Revision of the Palaearctic species of the genus Plateumaris C. G. Thomson, 1859 (Coleoptera, Chrysomelidae, Donaciinae)

Abstract Ten of the 27 species of Plateumaris Thomson (Chrysomelidae: Donaciinae) occur in the Palaearctic. Due to the intraspecific variation and the large distributions of some species, descriptions exist for at least 80 taxa plus five nomina nuda. The status of each valid species is clarified and the remaining 70 names are allocated as synonyms. New synonymies are P.tenuicornis Balthasar, considered a synonym of P.consimilis (Schrank), P.sulcifrons Weise as a synonym of P.rustica (Kunze), and P.caucasica Zaitzev as a synonym of P.sericea (Linnaeus). Two controversial synonyms are confirmed: P.discolor (Panzer) and P.sericeasibirica (Solsky) are both synonyms of P.sericea. Finally, P.obsoleta Jacobson is a synonym but at present it is not possible to decide whether it belongs to P.shirahatai Kimoto or to P.sericea. Forty-one new country records are added, compared with the Catalogue of Palaearctic Coleoptera published in 2010; 28 records are based on recently published records and 13 are first records for a specific country.


Introduction
The genus Plateumaris Thomson, 1859 belongs to the subfamily Donaciinae (reed beetles) which is part of the beetle family Chrysomelidae (leaf beetles). This family includes more than 37,000 (probably at least 50,000) species in more than 2,500 genera, making up one of the largest beetle families (Jolivet et al. 1988). The Donaciinae comprise approximately 180 species belonging to six genera (Geiser 2015). Seventeen species of Plateumaris occur in the Nearctic region (Askevold 1991) and ten species in the Palaearctic region. Their distribution area extends from 30° north latitude to the Arctic Circle (pers. obs.).
Most life stages in Chrysomelidae (larvae and imagines) are terrestrial; however, the larvae of the Donaciinae develop submerged on roots of aquatic plants. These larvae breathe by tapping the aerenchyma of the plant with two hollow abdominal hooks which are connected to their tracheal system. Therefore, they can stay permanently under water. Monophyly of Donaciinae is supported by these special morphological and physiological adaptions as well as by molecular data (Kölsch and Pedersen 2008;Sota et al. 2008). These molecular analyses also revealed that the genus Plateumaris is a monophylum within the Donaciinae.
This number of ten species in the Palaearctic is not without controversy; in fact, different authors recognise nine to 19 species in the region (Table 1). This problem became virulent when I was editing the Donaciinae for the update of the catalogue of Palaearctic Chrysomelidae (Löbl and Smetana 2010;Silfverberg 2010), where the Plateumaris species are listed. To decide how many species occur in the Palaearctic region and what are their valid names, it became clear that a major revision was necessary. Simultaneously, several comprehensive works were published on Palaearctic Donaciinae, e.g., the 'Identification Key on Palaearctic Chrysomelidae' by Warchałowski (2010) and the book by Bieńkowski (2014) on the Russian Donaciinae, where almost all the Palaearctic Plateumaris species were treated. Hayashi (2020) dealt only with the Japanese Donaciinae that include half the Palaearctic Plateumaris species; his text complements Bieńkowski's book. Finally, the molecular analyses of Hayashi and Sota (2014) are an invaluable help with systematic revisions.
A revision of the Palaearctic species of Plateumaris was needed, not only for the Palaearctic catalogue (Bezděk and Sekerka in press; Geiser in press). Colleagues working in physiology or ecology, especially in applied limnology, or those who are trying to reconstruct the dynamics of postglacial resettlement and similar topics which are important to understand climate changes and threat to biodiversity, all rely on solid species delimitations.
Knowledge of species distributions is necessary for systematic revisions. Therefore, I evaluated records from museum specimens and the literature. For the catalogue (Geiser in press) I provided this information only in a very concise manner. A revision is a good place to publish the detailed data and also provides an opportunity to explain the significance of a new record. For systematic revisions it is mandatory to study the first description of the taxa concerned. Many of these descriptions are in Latin or at least begin with Latin text. To make my arguments more understandable a companion article in this issue (Geiser and Geiser 2023) is published, where translations are provided of many original descriptions into English.
collection: the location where the specimen is stored. det.
determinavit: name of the person who identified this specimen. ex.
previous collection where the specimen was stored. f. forma.

