Rhyacophila sociata Navas 1916, status resurrectus
Creators: name: Valladolid, María
name: Arauzo, Mercedes
name: Basaguren, Ana
name: Dorda, Beatriz A.
name: Rey, Isabel
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Trichoptera
Rhyacophilidae
Rhyacophila
Rhyacophila sociata

description: Rhyacophila sociata Navás 1916 (status resurrectus).
In his publication, NavÁs (1916) described one male collected in Solares (Cantabria), and as stated previously, Schmid (1949) did not included it in his study of NavÁs’ collection. A staff person of the University of Zaragoza, where the insect collection of NavÁs was housed years ago, suggested that the holotypes, including that of R. sociata, possibly were sent to the Museo de Ciencias Naturales of Barcelona. The curator of the arthropod collection of this museum informed us that this specimen is not in the Barcelona collection, nor is the specimen described as R. gemella (NavÁs 1923). Consequently, we decided to designate a neotype for this species.
In a second step, we tried to collect new specimens from Solares, without success, and researchers working in this area confirmed that they never collected the species there. We decided to designate also a new type locality, where the neotype specimen was captured.
Neotype: 1 male (08/06/09). Collection number: MNCN _ Ent 160675. Tissues and DNA Collection Number: MNCN / ADN 57444.
Other specimens: 3♂, 30/06/08; 1♂ + 6♀, 06/08/08; 1♂ + 1♀, 08/06/09; 1♂, 3/07/09. Collection numbers, see Table 1.
Type locality: Casalarreina, La Rioja (Spain). River Oja. Latitudinal and longitudinal geographic coordinates: 42.546105 N, 2.915515 W. Altitude: 490 m a.s.l.
Description of the larva. Biometrics last instar larva and prepupa: Length: 9.43–15.34 mm (x̅ = 2.28, n = 26). Maximum width of larva at metathorax. Maximum width of abdominal segments II–III: 2.32–4.13 mm (x̅ = 2.96, n = 26).
Color: Thorax and abdomen greenish, dorsum with dark areas delimited by narrow, pale, dorsolateral marks. Sclerotized areas of head and thorax dark brown with pale spots and stripes. Specimens preserved in alcohol generally pale yellow, with sclerotized areas reddish brown to black in some places.
Head (Fig. 1). Length: 1.37–2.23 mm (x̅= 1.58, n = 26). Width: 1.00–1.84 mm (x̅= 1.22, n = 26). Maximum width in posterior third of head, approximately in line with sensory pits #9. Cephalic capsule (Figs 1a, 1b), in dorsal view with yellow background anterior of setae #6 and light brown posterior of them, across full width of dorsal view (Figs. 1a, 1b) and halfway down sides (Fig. 1c), except sometimes lighter posterior occiput and beside frontoclypeal and coronal sutures. Ventral view uniformly yellow, without dark spots. Frontoclypeal apotome (Fig. 1d) with brown pattern in posterior third, posterior of setae #6, this pattern U–shaped in 59% of specimens studied (modified U–shape in 41% of specimens), and with 3–4 pale muscle attachment spots with dark borders inside pattern. Posterior dorsal area of head with pair of brown patches, marked with darker muscle attachment spots (in 78% of specimens). Three light spots around setae #15, #16 and #19–21, forming pair of light longitudinal stripes along head in 53% of specimens. Light triangular spot on juncture of frontal and coronal sutures in 85% of specimens, sometimes replaced by pair of light spots around sensory pits #9. On posterior occipital zone, pair of light areas connecting with dorsal light stripes of setae #15, #16 and #19–21 in 61% of specimens. Most specimens (73%) with light areas bordering frontal and coronal sutures (n = 100).
Mandibles (Fig. 2) asymmetrical, as in other rhyacophilids, left one bigger than right one. Inner blade of left mandible smooth, convex, right mandible with small tooth in middle. Maxillolabium and labrum (Fig. 3) as in other Rhyacophila species. Mentum rectangular (Fig. 3a), its anterior half slightly sclerotized. Labrum (Fig. 3b) with small transparent area in middle of anterior edge.
