Remenus Ricker, 1952

Verdone, Chris J. & Kondratieff, Boris C., 2018, Holomorphology And Systematics Of The Eastern Nearctic Stonefly Genus Remenus Ricker (Plecoptera: Perlodidae), Illiesia 14 (5), pp. 81-125 : 89-92

Genus Remenus Ricker, 1952

( Figs. 1 , 3–18 )

Type species: Perla bilobata Needham & Claassen (1925: 95)

Isogenus (Remenus ) Ricker (1952: 122)

Remenus: Illies (1966: 376)

Remenus: Hitchcock (1974: 214)

Remenus: Stewart & Stark (1984: 406)

Remenus: Stewart & Stark (1988: 402)

Remenus: Kondratieff & Nelson (1995: 596)

Remenus: Stewart & Stark (2002: 437)

Remenus: Kondratieff (2004: 164)

Remenus: Stark (2017: 236)

Male. Macropterous; forewing length 9.1–11.0 mm (n = 40). Body length 7.9–10.6 mm (n = 40). General body color yellow-gold with light brown markings Fig. 1 ). Head as wide as, or wider than pronotum; crossveins ( Fig. 4 ). Y-arms of mesosternum meeting posterior corners of furcal pits. Femora pale, light brown dorsally. Tibia pale, light brown dorsally. Tarsi light brown. Abdominal sterna pale to yellowgold; lobe on 7 th sternum well developed, lightly pigmented, narrowly rounded, apex rounded ( Fig. 5 ); lobe on 8 th sternum reduced, ~ ⅓ the size of lobe on sternum 7, triangular, lightly pigmented, apex acutely rounded ( Fig. 5 ). Abdominal terga usually yellow-gold, with variable color pattern, covered in regularly spaced with setae; terga 8 and 9 with variable patches of sensilla basiconica ( Fig. 6 ). Hemitergal lobes variously produced with long trichoid sensilla and various densities of sensilla basiconica ( Fig. 6 ). Cerci pale, setose ( Figs. 5–6 ). Lateral stylets absent. Epiproct variable, small, mostly membranous; with or without a mediodorsal sclerite ( Fig. 7 ). Membranous portion covered in dense, minute hair-like spinulae. Paragenital plates flap-like, triangular or rounded ( Figs. 6–7 ). Basal cowl clothed in dense variably pigmented spinulae ( Fig. 7 ). Aedeagus entirely membranous with two lateral and two posterodorsal lobes ( Figs. 5–7 ).

Female. Macropterous; forewing length 9.4–12.0 mm (n = 40). Body length 8.8–12.6 mm (n = 40). General body coloration similar to male. Abdominal terga and sterna generally uniformly pale yellow. Subgenital plate broadly rounded or broadly triangular, produced over ½ sternum 9, or beyond ( Fig. 8 ); with regularly spaced setae; a variable glabrous basolateral crease is present at the base of the subgenital plate and extends anteriorly up to ⅓ into tergum 8 ( Fig. 8 ).

Ovum. Length 434–460 μm; width 324–361 μm (n = 12). Turtle-shaped with a ventrally positioned collar ( Fig. 9 ). Mature ovum with a membranous covering, adorned with regularly spaced globules in clusters of 2–5 ( Fig. 9 ). Dorsum of chorion smooth with very faint diamond-shaped follicle cell impressions. Dorsal keel extending from collar center to ovum center ( Fig. 9 ). Collar with prominent diamondshaped follicle cell impressions dorsally and ventrally ( Figs. 9–10 ). Ovum margin with a thickened raised edge. Micropyles positioned ventrally; arranged in a latitudinal row of 6 near the collar ⅓ ( Fig. 10 ).

