Cryptotendipes darbyi (Sublette)

(Figure 1)

Tendipes darbyi Sublette, 1960: 221.

Tendipes ariel Sublette, 1960: 222.

Cryptotendipes darbyi: Saether 1977: 97, 2010: 12; Hayford 2005: 197.

Mongolchironomus mongoljekeus Sasa & Suzuki, 1997: 159, syn. nov.

Material examined. Holotype of Mongolchironomus mongoljekeus, M (NSMT-I-Dip 5053), labelled “No. 308:84”. MONGOLIA: Bogd #9, 44°40'N, 102°11'E, alt. 1500 m, 13.viii.1996, leg. H. Suzuki; 1 M, MONGOLIA: Hyargas Nuur, 20.viii.2019, leg. Q. Han; 4 M, CHINA: Qinghai Province, Lake Qinghai, Daotang stream, 36°34'N, 100°44'E, alt. 3200 m, 12.vii.2023, leg. S. Wang; 1 Pe, 3 L, Qinghai Province, Lake Qinghai catchment, a freshwater bog near Gahai, 37°1'N, 100°32'E, alt., 3210 m, 27.vi.2016, leg. J. Liu; 1M (ZSM), RUSSIA: Zabaykalsky Krai, Tshita, Barun-Torei Lake, Cape Myrgen, 20.vi.1994, leg. V. G. Shilenkov.

Remarks. The examined holotype (Fig. 1B) has a relatively slender, spatulate anal point, contrary to the portrayed stout, parallel-sided anal point in the original illustrations (Sasa & Suzuki 1997: 160, figs 11j, 11k). The dorsal surface of superior volsella is nearly entirely microtrichiose, and bare on the ventral surface. The ventral tubercles (Fig. 1C) under T IX are rolled upward. The fused anal tergite band is not well illustrated. A new hypopygium illustration (Fig. 1C) based on the holotype is shown here, with those of the superior volsella and anal tergite band (Figs 1F, I) varying in the perceived shape depending on the mounting orientation on the glass slide and pressure from the cover glass.

The morphological features of the specimens collected from China, Mongolia and Russia are consist with those of the holotype of Mongolchironomus mongoljekeus Sasa & Suzuki. These specimens undoubtedly belong to the same species. The species is characterised by the color pattern of legs (foreleg entirely dark-brown and mid and hind legs dark-brown only on the tarsi), the scutum with 3–4 pairs of acrostichal setae on the middle, the male with the pad-like, microtrichiose superior volsella with a row of several anterior setae. Further, the males of Asian populations examined here have following features: head with weak or no frontal tubercle, total length 3.1–4.7 mm, wing length 1.5–2.2 mm, AR 2.23–2.68, and LR 1 1.35–1.48. These fall into the range of variation described by Sublette (1960) and Saether (2010) for Nearctic specimens. The specimen collected from Russia by V. G. Shilenkov, now deposited in Zoologische Staatssammlung, München, Germany (ZSM) satisfies these features (M. Spies, ZSM, Germany, pers. comm.).

The BLAST analysis showed that our barcode sequences (DBCCT012-24, DBCCT013-24, DBCCT014-24) have a high similarity (> 98.5%) with that in the Canadian material identified as Cryptotendipes darbyi (accession numbers KR633331, KR618562, KR642352, KX281738), of which morphological features are consistent with those of our material, too.

Distribution. The species has a Holarctic distribution, from North America (USA and Canada) to Europe (Central Finland), and further to the Mongolian Plateau and the Tibetan Plateau in Asia. The distribution is shown in Fig. 3.