Sierracapnia, Bottorff & Baumann, 2015

Bottorff, Richard L. & Baumann, Richard W., 2015, Sierracapnia, A New Genus Of Capniidae (Plecoptera) From Western North America, Illiesia 11 (9), pp. 104-125: 105-108

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Sierracapnia   , new genus

Type Species. Sierracapnia barberi (Claassen 1924)   .

Adults. Body length 5-7 mm; color dark brown to black; wings macropterous, forewing R1 vein curved forward near origin of RS vein and A 1 curved beyond crossvein a; cerci long, 14-18 segments. Ventral sclerites of adult thorax identical to those reported for Arsapnia   and Capnia   s. s. ( Table 1 in View Table 1 Murányi et al. 2014). Drumming signals unknown.

Male. Median knobs absent on terga 1-6; large median raised knob present on tergum 7; median knob absent on tergum 8; pair of smaller raised knobs present on tergum 9, located on each side of epiproct apex; tergal knobs densely covered with rounded tubercles of conical sensilla. Epiproct a single sclerotized member, elongated and laterally compressed, with a curved ventral keel (deep or shallow) positioned between tergum 9 knobs; pair of dorsolateral horns pointing anteriorly and with slightly divergent tips. Epiproct basal sclerite present (small to large) and fused to main epiproct sclerite; laterobasal sclerites large and fused to main epiproct sclerite. Epiproct base with a narrow or thick neck in lateral view. Epiproct apex thin, rounded, or wedge-shaped in dorsal view. Epiproct glabrous, except caudal setae present. Anterior half of epiproct surface covered with numerous shallow sensory pits, each with a small pointed projection in the center; sensory pits less abundant or absent from epiproct neck and base. Epiproct dorsal membrane extends longitudinally for more than one-half epiproct length; membrane linearly folded and with anterior eversible crest that expands or contracts in size. Subgenital plate broadly fused with sternum and tergum 9 (see Fig. 35 View Figs in Murányi et al. 2014 for definition of terms). Ventral vesicle absent. Fusion plate ( Hanson 1946) a long narrow internal structure largely hidden behind broad triangular paraprocts that are covered with stout hairs or spines, fusion plate apex exposed with a small tubular opening that fits into epiproct base, retractoral plate a thin sclerite separated from fusion plate ( Figs. 4 View Fig , 12 View Figs , 32 View Figs , and see Figs. 23 -31 View Figs View Figs in Murányi et al. 2014).

Female. Subgenital plate large and heavily sclerotized, covering all of sternum 8 and posterior margin of sternum 7; division line between sterna 7 and 8 not always obvious; posterior margin of plate broadly truncated at posterior edge of sternum 8, plate not projecting onto sternum 9. Dorsum of abdominal segments 1-8 with median membranous band; posterior margin of segment 8 with small median V-shaped sclerite.

Larva. Unknown.

Diagnosis. Murányi et al. (2014) provided a diagnosis of Capnia   s. s. Pictet 1841 and concluded that eight species, primarily from the Palaearctic, were included in this restricted concept of the genus. Capnia nearctica Banks 1919   , the only Holarctic species, has a distribution in North America that includes Alaska and northwestern Canada ( Nelson and Baumann 1989, Stewart and Oswood 2006, DeWalt et al. 2015).

Males of Sierracapnia   differ from Capnia   s. s. by their epiproct and knobs on tergum 9. Sierracapnia   males have an undivided epiproct with distinct dorsolateral horns and prominent knobs on tergum 9. Capnia   s. s. males have an epiproct divided into upper and lower members, but lack dorsolateral epiproct horns and knobs on tergum 9. In addition, Sierracapnia   males have a basal sclerite and large laterobasal sclerites fused to the main epiproct sclerite, whereas in Capnia   s. s. the basal sclerite is vestigial and the laterobasal sclerites are divided from the main epiproct sclerite ( Murányi et al. 2014). The retractoral plate is separated from the fusion plate in Sierracapnia   males, but the retractoral plate is fused to the fusion plate in Capnia   s. s. males. The subgenital plate of Sierracapnia   female adults is broad, heavily sclerotized, and extends from sternum 8 to the posterior half of sternum 7, whereas in species of Capnia   s. s. this plate is small and does not extend onto sternum 7.

Sierracapnia   and Arsapnia   adults also differ. The glabrous epiproct of Sierracapnia   males is laterally compressed and the ventral surface is most often deeply curved (less deeply curved in S. palomar   ), while for Arsapnia   males the epiproct has a narrow apical tip, laterally expanded bulb-like midsection (often with a row of stiff setae or spines), narrowed posterior neck, and straight ventral surface (Figs. 209-210 in Nelson and Baumann 1989). The epiproct of Sierracapnia   males has a basal sclerite, but this sclerite is lacking or vestigial for Arsapnia   males ( Murányi et al. 2014). The dorsolateral horns of Sierracapnia   are prominent, long structures that originate near mid-epiproct and project or arch forward about 15-30% of epiproct length. In contrast, the dorsolateral epiproct projections of Arsapnia   are small, closely appressed to the main body, and confined to the anterior quarter. The dorsal epiproct membrane of Sierracapnia   is often clearly exposed for over one-half of the epiproct length and the apex forms an eversible crest of linearly folded tissue that expands and contracts in size. In contrast, the epiproct dorsal membrane of Arsapnia   is confined to a small, narrow area near the tip and the large eversible crest is absent. Sierracapnia   males have well-developed knobs on tergum 9, with prominent rounded conical sensilla. These knobs are lacking on most species of Arsapnia   , but tiny processes are present on three species: A. pileata (Jewett 1966)   , A. teresa (Claassen 1924)   , and A. utahensis (Gaufin and Jewett 1962)   . Sierracapnia   female adults have a broad, heavily sclerotized subgenital plate that extends onto the posterior margin of sternum 7, while this plate is small and does not extend onto sternum 7 in Arsapnia   females.