ICZN
International Code of Zoological Nomenclature. leg.
legit: name of the person who collected this specimen. T1, T2, … number of a tarsomere. var.
vidit: name of the person who confirmed the identification.

[ ]
Text in square brackets [ ] are additions or comments by the author; in records data they do not form part of the label text tagged to the specimen.

[leg.]
name of the person who probably collected this specimen.

[det.]
name of the person who probably identified this specimen.

[new in PalCat]
This indicates that the country mentioned was not listed in Silfverberg (2010) but is now listed in the update of the Palaearctic Catalogue (Geiser in press). This refers to already published records, and the data source is listed below.

[first record]
If a country record was not published in detail until now, it is indicated as "first country record". The same applies for a part of a country if it is treated as separate unit within a country, according to Bezděk and Sekerka (in press). These records were published in Geiser (in press) but only with the country or province abbreviation in most cases so the record details are given here.

//
If original text is cited from different labels tagged to the pin of one specimen, the double slash indicates the text separation between these labels.

Museum specimens
Except for Plateumaris sericea, it is very difficult to deliberately catch Plateumaris specimens in their habitat. Many voucher specimens were gained as by-catch in field studies motivated by other goals. The study of the variation of characters from many different sites of the whole distribution area is important for systematic revisions. Therefore, museum collections that have existed for a long time and where specimens from many different locations are stored are essential for such studies, but even smaller collections could provide a pleasant surprise to find some voucher specimens of a rare species from an interesting site. The specimens in the museum collections were sorted in boxes with a species label. The compilation was usually done by non-specialists, who sorted the various collections donated to the museum into the overall collection, regardless of whether they were correctly identified or not. The vouchers of P. bracata, P. consimilis, P. rustica, and P. sericea were usually correctly identified. Specimens of other Plateumaris species are rare, and these were all examined in detail. Some of them already had identifier labels. If not, I tagged my label on the needle with the information "genus species Author det. E. Geiser Year". I also did that when a specimen was misidentified, leaving the original identifier label on the needle. When a species was difficult to identify I used a similar label, with "vid. E. Geiser Year" to state that I have confirmed the identification. Specimens of the four species mentioned above were also studied carefully for the purpose of this revision. Here I did not tag my label to all of them, but mainly on vouchers that showed some variation of the typical characters or were collected in an interesting location.
The importance of museum collections has increased in recent years. Some areas of the Palaearctic region are inaccessible today for political or security reasons like Xinjiang in western China, or Syria, or Afghanistan. Fortunately, some natural history field studies dating more than 100 years ago enabled vouchers to be deposited in European museums. These historic specimens are an invaluable source for further studies. Additionally, it is more difficult today to collect Donaciinae and therefore Plateumaris species because man-made changes of limnic and wetland environments are contributing to the decline of habitats and, therefore, of species. Many previous habitats no longer exist and the only chance to study specimens from these districts is to examine the museum vouchers.

Main literature sources
In addition to the museum specimens studied, the author relied on certain important publications for additional data, mainly Hayashi (2020), Askevold (1991), and Bieńkowski (2014). Hayashi (2020) is a comprehensive recent study on Japanese Donaciinae which comprises five of the ten Palaearctic Plateumaris species occurring. Two species (P. akiensis and P. constricticollis with its three subspecies) are endemic in Japan, P. shirahatai is restricted to the East Palaearctic, and P. sericea and P. weisei occur across the Palaearctic region. Some figures and texts parts from Hayashi (2020) are cited here. The extensive study of Askevold (1991) on the Nearctic Plateumaris species is also important because it contains significant information about the Palaearctic Plateumaris species, and much information about the taxonomic aberrations affecting the genus. The comprehensive book of Bieńkowski (2014) on the Donaciinae of Russia was also helpful because this country covers a large part of the Palaearctic region and most of the Palaearctic Plateumaris species occur here. It also contains information about biology, ecology, food plants, and larvae of Plateumaris.

