New and little-known bees of the genus Hylaeus Fabricius, 1793 (Hymenoptera, Colletidae) from the Caucasus region

New records on 32 species of the genus Hylaeus Fabricius, 1793 (Hymenoptera: Colletidae) from the Caucasus region are presented. Hylaeus alievi Dathe & Proshchalykin, sp. nov. is described from Azerbaijan. Eight species are newly recorded from the Caucasus: Hylaeus araxanus (Warncke, 1981), H. excelsus (Alfken, 1936), H. intermedius Förster, 1871, H. iranicus Dathe, 1980, H. kotschisus (Warncke, 1981), H. oblitus (Warncke, 1972), H. soror (Pérez, 1903), and H. trifidus (Alfken, 1936). In addition, ten species are newly recorded for Armenia, nine for Azerbaijan, four for Russia, and one for Georgia. An updated checklist of the 54 species of Hylaeus so far known from the Caucasus region is provided.


Introduction
The present study is the preliminarily last part of a series of papers dealing with the bees of the genus Hylaeus Fabricius, 1793 from the territory of the former Soviet Union (Proshchalykin and Dathe 2012Dathe , 2016aDathe , 2016b The records are first sorted alphabetically according to the countries, and then chronologically according to the locality.
For the species distribution, we use the following terms from a European perspective: Asia minor Turkey (Asian part); Near East Arab states (especially Syria, Lebanon, Jordan, Iraq and Iran), Israel; Middle East Afghanistan, Pakistan; Central Asia Kazakhstan, Uzbekistan, Turkmenistan, Kyrgyzstan, Tajikistan;

Far East
Russian Far East; Mongolia, China and Japan are mentioned separately.
The specimens were studied with a stereomicroscope Olympus SZX12, the photos taken with a Leica Application Suite vs. 4.12. The stacks of digital images were processed using Helicon Focus 7.6.4.

Hylaeus (Abrupta) cornutus Curtis, 1831
Material examined. AzerbAijAn: Nakhichevan AR, Shakhbuz, Shakhbuzkend, 22.VII.2018, (1 ♀) Distribution. Mediterranean to Central Asia. Diagnosis. This is a small species of the brevicornis group with a short head. In the species of this group (Dathe 1980b: 232;Michener 2007: 204) the metasomal terga are distinctly shagreen and densely punctate; particularly characteristic is the genital capsule of males with curved penis valves with basal tooth in dorsal view (Fig. 8). This male is hardly separable using conventional characters from similar species with a strongly thickened scape and blunt bicuspid transverse callus on S3. However, the peculiar shape of apical lobes of S7, with long bristles, is unique in the group. The female is unknown.
Female. Unknown. Etymology. We dedicate the new species to our friend and colleague Dr. Khalid Ali Aliyev  in his honorable memory. He added significantly to the knowledge of the bee fauna of Transcaucasia and was actively involved in the expeditions which yielded the material assessed here.

Conclusion
In total, 54 species of Hylaeus are recorded from the Caucasus (Table 1). This is a comparable number to the Iranian fauna -52 species (Ascher and Pickering 2021), but distinctly less in comparison with the adjacent fauna of Turkey -86 species (Özbek and Dathe 2020), and Central Asia -70 species (Dathe and Proshchalykin 2018). The real number of species of Hylaeus in the Caucasus may be at least one third more. Further studies will certainly reveal many species new not only to Caucasian fauna but also to science. It would be worthwhile to examine the Caucasus more closely also with regard to its zoogeographic features. From the genus Hylaeus, various elements of the Western Palaearctic, Near East and Central Asian faunas come together here. Genetic evidence from various animal groups had shown that glacial refugia existed in the Caucasus, from which parts of the Western Palaearctic were colonised postglacially, similarly to colonisation of large areas of Eastern Europe from the Ciscaucasus (Schmitt 2020).
We provide new information in support of this view ( between several zoogeographical regions. However, a detailed faunistic analysis of the genus Hylaeus in the Caucasus is not yet possible, since a considerable number of its members apparently remains unrecorded for this area. This is also shown by the relatively numerous new records, eight for the Caucasus alone -H. araxanus (Warncke, 1981), H. excelsus (Alfken, 1936), H. intermedius Förster, 1871, H. iranicus Dathe, 1980, H. kotschisus (Warncke, 1981, H. oblitus (Warncke, 1972), H. soror (Pérez, 1903, and H. trifidus (Alfken, 1936) -as well as for individual countries, with ten species new for Armenia, nine for Azerbaijan, four for Russia, and one for Georgia.