Capnia Pictet 1841, sensu lato

Capnia Pictet, 1841 sensu lato

(Figs. 11–16, 26–28, 36–38)

Capnia Pictet, 1841 — Nelson & Baumann 1989: 291. (revision of the Nearctic species, partly refers to Arsapnia Banks, 1897 and Capnia Pictet, 1841 sensu stricto); Zhiltzova 2003: 318. (revision of the Palaearctic species (excluded Japan and the Himalayan ranges), partly refers to Capnia Pictet, 1841 sensu stricto and Zwicknia Murányi, gen. n.).

Species included. In addition to the species treated as Capnia s.s. above, 1 valid species from the West Palaearctic, 49 from the East Palaearctic, 46 from the West Nearctic and 1 is Transnearctic (DeWalt et al. 2014, Nelson & Baumann 1989); 47 examined (see Appendix 1).

Remarks. An adequate diagnosis cannot be given for this artificial assemblage of taxa, and the species excluded from the sensu stricto diagnosis will need to be placed in existing or newly erected genera. A revision of these species is out of the scope of the present work, and most of the East Palaearctic species were not studied; some remarks on certain groups can be made on the basis of species examined:

Capnia s.l. cordata species group sensu Zhiltzova 2001

This group is restricted to the high mountains of Asia with nine known species (Li & Yang 2009, Li et al. 2011, Zhiltzova 2003); three further species, known from only females, are attributed to this group on the basis of the female genitalia (Zhiltzova 2003). Morphologically they form a rather uniform lineage that is closer to Zwicknia, but distinctly differs in the males with entire Ep-scl and the lack of Ec (studied in C. s.l. prolongata Zhiltzova, 1969: Figs. 11–12), and females have a narrow, dark Sg.

Capnia s.l. excavata and C. s.l. nana groups sensu Nelson & Baumann 1989

As mentioned above, these West Nearctic groups of three and six species (Nelson & Baumann 1989) may belong to the genus Arsapnia. The morphology of their epiproct is similar, however, distinctly differ in shape.

Capnia s.l. fialai Nelson & Baumann, 1990

In its original description, this Californian, U.S.A. species was noted for its resemblance to Paracapnia Hanson, 1946 in many features. Recently, it was suggested by Kondratieff & Lee (2010) that C. fialai could be placed in Paracapnia. Despite obvious similarities, we propose to retain it in Capnia s.l. pending further comparative studies, because of the presence of caudal setae on the epiproctal sclerite and tergal processes on Tg 5–7. These features are lacking on other species currently placed in Paracapnia. Their inclusion in the generic diagnosis should further restrict the already few diagnostic features of that genus.

Capnia s.l. gracilaria and C. s.l. vernalis groups sensu Nelson & Baumann 1989

With respect to the structure of their terminalia, these Nearctic groups of four and three species (Nelson & Baumann 1989) probably belong to the genus Mesocapnia Raušer, 1968, with the exception of C. lacustra Jewett, 1965 (see below). The distinctive apical spine of the epiproct of Mesocapnia was thought to be a compact structure (Baumann et al. 1977, Raušer 1968, Nelson & Baumann 1989). However, SEM studies showed that it is a dorsally open structure like the epiproct apex of any other Capniidae (Lee & Baumann 2011). Capnia s.l. zukeli Hanson, 1943, a species from Idaho that was not classified in these species groups by Nelson & Baumann (1989), probably also belongs to Mesocapnia.

Capnia s.l. lacustra Jewett, 1965

This odd species, restricted to Lake Tahoe, Nevada, U.S.A. is aquatic in both the larval and adult stages, differing from all other Capniidae by having Tg 10 entire, and exceptionally reduced ventral thoracic sclerites. The male terminalia is closer to Mesocapnia but differ in lacking caudal setae on the epiproct. However, its designation as a separate genus would need further specimens for study. The few available specimens are nearly transparent and morphological details were difficult to ascertain using stereomicroscopes. Specimens were not examined by SEM to avoid damaging these specimens. It is worthy to note that one of the females examined, the entire abdomen and thorax to the cervical region was filled with eggs, a further uniqueness that may be related to the exceptional underwater life of this species.

Capnia s.l. nelsoni Kondratieff & Baumann, 2002

The species was related to the C. s.l. decepta group in its original description, but the authors reluctantly placed it in the above group because of notable morphological differences (Kondratieff & Baumann 2002, Heinold et al. 2013). Indeed, its genital characters differ greatly from the diagnosis of Arsapnia (C. s.l. nelsoni has large B-scl, Lb-scl divided from Ep-scl and Ep-scl is longitudinally divided), but also cannot placed in any existing groups.

Capnia s.l. pedestris species group sensu Zwick & Sivec 1980

This group was erected for nine, mainly Central Asian species and two additional species known only from females (Alouf 1992, Zhiltzova 2003, Zwick & Sivec 1980). The main distinguishing character in males is a highly developed, bicuspidate Tg 9. In addition, these taxa are characterized by laterally and dorsally reduced Ep-scl and a large B-scl (Figs. 13–16). However, the studied C. s.l. pedestris Kimmins, 1946 and C. s.l. arensi Zhiltzova, 1964 differ in many features of the terminalia (Figs 13–16, 27–28, 36, 38), and at least the latter Caucasian-Anatolian species is not monophyletic with the rest of the group.

Capnia s.l. spinulosa Claassen, 1937

This species from California, U.S.A. has both laterally and ventrally highly divided Ep-scl. The large, complex membranous parts of the epiproct lack I-scl but possess an Ec, and the Fp is fused with Rp. The combination of these genital features does not occur in any of the other species studied during this study, but this taxon may belong to the East Palaearctic genera Takagripopteryx or Capniella.

Capnia s.l. valhalla Nelson & Baumann, 1987

Despite superficial resemblance to Capnia sensu stricto, the epiproctal structure of another California, U.S.A. restricted species, is similar to Allocapnia. However, it differs from Allocapnia by having a long and narrow Fp, and Sg fused with St 9 but not with Tg 9; the latter feature occur only in Capnura Banks, 1900 among the studied taxa (see Fig. 43). Most probably, this species should be placed into a separate genus, but comparative studies with the East Palaearctic genera will be needed.

Capnia s.l. vidua Klapálek, 1904

It shares all the characters enumerated in the diagnosis of Allocapnia, regarding also to the rather special structure of the epiproct (Figs. 5–6, Tables 1–5); similarities were already mentioned by Zwick (1973). Its classification in the previously strictly East Nearctic genus would explain its peculiar distribution, as the only stonefly found in Iceland. This species additionally has a patchy distribution in southeastern Europe through the N British Isles and NW Scandinavia, with five named subspecies (Fochetti 2004, Hynes 1955b, Lillehammer 1972, Lillehammer et al. 1986, Vinçon & Sivec 2011). However, molecular studies do not readily confirm the morphological characteristics, and further studies are needed to clarify the generic placement.