Original descriptions and type specimens
The study of original taxonomic descriptions is essential for any systematic revision. Many of the species or subspecies were first described in Latin with very specific phrases used in scientific entomological scripts in the 18 th and 19 th centuries. Some original descriptions are in German, French, or Russian; some are multilingual, starting with Latin for the main characters of a presumed new species, and then more details were added in the native language of the author. Therefore, to overcome these challenges, Geiser and Geiser (2023) present the original descriptions and their translations of all Palaearctic Plateumaris species including many synonyms. That comprises seven species, because three were originally described in English, and 19 taxa are now synonyms.
The study of type specimens is also essential in revisions, and I was able to examine six type specimens. Many types from the 18 th and 19 th centuries could not be located or no longer exist. Another problem is that specimens in collections may be labelled as "type" or indicated as types by red or red-bordered labels but are not actually type specimens.

Synonyms
For each species, in "Taxonomic history and synonymies" most synonymies are explained, where changes were made (Geiser in press) compared to Silfverberg (2010). Also, I attempted to provide the reference for the synonymisation. Although the literature was studied thoroughly, I could not track down this information in most cases. Some publications that are repeatedly cited in the literature in fact did not contain this information at all. Some synonyms listed here are confirmations of synonyms elaborated by previous authors but not accepted by some authors. In most cases new arguments are presented to validate these synonymisations.

Distribution data
For each species, the countries, or the part of a country, with reliable records are listed. Detailed information on the data source is given for the countries or part of a country which are new in Geiser (in press) compared to Silfverberg (2010). The subdivisions of some large countries (e.g., Russia, China) are the same in this work as in Bezděk and Sekerka (in press).

Identification keys
Many previous researchers have published keys to the Palaearctic species of Plateumaris, but these keys often use characters that are difficult to see from the beginning. Although only ten species occur in the Palaearctic region, some specimens are not easy to identify even for experienced coleopterologists. The new key reduces the species designation available for a particular specimen. The detailed characters and the pictures provided in the species sections should allow definitive identification. Because only two species occur in the whole Palaearctic region, the separation of the West and East Palaearctic in different keys leads to more reliable identifications. If the information on the specimen location label is very imprecise (e.g., "Siberia" or "Russia") then both keys need to be applied. Antennae and legs entirely metallic, same colour as pronotum and elytra. Sometimes the antennomeres can be reddish near the joints. At the legs small reddish parts may be occur near the joints or, exceptionally, on the tibiae or tarsomeres. Pronotum and elytra in various metallic colours (Fig. 11 Metafemoral tooth present but blunt, pronotum neither distinctly cordate nor flattened, outline subquadrate, slightly longer than wide, basal part narrowed, slightly cone-shaped, anterior tubercles distinctly visible or almost entirely smooth, upper side cupreous or bronze, sometimes