Thorax (Fig. 4): Anterior half of pronotum pale or very light coloured in 88% of specimens studied. Sinuous posterior margin bordered by dark band, black in middle and posterolaterally, light brown submesally. Posterior half of pronotum (Fig. 4a) with three dark triangular areas separated by light zones, central dark region tapered posteriorly and reaching posterior edge of sclerite, its anterior reaching sensory pit #P2. Lateral dark triangular areas separated from posterior margins by light stripes, each delimited by line of small darker points parallel to back edge. Each pronotal plate with curved row of dark dots from anterior edge of lateral dark triangular area toward anterolateral corner, curving around circular spot on anterior half of most pigmented specimens (Fig. 4a). Circle of dark dots also around setae #5. Anterolateral margin of each pronotal sclerite black only in anterolateral angle and extending posterad laterally without contacting posterolateral margin (Fig. 4b). Anterior margin not coloured, sometimes with small, brown spot near anterior angle. Central area of posterior marginal band of each sclerite light brown, not black (Fig. 4b).
Abdomen (Figs. 5–7): Similar to other species of Rhyacophila. Colour as for meso- and metathoracic segments, greenish with dark dorsal areas delimited by light bars in living larvae and light reddish brown dorsally and pale yellow ventrally in fixed larvae. Widths of anterior abdominal segments similar, narrower in posterior segments. Lateral abdominal gills in tufts of 21–25 filaments. Dorsal sclerite of the segment IX (Fig. 5) light coloured, with two narrow discontinuous black bands on anterior and posterior edges. Anal prolegs (Figs. 6D, 6V, 7a) typical of group, with long sword process (Figs. 7a, 7c). In this aspect, R. denticulata differing from R. sociata in that, instead of this long sword process, basilateral plate with short and angular process (Despax 1928a, fig. 6). Anal claws each with two–three teeth on ventral edge (Figs. 7a, 7b), basoventral hook black basally and reddish brown apically (Figs. 6V, 7c).
Legs (Fig. 8): Similar to those of other Rhyacophila species. With light reddish brown colour, dorsoproximal coxa black, with small black areas also in dorsoproximal femur and proximal trochanter (dorsal and ventral). Light- coloured zone in distal dorsolateral area of tibia of each of three pairs of legs. Forelegs each with spicules, extending ventrally from distal part of trochanter to end of tarsus, with different disposition on each segment: On trochanter forming isolated tufts, on femur forming double rows, on tibia tufts ventrally and in rows laterally and on tarsus, similar to trochanter but with tufts more densely distributed. Setae reddish, some thicker and darker: On each foreleg, setae 1,3,4 of coxa and 1,4 of trochanter and 1,2,4,6 of femur; on each midleg, setae 1,4 of coxa and trochanter and 1,2,4,6 of femur; on each hindleg, setae 1,4,5 of coxa and 1,4 of trochanter and 1,2,3,4,6 of femur.
Description of the pupa. Biometrics of pupa and cocoon. Pupal length (total): 8.24–14.08 mm (x̅= 10.83, n = 39); male pupa: 8.24–11.45 mm (x= ¯ 9.72, n = 19); female pupa: 8.36–14.08 mm (x¯ = 11.08, n = 20). Maximum width of young pupa in abdominal segments II and III. Cocoon length (total): 11.00– 15.50 mm (x= ¯ 13.32, n = 32); width: 3.00– 4.64 mm (x¯ = 3.67 mm, n = 32); male cocoon length: 11.00– 14.28 mm (x¯ = 12.68, n = 15), width: 3.18–4.05 mm (x¯ = 3.55 mm, n = 15); female cocoon length: 11.58–15.30 mm (x¯ = 13.89, n = 13), width: 3.00–4.37 mm (x̅= 3.77, n = 13).
Head: Distribution of setae on dorsal head similar to that of R. denticulata (Despax 1928a). Mandibles similar in R. denticulata and R. sociata, left one with two large teeth and right one with three, with numerous fine teeth on inner blade. Labrum similar in shape to that of R. denticulata. Antennae in R. sociata of variable length, reaching from middle of abdominal segment V to anterior part of segment VII.
Thorax: Tubercules of prothorax each with 5–6 setae in R. sociata but only 4 in R. denticulata. Wing pads reaching posterior edge of abdominal segment IV in R. sociata, and posterior edge of segment III in R. denticulata (Despax 1928a).
