Plateumaris caucasica Zaitzev, 1930

Geiser, Elisabeth, 2023, Revision of the Palaearctic species of the genus Plateumaris C. G. Thomson, 1859 (Coleoptera, Chrysomelidae, Donaciinae), ZooKeys 1177, pp. 167-233 : 167

Plateumaris caucasica Zaitzev, 1930 syn. nov.

Type locality.

Russia: Stavropol and Dagestan.

Type material.

Type series: Russia • 4 ex; Ciscaucasia, Stavropol; Apr 1905; DM Maljuzhenko leg.; Russia • 5 ex; Daghestan, Chasav-jurt; E. Koenig leg.

Remarks.

According to Zaitzev (1930) these specimens were stored in the "Collection of the Georgian Museum". The currently depository is unknown.

Geiser (in press) and Geiser and Bezděk (in press) treated P. caucasica as a synonym of P. sericea "based on study of comparative material, descriptions, and of biogeographical research". Zaitzev (1930) described a new species Plateumaris caucasica (see Geiser and Geiser 2023) based on reddish parts of the antennomeres and legs. Additionally, he stated as different characters: "a more rugose pronotum (almost like P. discolor )" and "compared with P. discolor more slender antennae, the fourth antennomere which is twice as large as the second". Also, he stated, it is a "intermediate species between Plateumaris sericea L. and Plateumaris discolor Panz."

As I explained in "General remarks on synonyms of Plateumaris sericea " above, this is a typical example of establishing a new “species” on colour characters. The other mentioned “different” characters are completely within the variation range of P. sericea or characteristic of this species. The morphology of the aedeagus is also completely within the variation range of P. sericea . In the same area also typical P. sericea (that is: with completely metallic antennae and legs) could be found, the colour variation form " P. sericea caucasica " could not even be a subspecies.

Zaitzev assumed that Plateumaris caucasica is also "very close" to P. annularis , because both have a red base at their antennomeres and legs which are partly reddish brown. To the credit of Zaitzev it is necessary to mention that he had doubts if P. caucasica is really a new species or a synonym to P. annularis . He suggested to treat it as a new species until further knowledge is available about the East Siberian Plateumaris species.

Plateumaris annularis was synonymised by Kolossow (1930) with P. roscida (see there for details). Askevold (1991) suggested that " Donacia caucasica ( Zaitzev) (1930: 11)" [sic! it was described it as Plateumaris and not as Donacia ] is a "possible new synonym" to P. roscida . He argued that both have the red base of the antennomeres and the description of Zaitzev agrees well with specimens of P. roscida , but he had doubts because P. roscida is known only from Asia east of lake Baikal whereas P. caucasica only occurs in the Caucasus region.

First, it is actually biogeographically implausible that these two species should be synonyms. Second, the pygidium is emarginate in P. roscida and not emarginate in P. caucasica in both sexes. Third, the aedeagi of P. roscida and P. caucasica are strikingly different. For the median lobe of P. roscida see Fig. 9 . The median lobe of P. caucasica fits well into the variation range of P. sericea (Fig. 11D, E ). Therefore P. caucasica is a synonym of P. sericea .

Bieńkowski (2014) stated in his identification key at P. sericea : The taxonomic status of the subspecies Plateumaris sericea caucasica and Plateumaris sericea sibirica needs further studies. This has been done here for Plateumaris sericea caucasica and Plateumaris sericea sibirica (see below).

Material examined.

More than 30 specimens from the Caucasus region (north and south) labelled as " P. caucasica ", " P. sericea caucasica " or " P. roscida " which were all clearly P. sericea .

Figures

Figure 9. Plateumaris roscida aedeagus, photographed from different angles and drawings in frontal view A, B specimen from Primorsky Krai (ZMS) C specimen from Amur Oblast (NHMB) D median lobe E cap of tegmen (A-C photographs by E. Geiser, D, E drawings by G. Geiser). Scale bars: 1 mm.

Figure 11. Plateumaris sericea A-C habitus illustrating variability in colours, but there are more D, E aedeagus: two examples of the variability of the shape of the median lobe (photographs by K. Matsumoto). Scale bars: one unit - 1 mm.