Opinions on species delimitation in the literature
Although only a few Palaearctic Plateumaris species exist (compared with other beetle genera), there are many differing opinions between authors. Almost every comprehensive publication about Palaearctic Plateumaris shows a different number of species (Table 1). The highest number of species is recorded by Borowiec (1984): he regarded 17 species as valid. At that time P. akiensis was not described and P. amurensis was regarded as a synonym of P. weisei. Therefore, two more species can be added. Goecke (1960) mentioned 13 Plateumaris species for the Palaearctic region in his world checklist; three were not described then and he regarded P. amurensis as a synonym. Therefore, four more species must be added. In his major work about the Nearctic Plateumaris species, Askevold (1991) also treated the Palaearctic species. He established several synonyms, some of them as probable new synonyms. He regarded nine names as valid for Palaearctic Plateumaris species. I agree with his assessment except concerning P. amurensis, which he regarded to be synonymous with P. weisei.  showed that P. amurensis is a separate species, bringing the total to ten species.
Two major books were published in 2010: Warchalowski treated 12 species in his identification key and Silfverberg listed 16 species (and some more subspecies) in Löbl and Smetana (2010). Some large works which cover only a part of the Palaearctic region also contain invaluable information such as Bieńkowski (2014) on the Russian Donaciinae, which covers a large part of the Palaearctic region and almost all the Palaearctic Plateumaris species. The recent publication by Hayashi (2020) deals with the five Japanese Plateumaris species, which includes half of all the Palaearctic species; the paper contains the species that do not occur in Russia, so the Palaearctic region is completely covered with these two publications. Gressitt and Kimoto (1961) named four Plateumaris species in their comprehensive study on the Chrysomelidae of China and Korea; except for P. amurensis the other three names are synonyms.
1760: Linnaeus mentioned Leptura sericea in his 'Fauna Suecica' with the same diagnosis as in Linnaeus (1758) but with more details. Therefore, the species is sometimes cited as Leptura sericea Linnaeus, 1760(e.g., in Silfverberg 2010, but the first description date is clearly Linnaeus, 1758 (see Geiser and Geiser 2023 for original Latin text of Linnaeus and translation). 1762: Geoffroy erected the genus Prionus for the species Cerambyx coriarius Linnaeus, 1758. It now belongs to the Cerambycidae as does the genus Leptura.
1772: Scopoli described Prionus bracata. 1775: The genus name Donacia was erected by Fabricius. He described Donacia crassipes and Donacia simplex and assigned Leptura aquatica L., 1758 to the genus Donacia, but he did not change the genus name of Leptura sericea L., 1758. Other Plateumaris species were described as Leptura, e.g., Leptura consimilis Schrank, 1781. It is remarkable that these early entomologists had already assigned them to a genus other than Donacia.
1796: The category "familia" was established between order and genus for insects by Latreille. 1802: Latreille established the coleopteran family Chrysomelidae. 1837: Kirby established the subfamily Donaciinae. 1859: The genus name Plateumaris was erected by C. G. Thomson (translation in Geiser and Geiser 2023), but some authors, especially Americans, preferred Donacia as the genus name in their new descriptions. Even Marx (1957) regarded Plateumaris as a subgenus of Donacia. The Palaearctic Plateumaris weisei (Duvivier, 1885) and P. constricticollis (Jacoby, 1885) were also originally described as Donacia.
1920: Reitter split the Palaearctic Plateumaris into two subgenera: Plateumaris sensu stricto and Juliusina. He assigned P. sericea and P. discolor to Plateumaris s. str. and he described P. annularis in a footnote to P. sericea. In the same footnote he assigned P. obsoleta to P. annularis, but not as a synonym, and he placed P. amurensis near to P. discolor. The subgenus Juliusina contained P. bracata, P. consimilis, P. rustica, and P. affinis. To the latter species he assigned P. sulcifrons and P. mongolica. Moreover, Reitter made no designation of type specimens to either of the new subgenera.
Type species designations. Thomson (1859) stated "Typus P. nigra (FAB.) [= Fabricius]" in the original description of the genus Plateumaris, but most authors cited " Thomson, 1866" as the year of the original description. Thomson (1866) is an extensive book but contains no type designation because this had been done previously in 1859. Therefore, the prevailing opinion was that there existed no type designation for the genus Plateumaris (which was wrong) and nor for the subgenera Juliusina and Plateumaris s. str (which is true). Subsequently, Chen (1941) designated Donacia affinis Kunze as the type species for Plateumaris, but this was overlooked by Monrós (1959) who designated Donacia geniculata Thomson (= Donacia discolor Panzer) as the type species for Plateumaris s. str. and Prionus bracatus Scopoli for Juliusina Reitter. Iablokoff-Khnzorian (1966) suggested the name Euplateumaris for the subgenus Plateumaris s. str. established by Reitter, with Donacia sericea (L.) as type species. He also re-established D. nigra F. (= bracata) as type species of the genus Plateumaris, apparently unaware of both designations by Monrós (1959) and Chen (1941), and therefore placed Juliusina as a junior synonym of Plateumaris because both were named based on the same nominal taxon. Jolivet (1970) followed the designation of Iablokoff-Khnzorian (1966) but Mann and Crowson (1983) accepted Monrós' designations and advocated acceptance of Plateumaris s. str (= Euplateumaris) and Plateumaris (Juliusina) as the correct subgeneric classifications of Plateumaris. Lopatin (1984) correctly cited P. bracata as type species of Plateumaris but he assigned this species to Plateumaris (Juliusina).
