Isocapnia Banks, 1938

(Figs. 19–20, 30, 35)

Isocapnia Banks, 1938 — Banks 1938: 73. (original description, type species Arsapnia grandis Banks, 1907); Zhiltzova 2003: 398. (revision of the Palaearctic species); Zenger & Baumann 2004: 66. (revision of the Nearctic species).

Diagnosis. Male epiproct: B-scl large, divided from Ep-scl; Lb-scl small, divided from Ep-scl; Ep-scl entire both ventrally and laterally, caudal setae absent; I-scl and Ec absent. Male Pp: apical part long and wide; Fp long and very narrow, divided from Rp. Male Sg: divided from St 9 and Tg 9, vesicle present. Female Sg: rectangular, entire or weak centrally; inner and lateral sclerites absent. Male tergites: process lacking or Tg 9 with process. Ventral thoracic sclerites: MPrs elliptical or triangular, MeFs transverse, MeFsp fused with MePfs; Prs/Bs, Mfs/St 1 and PPo/PFs fused with or separated from. Macropterous wings: forewing A1 beyond a and R1 before r straight; crossveins between C and Sc one to eight, R veins three to five.

Species included. 12 valid species from the West Nearctic and 7 from the East Palaearctic (DeWalt et al. 2014); 15 of these examined (see Appendix 1).

Remarks. Some of the diagnostic characters widely used since Hanson (1946) are variable within the species included (Tables 1–2). Nevertheless, the structure of the male terminalia is similar in the species having differently shaped epiprocts ( I. vedderensis (Ricker, 1943), I. spenceri Ricker, 1943). Reduction of the number of forewing C-Sc crossveins occurs in the small-sized species. Veins not counted in the case of the species having odd, reticulated wing venation ( I. palousa Zenger & Baumann, 2004, I. mogila Ricker, 1959 – see Zenger & Baumann 2004: Fig. 26).