Both S. palomar   and Arsapnia arapahoe ( Nelson and Kondratieff 1988)   have linear or fusiform epiprocts that differ from the typical forms found in all other species of both genera. Yet each species has characters that are most similar with their respective genus. That is, S. palomar   has a laterally compressed, glabrous epiproct with shallow ventral keel, a large basal sclerite fused to the epiproct, and a median dorsal groove that extends the full epiproct length ( Figs. 13-15 View Figs ). In addition, median knobs are present on terga 7 and 9. In contrast, A. arapahoe   has a slightly recurved epiproct that lacks a ventral keel ( Fig. 4 View Fig in Nelson and Kondratieff 1988) and exhibits some dorsoventral flattening in the anterior third. Its median dorsal groove extends to one-half the epiproct length and a dorsal row of 4-6 anteriorly directed stiff setae or spines occur on each side of the median groove in the anterior third. A median knob is present on tergum 7, but the pair of knobs is absent from tergum 9.

Sierracapnia   demonstrates similarities with the three species of the Capnia mariposa   species group sensu Nelson and Baumann (1989), especially with C. giulianii Nelson and Baumann 1987   and C. mariposa Nelson and Baumann 1987   . In these two species, the epiproct exhibits varying degrees of lateral compression, a keeled ventral surface, dorsolateral horns, a large exposed dorsal membrane, and an eversible crest, plus tergum 9 has a pair of median knobs. Additionally, the C. mariposa   species group is restricted to the Sierra Nevada. The Capnia mariposa   group was excluded from Sierracapnia   because all three species lack a knob on tergum 7 and the dorsolateral horns are small and restricted to the tip of the epiproct.

The identification key for Capnia   males in Nelson and Baumann (1989) separates Sierracapnia   (then defined as the C. barberi   species group) from nine other Capnia species   groups and several unplaced species found in North America, but does not separate Capnia species   groups found in the Palaearctic. With the exceptions noted above for three Arsapnia species   , Sierracapnia   differs from Arsapnia   and all other Capnia species   groups of North America by having distinct median knobs on terga 7 and 9, and lacking knobs on tergum 8. Further, except for two species of the Capnia mariposa   group, Sierracapnia   is unique among all other Capnia species   groups of North America by having a laterally compressed epiproct.

Distribution. The greatest diversity of Sierracapnia species   is found in the Sierra Nevada; this includes S. barberi   , S. mono   , S. shepardi   , and S. yosemite   ( Figs. 39 View Fig , 40 View Fig ). Closely adjacent to the eastern Sierra Nevada, two species, S. hornigi   and S. washoe   , occur in the White Mountains and northwestern Nevada, respectively. The distribution of S. barberi   extends northward into the southern Cascade Range. Sierracapnia palomar   , which occurs on several mountains of southern California, lies outside the rather compact distribution of the other six species of the genus. In addition to the distributional separation of S. palomar   , the shallow ventral curve and general linear proportions of its epiproct are obvious differences from the typical form of Sierracapnia   . Nevertheless, this species was included in Sierracapnia   because it bears knobs on terga 7 and 9 and its glabrous narrow epiproct has a ventral curved surface, dorsolateral horns, long membrane groove, and an apical eversible crest.

The distributions of Capnia   s. s. and Sierracapnia   do not overlap in western North America: Capnia   s. s. occurs in the far north; Sierracapnia   is found much further south in California and Nevada. In contrast, overlap exists in the distributions of some Sierracapnia   and Arsapnia   since the latter has a wide range in western North America, occurring from the central and southern Rocky Mountains to the Coast Range. Members of several other Capnia   s. l. species groups overlap broadly in their ranges with Sierracapnia   , Arsapnia   , and Capnia   s. s. in western North America. Sierracapnia species   inhabit midelevation, perennial, streams and creeks.

Etymology. The name Sierracapnia   reflects the primary Sierra Nevada distribution of the genus.

Table 1. Characters of Sierracapnia adult males. Ab7=abdominal segment 7, EP=epiproct, and EP neck (see Fig. 22).

Sierracapnia   n Ab7 knob Ab7 knob EP apex EP width/ EP depth/ EP Horn Horn EP
      width/ shape EP length EP length Membrane length/EP tip/EP Neck
      Ab7 width   (%) (%) color length length  
      (%)         (%) (%)  
barberi   5 thin, 9-13 thin, sharp 15-21 30-35 light 22-25 70-78 narrow
hornigi   5 thin, 11-16 rounded 17-24 19-24 light 15-18 76-85 narrow
    small notch                
mono   5 wide, 30-40 thin, sharp 16-23 32-35 light 16-20 67-75 thick
    deep notch                
palomar   5 thin, 13-17 wedged 13-15 12-14 light 15-17 92-95 narrow
    small notch                
shepardi   5 wide, 29-32 rounded 17-25 18-20 dark 14-18 80-86 narrow
    deep notch                
washoe   5 wide, 30-36 rounded 22-26 22-26 dark 24-29 83-88 narrow
    deep notch                
yosemite   5 thin, 14-15 rounded 18-24 25-30 light 18-21 85-88 narrow
    notched tip