The names Plateumaris Thomson, 1859 andJuliusina Reitter, 1920 are based on the same type species (Prionus bracatus) which makes the subgenus Juliusina a synonym of Plateumaris in the sense of the whole genus, which was endorsed by Warchałowski (2010). This synopsis of the type species designations and the use of the names as described was elaborated in detail by Askevold (1991). Also, he was the first who attempted to assess the validity of Plateumaris as a genus and the validity of the two subgenera.
Taxonomic status of Plateumaris. Most European authors accepted the genus Plateumaris, but North American authors were reluctant and oscillated between the use of this name at generic and subgeneric ranks within the genus Donacia. This ambiguity led to confusion about the genus name Plateumaris, worsening the existing confusion over the name Plateumaris of the Palaearctic species (see above). Askevold (1990) understood that Plateumaris was monophyletic, defined by the synapomorphy of the ovipositor structure, and that Plateumaris was the sister group to all other Donaciinae, and his morphologically based conclusions were confirmed by several independent molecular analyses Kölsch and Pedersen 2008;Sota et al. 2008;Hayashi and Sota 2014;Reis et al. 2020).
Previous subgeneric classifications. Askevold (1990Askevold ( , 1991 concluded that the division into two subgenera by Reitter (1920) did not reflect the phylogenetic reality. The two subgenera were erected based on characters that do not occur in all members assigned to them or they were based on plesiomorphic characters. Notably, neither subgenus can be characterised by a synapomorphy. His conclusion that Euplateumaris and Juliusina cannot be regarded as subgenera has also been confirmed by molecular studies (Kölsch and Pedersen 2008;Sota et al. 2008). Therefore, this paper does not deal with the confusion over subgeneric names and various designated type species.
In central Europe, the widely used key of Mohr (1966a) separated Plateumaris into two subgenera. The short note in the updated key by Kippenberg (1994: 22), "The separation into the subgenera Juliusina Rtt. and Plateumaris s. str. is not tenable," did not prevent coleopterologists from using the subgeneric names in their collections or publications, and even on a Palaearctic scale, the subgeneric names Euplateumaris and Juliusina were still used by Silfverberg (2010) and Bieńkowski (2014). Possibly the title 'Classification, Reconstructed Phylogeny, and Geographic History of the New World Members of Plateumaris Thomson, 1859' of Askevold (1991 suggested that this publication dealt only with new world Plateumaris species and did not contain relevant information on Palaearctic Plateumaris species or their subgeneric statuses. Diagnosis of the genus Plateumaris Thomson, 1959. Askevold (1991) detailed the diagnosis so only the most necessary characters needed to distinguish the Plateumaris species from all other Donaciinae are listed below: • Sutural margin of elytron explanate apically, sutural interval sinuates distinctly before apex, lower sutural margin broadly exposed (Fig. 1A); • Elytral apex rounded, inner angle sharp, no outer angle protruding; • First abdominal segment as long as the others combined; • Host plants are typically Cyperaceae, but also a few other wetland plants.
The aedeagus of Plateumaris species and some other representatives of the Donaciinae consists of a median lobe which contains the endophallus and the lateral parameres (Fig. 1B). The parameres are fused basally and distally, forming a ring around the median lobe. This parameric structure is the tegmen, composed of a ventral strut and a dorsal cap (for more details and functional descriptions see Askevold 1991 andHayashi 2020). The frontal view towards the apex of the median lobe and of the cap of tegmen are usually very characteristic of each Plateumaris species and therefore suitable to distinguish them in most cases. Some species can be distinguished only by subtle morphological characters of their endophallus. Biology. Reed beetles live on plants in wetlands. The larvae develop attached to the roots in the sediment and live as sap suckers gnawing a hole into the root. They breathe by tapping the aerenchyma of the plant using two hollow abdominal hooks, which are connected to their tracheal system; therefore, they can live even in anoxic mud (Böving 1910). Adults remain mostly above the surface sitting on aquatic plants but are able to hide under water while the ventral hairs serve as plastron respiration (Rheinheimer and Hassler 2018). The larvae pupate at the end of their second summer in a cocoon, attached to the root of the food plant. The beetle overwinters in an air-filled cocoon and emerges the following spring. In warmer climates the larvae may pupate after their first summer (Böving 1910;Kleinschmidt and Kölsch 2011).
