2Tuvinian Institute of Complex Exploitation of Natural Resources, Kyzyl, Tyva Republic, Russia.

The Tyva Republic (or Tuva) embraces the sources of the great Siberian River Enisei. It is mostly surrounded with rather high (up to 3970 m) mountains of Altai, West and East Sayans, Hangai, and embraces a number of its own mountain systems, which subdivide it into several huge intermontane hollows. At its capitol Kyzyl the geographical centre of Asia is situated. Generally Tuva has a sharply continental climate characteized by a low average year tempeature (-4oC) with extreme circannual amplitudes (-54 - +40oC) and mostly low annual precipitation (to 200-220 mm). The huge Todzha Intermontane Hollow, situated in the NE of Tuva and being the catchment of the Bii-Khem (Great Enisei) River is, on the contrary, rather humid and woody. The Tuva represents an exciting amalgamation of Mongolian semideserts and dry steppes and Siberian larch taiga and highland tundras. This vaste and natural territory was hitherto unexplored in an odonatological respect.

Regular collection of odonates has been started in Tyva in 1988 by one of us (V. Z.), in 2000 the other author (O. K.) undertook a special expedition, partly supported by IDF, which was devoted to the dragonfly fauna. Presently the species composition of theTuvinian fauna is known rather well, but details of its distribution is a subject for further studies. The Turan Hollow and the Kaa-Khem River basin remained completely unexplored.

The up to date list of the Tuvinian odonatofauna includes 41 species, up to 12 more species could be expected. Most interesting appeared to be a comparison of the fauna of the Todzha Hollow with that of the rest of Tuva. The most interesting findings are as follows. Calopteryx splendens (Harris, 1782) was found in Todzha only, where it seems to be represented by rather typical population on the Dus-Khem River but by a population with extremely enlarged coloured areas on the wing and androchromic females on the Toora-Khem River. The main arid territory of Tuva is inhabited by Enallagma cyathigerum risi Schmidt, 1961 but in the Todzha Hollow Enallagma cyathigerum cyathigerum Charpentier, 1840 ab. continentale Belyshev, 1956 was found out. That is, these well differing subspecies, usually regarded as species, are separated only by the Academician Obruchev Mts. Moreover, the nominotypical subspecie is represented by aberration with black stripes on the abdomen sides, characteristic to the extreme NE Asia. Analogously, Todzha is inhabited by Coenagrion hastulatum (Charpentier, 1825) while the rest of Tuva - by a very close species C. lanceolatum (Selys, 1872). In Tuva there were found two species of Ophiogomphus: O. obscurus Bartenev, 1930, connected with the taiga regions, in the Todzha Hollow and the Mongolian-Chinese species O. spinicornis Selys, 1878 in the Ubsu-Nur and Khemchik Hollows (no species was recorded for the Central Tuvinian Hollow). In Todzha Hollow, on the Toora-Khem River, we have found sympatricity, without intergradation, of Somatochlora metallica abocanica Belyshev, 1955 and S. exuberata Bartenev, 1910, that corroborates species independence of the latter. Finding of Aeshna affinis Van der Linden, 1825 in the Ubsu-Nur Hollow protruded its known range in Siberia to the east. The following interesting species were recorded as rare: Lestes macrostigma Eversmann, 1836, Ischnura elegans (Van der Linden, 1820), Sympetrum tibiale Ris, 1897.