Abdomen: Paired hook plates of anterior margins pedunculated and present from abdominal segments IV to VII; anterior hook plates on abdominal segment III not visible in R. sociata (Fig. 9), small and with 3–4 spines developed and 3–4 very small in R. denticulata (Despax 1928a). Paired posterior hook plates sessile and on segments III–V in the two species. Number of hooks per plates varying among these species, being least numerous in R. denticulata (see Despax 1928a), and of intermediate abundance in R. sociata (Fig. 9).
Description of the imago. Males length: 9.50–10.80 mm (x̅= 10.07, n = 7), each forewing: 10.8–11.8 (x̅= 11.29, n = 7), each hind wing: 9.30–10.40 mm (x= ¯ 9.83, n = 7); females, length: 10.70–12.60 mm (x= ¯ 11.54, n = 7), each forewing: 11.80–12.80 mm (x̅ = 12.36, n = 7), each hind wing: 10.70–11.10 mm (x̅= 10.96, n = 7).
Colour generally pale, yellowish with setae reddish brown. Head and thorax reddish brown, abdomen yellowish, with small black spots in dorsal and lateral areas, sometimes also with dark bands on each side of abdominal segments IV–V to VII. Legs light, with spurs reddish brown. Wings pale, darker in females. Dark area on leading edge, between subcostal (Sc) and radial 1 (R1) veins in forewing and between Sc and radial 2 (R2) in hind wing; in R. fasciata this area present between Sc and R1 in both wings, but in R. denticulata only in forewing, between Sc and R2 together with dark spots in edge of wing, at R1–R5 and medial 1 (M1) veins.
Male genitalia (Figs. 10, 11): 2nd segment of each inferior appendage quadrangular, with basal and distal edges nearly parallel, posterior and ventral edges slightly concave. Apicodorsal and especially apicoventral angles rounded, apicoventral angle projecting as lobe narrowing progressively to apex. In R. denticulata and R. fasciata males, 2nd segment of each inferior appendage wider basally than in R. sociata, with basal and distal edges diverging, apicodorsal vertex more angular and ventral lobe thicker; also posterior edge sinuous in these two species, in R. denticulata concave in the upper and lower halves, concavities less conspicuous in R. fasciata (Fig. 10A).
Parameres (Figs. 10B, 11) each in lateral view slender at base, dilated in middle, with rounded dorsal and ventral margin, and pointed at apex, with few thick spines on midventral margin and small spicules or chaetae on posterior half of external surface. In dorsal and ventral views parameres curved posteromesad in apical 1/3. In R. denticulata parameres more dilated than in R. sociata, each with midventral and lower half of midlateral areas covered with spines long and thick on ventral margin and decreasing in size dorsally, middorsal half with small spines or chaetae; parameres more strongly curved posteromesad in apical 1/3, apex often sinuous and/or overlapping. In R. fasciata, parameres in lateral view each with base slightly thicker than for other two species and less dilated in middle, midlateral surface almost covered with spines, thicker spines on ventral margin, decreasing in size dorsally, spines of ventral margin less numerous than in R. denticulata; slightly curved posteromesad in apical 1/3 and often overlapping apically (Figs. 10B, 11).
Aedeagus (phallicata) in lateral view (Fig. 10 CL) slender and clearly curved in middle, with mid-dorsal margin concave and midventral margin convex, apically with margins almost parallel. Ventral lobe of phallus with parallel margins basally in dorsal view, abruptly narrower apically, apicolateral margins rounded, aedeagus apically blunt (Fig. 10 CV). Aedeagus of R. denticulata in lateral view with mid-dosal margin concave for short distance but midventral margin not convex, ventral lobe in dorsal view with margins convex and narrowing progressively toward apex, apicolateral margins slightly projecting caudad, and aedeagus slightly pointed (Fig. 10 CV). Aedeagus of R. fasciata in lateral view with mid-dorsal margin concave and posterior corner of concavity hooked anterad, midventral margin with small notch, in dorsal view margins of ventral lobe similar and aedeagus similar to R. sociata (Fig. 10 CV).