The larval host plants are mostly members of Cyperaceae, but include some Juncaceae and Poaceae (e.g., Phragmites australis (Cav.) Trin. ex Steud.). Acorus calamus L. (Araceae), Caltha palustris L. (Ranunculaceae), and lris versicolor L. (Iridaceae) are also mentioned as food plants (Borowiec 1984;Bieńkowski 2014). Most species are mono-or oligophagous, especially the larvae. Adult beetles feed on the leaves, although some species are pollen feeders, and some may also feed on petals. If a larva is attached to the root of a plant and gnawing traces are found, we can be sure that this is a host plant for this species. Adults may use a slightly broader range of plants. Several species feeding on pollen use the plants of their habitat. Therefore, adults can be observed on wetland plants that are mostly not larval food plants. The adults are active mainly in spring and early summer, sometimes also in autumn. No specific phenology data are provided here for the species because many have a wide distribution range and the time of "spring" differs between the populations within the Palearctic region.
Plateumaris species prefer habitats of wet sedge meadows, peat bogs, and fens, in contrast to Donacia species which live on aquatic plants with emerging parts and in contrast to Macroplea species which live on totally submerged aquatic plants.
Historical biogeography. Plateumaris species are found only in the Holarctic region with ten species in the Palaearctic and 17 species in the Nearctic (Askevold 1991); the latter occur mainly in Canada and the northern states of the USA. These two subregions have neither a Plateumaris species nor any other Donaciinae species in common, although molecular analysis shows that many Palaearctic Plateumaris species are more closely related to Nearctic species than to other Palaearctic species (Askevold 1991;Hayashi 2020). Dispersal vicariance analysis and divergence time estimation revealed that the European and North American-Asian lineages diverged during the Eocene. Moreover, subsequent differentiation occurred repeatedly between North American and Asian species, which was facilitated by three dispersal events from North America to Asia and one in the opposite direction during the late Eocene through the late Miocene (Kölsch and Pedersen 2008;Sota et al. 2008;Hayashi and Sota 2014).
Checklist and distribution. A summary of the distribution of the Plateumaris species in the Palaearctic region is shown in Table 2.
Palaearctic region: Plateumaris sericea has the largest distribution area of any Donaciinae species: it is recorded from Ireland and Great Britain to the whole of continental Europe, North Africa, and almost all Asian countries which belong to the Palaearctic region. Plateumaris weisei occurs from northern Europe to east Asia, from Siberia to northern China, Japan (Hokkaido), and South Korea.
Western Palaearctic region: Three species occur only in Europe and in Asia west of Lake Baikal: P. bracata, P. consimilis, and P. rustica.
Eastern Palaearctic region: Five species occur only in Asia east of Lake Baikal: P. amurensis, P. roscida, and P. shirahatai, and two species are endemic to the Japanese archipelago, P. akiensis and P. constricticollis. Taxonomic history. Because this species was not described until 1984 it is possible that some small Plateumaris specimens from Japan are misidentified as another species in old collections.
Diagnosis. Habitus ( Fig. 2A) like a typical Plateumaris, but with conspicuously short elytra and legs, elytra length is at the most 1.6× longer than wide, colour black or bronze-metallic, also with a bluish or greenish lustre, elytra shiny, antennomeres thicker than in most Plateumaris species, legs reddish but femora dark.
Description. There are comprehensive descriptions in Tominaga and Katsura (1984) and in Hayashi (2020) with many detailed figures so the description below is confined to the essentials.
Size: 6.4-7.6 mm. Colour: Colour of pronotum and elytra entirely metallic black or reddish coppery, some specimens with a bluish or greenish lustre.
Pronotum: Slightly longer than wide, outline more or less cordate, gradually narrowed backwards with anterior margin strongly produced forward; dorsal surface with feebly raised anterior and posterior tubercles, disc densely but finely punctate, median line shallow, with a conspicuous broad collar along the posterior margin.
Elytra: Robust and short, 1.6× as long as wide, with arched outer margin, rows of punctures regular, their interstices smooth, usually sparsely but sometimes densely punctate.
Legs: Legs short, reddish brown, partly dark rufous or black, especially the apical half of the femora, metafemur robust in shape, with a tooth; T2 shorter than its width, T1 > T2 < T3.
Aedeagus: See Fig. 2B, C. Similar species. Plateumaris akiensis looks similar to P. constricticollis but can be identified by its shorter elytra. In P. constricticollis the elytral length is distinctly > 1.6× longer than wide.
Biology. The adults feed on pollen of Carex sp. and Scirpus juncoides (Hayashi 2020). Narita (2003) described the larvae from Carex otaruensis Franch. Scirpus sp. is also thought to be a larval host plant (Hayashi 2020).
Distribution. Endemic species found in Honshu, Japan. The only records so far are from Hiroshima and Shimane prefectures in south-west Honshu.
Material examined. Five specimens from Hiroshima prefecture, stored in BMNH, HNHM, and NMPC. Type material. Types could not be located so far. In his original description (translation in Geiser and Geiser 2023), Weise gave no indication from whom he received the material, where the type is stored, nor the number of specimens he studied.

