Caucasusacalles circularis Stüben, 2025

Stüben, Peter E., 2025, New species and an image key to the wingless Cryptorhynchinae of the Caucasus (Coleoptera: Curculionidae: Tylodina) - a hypothesis on the spread of forest and open land species in the Western Palaearctic, Zootaxa 5647 (3), pp. 235-259 : 240-242

Caucasusacalles circularis Stüben sp. nov.

urn:lsid:zoobank.org:act:E2F97031-00B7-4CD8-B25B-FB2852505807

( Fig. 4 )

Type material

Holotype: 1♂, ‘ Armenia: around Arakelots Monastery ruins, W Kirants, Tavush, 21.5.2022, leaf litter sifting and Winkler extractor, 41,032000 45,066000, deciduous forest, leg. Astrin’, coll. ZFMK, ZFMK-TIS-8010636 , mtCO1 sequence see Appendix 2; for photo documentation see Fig. 4 // Paratypes: 1♂, ‘ Georgia: 9 km E of Tianeti, on Aniskhevi River banks, forest next to river and affluent creek, Mzkheta-Mtianeti , 42,08619 45,04298, 1051 m, leg. Astrin’, coll. Stüben, mtCO1 sequence see Appendix 2 / 1♂, ‘ Georgia: E of Saparlo , Kvemo Kartli, 41,3021 44,3178, Quercus , 16.11.2023, leg. Astrin’, coll. ZFMK, ZFMK-TIS-8028288 , mtCO1 sequence see Appendix 2 / 1♂, 3♀, ‘ Georgia, Kharagauli, Merelisi env., 482 m, 41°56'26"N 43°17'01"E, 29.8.2019, sifting in mixed forest, lgt. Baňař, Hlaváč, Barjadze & Maghradze’, coll Krátký / 1♂, ‘ Georgia: „Kaukasus, Suram-Pass”, „ Acalles lederi Meyer <handwriting>, Penecke det.’, coll. Senckenberg Naturhistorische Sammlungen Dresden / Georgia: 1♂, ’Suram-Pass, 2010, Kulzer”, “ Acalles choudoiri, Zumpt det.’, coll. Naturhistorisches Museum in Wien .

Description & differential diagnosis

Length. 2.1–2.5 mm (without rostrum)

The new species C. circularis from Armenia (type locality) as well as from central and southern Georgia hardly differs externally from the previously described species C. subglobosus . The few short, erect bristles on the very broad elytral intervals are also conspicuous in this species. Likewise, the adjacent scales on both the pronotum and the elytra are predominantly circular, characteristics that make these two species easily distinguishable from all other Cryptorhynchinae of the Caucasus .

While the elytra of C. circularis are somewhat more broadly rounded towards the apex (not slightly obovate as in C. subglobosus ) and the rostrum is somewhat more robust, deeper and longitudinally punctate towards the edges ( Fig. 4 ), the only reliable and constant distinguishing feature is the sclerite complex in the endophallus. In C. circularis this consists of widely spaced, parallel, narrow bars connected in the upper part by a pointed, but not so strongly sclerotised bridge as in C. circularis , whereas in C. subglobosus the sclerite consists of closely spaced bars, each with an inwardly inclined long, spine-like tip (compare Fig. 2 vs. Fig. 4 ).

In this character, C. circularis actually resembles C. lederi , the type species of the genus Caucasusacalles (type locality: Georgia, Svaneti Region). However, in C. lederi , the sclerite of the endophallus consists only of two simple, subparallel bars and does not show, as in C. circularis , further sclerotised, angularly separated, characteristic protuberances in the basal area as well as strongly curved ends (compare Fig. 3 vs. Fig. 4 ). In addition, the median lobe of the aedeagus is considerably shorter in this new species. The elytra of the new species are shorter and more broadly rounded towards the apex, whereas the elytra in most of the C. lederi specimens I have seen appear more elongate and are much more ovally rounded towards the apex. In any case, males of the three very similar Caucasusacalles species mentioned here can be easily distinguished by their differently shaped internal structures of the endophallus and specimens can be easily assigned to a species.

Molecularly, however, the females of C. subglobosus and C. circularis can be assigned to one of the species, because they are separated by 11% in the mitochondrial CO1 subgene (658pb, Follmer region). This is a very high value (compared to other western Palaearctic species of the Cryptorhynchinae , which differ more clearly in morphological terms) and undoubtedly distinguishes these as different species (for details see Schütte et al. 2023).

Distribution. This species is so far known only from specimens from Armenia and central and southern Georgia.

Derivatio nominis. The species epithet ‘ circularis ’ (Latin) refers to the almost circular elytra.

Figures

FIGURE 2. Habitus and aedeagus of the holotype of Caucasusacalles subglobosus sp. nov.

FIGURE 3. Habitus and aedeagus of Caucasusacalles lederi (Meyer, 1896) with the aedeagus and endophallus of the holotype (bottom right).

FIGURE 4. Habitus and aedeagus of the holotype of Caucasusacalles circularis sp. nov.