Apicodorsal lobe of segment IX dilated subapicolaterally, with small apicomesal excision; preanal appendages shorter than that lobe, with round edges and small invagination near contact area between segment IX and preanal appendages (Fig. 10 DD). In ventral view, apical band V-shaped, anal sclerites triangular (Fig. 10 DV). In R. denticulata apicodorsal lobe of segment IX dilated subapicolaterally about as much as for R. sociata, but with apex rounded and without excision, preanal appendages shorter than that lobe, more nearly squared than in R. sociata, in ventral view, apical band U-shaped, anal sclerites triangular. In R. fasciata, apicodorsal lobe more dilated than in R. sociata and R. denticulata, almost from its base, and with broad apicomesal excision, similar to R. sociata. In ventral view, apical band V-shaped, with apices close together, anal sclerites triangular (Fig. 10 DV).
Female genitalia (Fig. 12): In lateral view, segment VIII valves of R. sociata with posterior margin shallowly concave apically, with each dorsolateral apex extending farther posterad than ventrolateral apex. In R. denticulata, posterior margin with two small projections on each side, one dorsal and one ventral separated by modest indentation and ventrolateral apex longer than dorsolateral apex. In R. fasciata posterolateal margin on each side triangular and longer than small dorsolateral projection, excision between them corresponding to shallow posterior concavity of R. sociata and dorsolateral indentation of R. denticulata.
In dorsal view, R. sociata with indentation between broad segment VIII valves, apicodorsal ends of valves with rounded apical and subapical corners and delimiting subcircular space. Rhyacophila denticulata also with apicodorsal ends of valves broad but with apical and subapical corners more nearly rectilinear than in R. sociata and delimiting transversely oval space. In R. fasciata apicodorsal ends of segment VIII valves small, blunt, with delimited space more nearly triangular, wider anteriorly.
In ventral view, R. sociata with segment VIII valves forming two elongated sclerites, fused basally, intersegmental membrane with pair of dark sclerites united anteriorly to form heart-shape structure. In R. denticulata, segment VIII valves not united basally, two intersegmental membrane sclerites coma-shaped, not fused, thicker in anterior 1/3 and more widely separated posteriorly. In R. fasciata, segment VIII valves widely separated and not fused basally, intersegmental membrane sclerites longitudinally oval and more widely separated than in R. denticulata.
Genetic analysis. The first approximations at the genetic level for the European samples of R. fasciata, R. denticulata, and R. sociata showed that R. fasciata samples could be separated into at least two different groups: One group of specimens from Austria and a second one from central-northern Europe. The difference was sufficient to considerer these groups to represent at least two species. A study of these two species will be conducted in the future. Since the original description of R. fasciata was based in specimens from Carinthia (Austria), we used the sequences from Austria for the comparison with R. denticulata and R. sociata.
The mitochondrial sequences analyzed show clear differences between the R. fasciata specimens from Austria and those of R. denticulata and R. sociata. Based on the divergence of sequences, there are two differentiated branches, one corresponding to R. fasciata and another that includes R. sociata and R. denticulata species (Fig. 13). The specific clades are supported by very high bootstrap values in the three cases (98 for R. fasciata, and 99 for the R. sociata – R. denticulata node and for each of the R. sociata and R. denticulata branches). The genetic distances (maximum composite likelihood model) between the species, including an outgroup species (R. relicta McLachlan 1879), were 0.041 (R. sociata – R. denticulata), 0.052 (R. sociata – R. fasciata) and 0.056 (R. denticulata – R. fasciata). The pairwise distances between each of these species and the outgroup were 0.076 (R. relicta – R. fasciata), 0.095 (R. relicta-R. sociata), and 0.103 (R. relicta – R. denticulata). The maximum intraspecific distances obtained were 0.0062 for R. sociata, 0.0053 for R. denticulata, and 0.0040 for R. fasciata.
description: Published as part of Valladolid, María, Arauzo, Mercedes, Basaguren, Ana, Dorda, Beatriz A. & Rey, Isabel, 2018, The Rhyacophila fasciata Group in Western Europe: Confirmation of Rhyacophila denticulata McLachlan 1879 (stat. prom.) and Rhyacophila sociata Navás 1916 (stat. res.), based on morphological and molecular genetic evidence (Trichoptera: Rhyacophilidae), pp. 526-544 in Zootaxa 4418 (6) on pages 530-534, DOI: 10.11646/zootaxa.4418.6.2, http://zenodo.org/record/1245456