Plateumaris amurensis Weise, 1898
Taxonomic history and synonymies. Weise (1898) assumed a relationship to P. discolor and further compared it with P. weisei that is similar in colour. Reitter (1920) mentioned both P. amurensis and P. weisei in a footnote with some characters from their original descriptions but not in his identification key. He also noted no distinguishing characters. Both species are also mentioned in the catalogue of Winkler (1930). Goecke (1937) regarded P. amurensis as synonymous with P. weisei in his modification to Reitter's (1920) identification key, but he provided no reason or reference for this synonymy and subsequently, P. amurensis was considered a synonym (Goecke 1960;Jolivet 1970). Askevold (1991) agreed with Goecke's view. Only in the key of Gressitt and Kimoto (1961) is P. amurensis regarded as a species propria with different characters to P. mongolica (which is now a synonym of P. weisei) but those characters are not adequate to distinguish these two species. Medvedev (1992) regarded P. amurensis a valid species;  then confirmed that P. amurensis was a species propria. Many external characters are highly variable and sometimes overlap with the characters of P. weisei. Due to the situation described above, specimens of P. amurensis are sometimes hidden in collections because they were identified as P. weisei.
Diagnosis. Metafemur with a prominent, blade-like tooth, apical part of median lobe of aedeagus gradually narrowed towards the apex.
Pygidium: Apex pubescent, shallowly emarginate or sometimes truncate in male and rounded in female. Last sternite entirely coppery but apex at middle part rufous, apical shape variable in male, acute in female (Table 3). Ovipositor: Elongate, both sides paralleled, apical angle acute, subapical corner with teeth, apex remarkably prominent (Table 3).
Aedeagus: With median lobe, acute but slightly rounded at the apex; cap of tegmen gradually narrowed distally, notched, or sometimes rounded at apex ( Fig. 3C-E). Similar species. The most similar species is Plateumaris weisei and the main distinguishing characters are shown in Table 3. Otherwise, the East Palaearctic Plateumaris species are not easy to distinguish. I found specimens of P. amurensis in museums also identified as P. roscida, P. sericea, or as their synonyms.
Biology. Host plant and larvae are unknown. Distribution. East Palaearctic only. Records exist for Asia: Russia: Transbaikalia, Republic of Sakha (Yakutia): southern part of river Lena; Amur Oblast, Khabarovsk Krai, Primorsky Krai, Sakhalin, Kurile Islands. Sometimes P. amurensis is mentioned from Japan (e.g., Bieńkowski 2014) but these are erroneous records caused by confusion with P. weisei (Hayashi , 2020 Type locality. Plateumaris bracatus: Carniola, a historical region which comprised parts of present-day Slovenia. Type material. Type specimens of P. bracatus do not exist anymore. Sadly, Scopoli's collection of insects from Carniola decayed during his life time. He committed this collection to a printer in Vienna who apparently did not store it adequately. Before all the pictures were printed, Scopoli complained in his 1773 letter to Linnaeus (Brelih et al. 2006) that the insects "had either decayed or fallen apart".
Taxonomic history and synonymies. In nearly all publications the species name has been misspelled "braccata". The spelling in the original description by Scopoli (1772) is "Prionus Bracatus" with a single "c" (Geiser and Geiser 2023). Scopoli used this epithet presumably because "bracae" means "trousers" or "pants" referring to the clubbed shape of the metafemora. A variant of this word exists in later medieval Latin and was spelled "braccae", which Schenkling (1917) used in his explanation of the scientific names of beetles. Because the spelling of the original description is linguistically correct it must be preserved unaltered (ICZN, Art. 32.2.1). Because the original description by Scopoli is very short, Weise (1893) published a more detailed redescription (see Geiser and Geiser 2023).
Donacia abdominalis (Olivier, 1800): Silfverberg (2010) cited this synonym as abdominalis (Olivier, 1795). Despite the title page dated 1795, the fourth volume of Olivier's 'Entomologie, ou histoire naturelle des insectes' was issued in two parts, one probably in 1795 and the second one in 1800. All new taxa made available in this work have previously been dated 1795 in the literature (Bousquet 2018). In any case, Olivier's volume does not contain the original description. He also listed another name of this species, Leptura violacea Pallas, and then described the typical characters of P. bracata. Later, P. abdominalis was regarded synonymous with P. rustica because it was mixed up with P. abdominalis Bedel, 1891, who intentionally did not describe it as a new species (see section on P. rustica for details).
