along anteriolateral edge, margins slightly elevated above metazonal surface. Gonopods in situ (Fig. 79, of topotype) with acropodites overlapping at about midlength in midline of aperture and again at region of apical curve, extending forward over anterior edge of aperture to between 7th legs. Gonopod structure as follows (Figs. 80-81): prefemoral pro
cess greatly enlarged, extending to level of tip of acropodite, subglobose basally, bifurcate apically, components acuminate and subequal in length but lateral one wider. Acropodite relatively wide basally, becoming thin and narrow distal to anterior bend, arch extending beyond and overhanging prefemoral process; anterior bend relatively broad and poorly defined, beginning near base of acropodite; peak of arch relatively long and flattened but gradually rising to apex at beginning of apical curve; apical curve relatively broad and poorly defined, forming arc with relatively broad diameter; distal zone moderate in length, broadly curving inward into arch; tip slightly reflexed, projecting inward from distal zone, directed toward midlength of basal zone. Medial flange relatively long and narrow, poorly demarcated from stem of acropodite, arising near base of anterior bend and terminating at start of apical curve, obscuring only small section of stem of acropodite. Tooth present, acuminate and subconical, displaced distad and clearly separated from medial flange, located at about 1/3 length of distal zone. Lateral flange long and narrow, beginning at apical curve and terminating just proximal to tip. Prostatic groove running along inner face of acropodite basally, crossing to lateral side at anterior bend and continuing to tip.
Male topotypes. — The topotypes that I collected at Chimneys Picnic Area (NCSM A 1888) had red paranota with wide, blue, transverse connecting stripes along the caudal margins of the metaterga and both the anterior and caudal margins of the collum. The blue stripes in this sample were distinct and quite different from the black metatergal base color.
The males in this sample are somewhat variable in size, some being much smaller in length and width than the holotype.
The gonopods of these males differ slightly from those of the holotype in the configuration of the prefemoral process and medial flange. The former structures tend to be less globose basally and more distinctly bifurcate apically, although the bifurcation is not always visible in medial view. The medial flange is much narrower than that of the holotype and is only slightly wider than the acropodite stem.
Female allotype. — Length 42.7 mm, maximum width 10.3 mm, W/L ratio 24.1%, depth/width ratio 69.9%. Agreeing essentially with males in somatic features except paranota more strongly depressed creating impression of more highly arched body.
Cyphopods in situ with receptacle visible in aperture, valves directed caudolaterad. Receptacle cupped around ventral end of valves, extending slightly down both sides, surface with deep grooves and folds. Valves moderately large, surface mildly grooved.
Variation. — The color of bidens varies; specimens from along US highway 441, 1.3 mi. E Chimneys Picnic Area (NCSM A1903) had red paranota and red stripes, whereas those from the Elkmont Campground area (NCSM A 1936) had pink peritremata, but the rest of the paranota and the stripes were dark purple. All other specimens were the same colors as the topotypes.
The most significant gonopodal variation involves the prefemoral process. The structure is always much larger basally, but it is irregularly shaped rather than subglobose on some specimens. The apical bifurcation also changes, and the medial component is longer on some males. Individuals from near Elkmont campground possess the longest prefemoral processes, as the longer medial components extend beyond the level of the tip of the acropodites. Other gonopodal variation includes the length of the peak of the arch and the general curvature of the acropodite. The peak is typically flat, so that the structure overhangs and extends well beyond the level of the prefemoral process. The male from Gatlinburg (FSCA), however, is more highly arched with a relatively short peak, and consequently the acropodite barely extends beyond the prefemoral process.