Larva. Body length 8.3–11.4 mm, (n = 19). Preserved specimen yellow-brown. Head wider than pronotum ( Fig. 11 ); dorsum of head yellow- brown; frons with a faint, thin, pale M-shaped mark ( Fig. 11 ); pale enclosed oval spots anterolateral of lateral ocelli, anterior of epicranial suture ( Fig 11 ); large enclosed oval spots posterolateral of lateral ocelli, posterior of epicranial suture (Fig, 11); 2–4 postocular setae ( Fig. 11 ); frontoclypeus unpigmented; labrum anterior margin with a setal fringe ( Fig. 11 ); medial lobe of labrum with a dense fringe of golden setae. Lacinia unidentate ( Fig. 12 ); lacinia sickle-shaped, tapering evenly from apical tooth and bearing stout, rounded, basal knob ( Fig. 12 ); apical tooth with ~ 12 minute irregularly spaced setae extending halfway up the lacinia from the inner basal surface across the dorsal surface to the distal margin ( Fig. 12 ). Basal knob with 5–6 submarginal minute setae ( Fig. 12 ). Mandible with 5 teeth and without a deep cleft between the apical and subapical teeth ( Fig. 13 ). Middle three teeth with proximal margins lightly serrated; dorsum of mandibles with a dense patch of stout setae ( Fig. 13 ); proximal margin with a dense brush of stout setae on apical ⅓ ( Fig. 13 ). Maxillary palp slightly longer than lacinia ( Fig. 14 ). Submental gills absent ( Fig. 14 ). Pronotum yellow-brown; 10–16 long erect marginal setae on each side; lateral margins of pronotum brown ( Fig. 11 ). Meso- and metanota yellow-brown; with 0–1 seta on either side of midline; 1–6 anterolateral setae ( Fig. 15 ); wing pads with 1–7 marginal setae on proximal margin ( Fig. 15 ). Y-arms of mesosternum reach the posterior corners of furcal pits. Femora pale yellow-brown with long stout setae over surface and without a dorsal fringe of silky setae. Tibia with short stout submarginal setae on dorsal and ventral surfaces and a dorsal fringe of silky setae. Tarsi with a short dorsal fringe of silky setae. Abdominal terga yellow-brown, with a posterior fringe of variable length setae ( Fig. 16 ); longest setae ~ ⅔ length of tergum; terga 1–2 without intercalary setae ( Fig. 16 ); terga 4-10 with <35 intercalary setae ( Fig. 16 ). Abdominal sterna pale yellow-brown; sterna 1–2 without a posterior fringe or intercalary setae; sternum 3 occasionally with a single posterior seta laterally; sterna 4–8 with <35 intercalary setae and a posterior fringe of variable length setae that is interrupted medially ( Fig. 17 ); highest concentration of intercalary setae on abdominal segments 7–9 ( Figs. 16–17 ); female 8 th sternum with a thin darkened strip posteromedially ( Fig. 17 ); posterior fringe complete on sterna 9–10 ( Fig. 17 ). Mature male larvae with an elongate terminal process (developing epiproct) with a constriction at the basal ⅓, apical ⅔ thin and tapered ( Fig. 18 ). Mature larvae with paired medial and lateral spots on the abdominal terga. Cerci with whorls of short or long setae, or a combination of both ( Figs. 16, 18 ).

Diagnosis. Regionally, Remenus is morphologically most similar to Diploperla duplicata (Banks, 1920) . The two are often sympatric and share the following characters: (1) male tenth tergum partially cleft; (2) lobe on 7 th sternum well developed, narrowly rounded, and lobe on 8 th sternum reduced, ~ ⅓ the size of lobe on 7 th sternum; (3) female subgenital plate broadly rounded with a membranous basolateral crease; (4) interocellular area enclosed with medium brown pigment that generally narrows towards the anterior ocellus and extends laterally from anterior ocellus to center of lateral ocelli; (5) larvae and adults lack submental gills; (6) larvae are similarly concolorous; (7) larvae have a dorsal fringe of setae on the tibia and lack a fringe on the femora; and (8) ova are turtle shaped.

Adult males of Remenus are distinguished from D. duplicata by the presence of a well-developed epiproct and the lack of lateral stylets. Adult females of Remenus differ by the presence of distinct mesosternal Y-arms and <3 cross veins in the apical costal space. Whereas D. duplicata has> 5 cross veins in the apical costal space. Larvae of Remenus are easily distinguished from D. duplicata by their unidentate lacinia and well-developed mesosternal Y-arms. Ova of Remenus are also easily separated by their relatively smooth chorionic surface and the diamond-shaped follicle cell impression on the collar.

Figures

Fig. 1. Remenus kirchneri, spring fed stream, Blue Ridge Parkway, east of Mt. Olivet Church, Floyd County, Virginia.

Figs. 3–6. Remenus bilobatus, adult male. 3. Head and pronotum, AO = anterior ocellus, AS = antennal scape, ES = epicranial suture, Fr = frons, IoA = interocellular area, LO = lateral ocelli, MPA = medial pale area, Ro = rugosities, Th1 = pronotum. 4. Right forewing, A = anal vein, ACS, apical costal space, C = Costal vein, Cu = cubital vein, M = median vein, R = radial vein, Rs = radial sector vein, Sc = subcostal vein. 5. Male abdominal sterna 7–10, A = posterodorsal lobes, Ae = aedeagus, Ab = abdominal segment, B = lateral lobes, SL = sternal lobe. 6. Male abdominal terga 8–10, A = posterodorsal lobes, Ae = aedeagus, Ab = abdominal segment, B = lateral lobes, BA = basal anchor, HL = hemitergal lobe, PP = paragenital plate, SB = sensilla basiconica.

Figs. 7–10. Remenus bilobatus adult and ovum. 7. Male terminalia, lateral, A = posterodorsal lobes, Ae = aedeagus, Ab = abdominal segment, B = lateral lobes, Co = Cowl, DS = dorsal sclerite, Ep = epiproct, HL = hemitergal lobe, PP = paragenital plate. 8. Female abdominal sterna 8–10, Ab = abdominal segment, BC = basolateral crease, SP = subgenital plate. 9. Ovum, dorsal, A = globules, B = diamond-shaped follicle cell impressions, C = collar, D = dorsal keel. 10. Ovum, ventral, A = Collar, B = diamond-shaped follicle cell impressions, C = micropyles.

Figs. 11–14. Remenus bilobatus, larva, 11. Head and pronotum, A = pale M-shaped mark, B = pale enclosed anterolateral oval spot, C = postocular setae, D = large enclosed posterolateral oval spot, E = long erect marginal setae, ES = epicranial suture, Lb = labrum, Mp = maxillary palp, Th1 = pronotum. 12. Left lacinia, dorsal, A = minute irregularly spaced setae, B = minute submarginal setae, BK = basal knob. 13. Left mandible, dorsal, A = Middle three teeth with proximal margins lightly serrated. 14. Head, ventral, Gl = glossa, La = lacinia, Lb = labrum, LP = labial palp, Ma = mandible, MP = maxillary palp, Pg = paraglossa, PM = prementum.

Figs. 15–18. Remenus bilobatus, larva. 15. Meso- Meta-nota, A = mesonotal anterolateral setae, B = metanotal anterolateral setae, C = mediolateral seta, D = marginal setae, Th2 = mesonotum, Th3 = metanotum. 16. Male abdominal terga 6–10, A = posterior setal fringe, Ab = abdominal segment, B = intercalary setae, C = basal cercal segments, Ep = male terminal process (developing epiproct). 17. Female sterna 7–10, A = posterior setal fringe, Ab = abdominal segment, B = darkened posteromedially strip, C = intercalary setae. 18. Male sterna 8–10, A = basal cercal segments, Ab = abdominal segment, B = intersegmental setae, C = intersegmental setae, Ep = male terminal process (developing epiproct).