Plateumaris fairmairi was first described by LeGrand (1861a) on page 265 as variation of Donacia nigra (see Geiser and Geiser 2023) from a specimen with complete black antennae and legs. The often-mentioned page 89 derives from the reprint (LeGrand 1861b).
Fabricius described Donacia nigra by 1792 (see Geiser and Geiser 2023). He allocated it close to D. festucae which is now synonymous with P. sericea. The name Plateumaris was not established then, but Fabricius (1792) noticed some differences from other Donacia species.
Diagnosis. This is the largest Plateumaris species, body length: 8.0-12.0 mm (Fig. 4A). Head, pronotum and elytra entirely black or with a weak blue, purple or green metallic lustre, antennae and legs reddish brown in most specimens, elytra elongate, ~ 2× as long as wide, side contour of the elytra very straight, almost parallel.
Description. Size: 8.0-12.0 mm. Colour: Dark, entirely black or at the most with weak blue, purple or green metallic lustre.
Pronotum: Cordate, ahead distinctly wider than behind, anterior tubercles only slightly convex, slightly pubescent. Disc with fine punctures, median line well developed, sometimes shortened, but also very shallow and almost invisible in some specimens.
Legs: Colour variation from complete reddish brown to dark apical parts and completely dark legs, femora basally very broad, metafemur with broad tooth, robust in male, in female feeble or indistinct.
Aedeagus: see Fig. 4B. Similar species. The most similar species is Plateumaris consimilis, which is smaller (6.0-9.2 mm) on average, its elytra are shorter with a ratio of length to width ≤ 1.8, and the outer contour of the elytra are slightly rounded, not parallel.
Biology. Plateumaris bracata is monophagous on Phragmites australis (Cav.) Trin. ex Steud., the common reed, Poaceae (Bieńkowski 2014). The beetle can be found concealed in the Phragmites leaf-folds. When feeding, it penetrates the young leaf shoots which later unfold to present a characteristic transverse series of round holes. Donacia clavipes feeds on the same plant species in a similar fashion but, in this case, the series of holes produced are irregularly elongated (Menzies and Cox 1996;Rheinheimer and Hassler 2018). For identification of the larvae see Steinhausen (1994) and Bieńkowski and Orlova-Bieńkowskaja (2004). Despite its large distribution area and its common food plant, its number of specimens stored in museum collections is always remarkably fewer than the number of P. consimilis or P. sericea. Compared with Donacia clavipes, which occurs on the same food plant, the numbers of P. bracata specimens are also much fewer. Recent records are extremely rare.
Distribution.  Balthasar, 1934: 128 [syn. nov.]. Donacia variabilis Kunze, 1818: 39. Plateumaris consimilis f. violacea Bechyné, 1942: 234, 236 [infrasubspecific name]. Plateumaris consimilis f. viridis Bechyné, 1942: 234, 236 Type locality. Plateumaris consimilis: unknown, but possibly in Austria (the country in 1781 was much larger than today) because the original description is in a book titled 'Enumeratio insectorum Austriae indigenorum'. Type material. Holotype or type series of P. consimilis unknown. Taxonomic history and synonymies. Bechyne (1942) detailed statistics about the different colours and subtle structures on the pronotum of P. consimilis, but without convincing results. He named colour variations as "forma" but conceded that there also existed combinations of colours in between. These names are indicated above for the sake of completeness, but they are irrelevant to systematics.
Schrank de Paula (1781: 155) described Leptura consimilis with bronze and black-golden colouration. On the next page of this publication, he described a new species Leptura assimilis. The difference from the former species is indicated as "black" and the elytra with nine rows of punctures in contrast to those of P. consimilis which he described with ten rows of punctures [both species have elytra with 11 rows of punctures]. In that pioneer period, this species common in central Europe was also described as Donacia rufipes by Olivier (1791), Donacia discolor by Hoppe (1795), and Donacia variabilis by Kunze (1818), who already mentioned the great variability of this species by its specific name.
Donacia discolor was described by Hoppe (1795). According to Bousquet (2016) this was published on [30] April 1795, but a description of a Donacia discolor had been already published by Panzer on 14 February 1795 (Bousquet 2016). Therefore, Donacia discolor Hoppe was immediately a homonym. Later, both species were assigned to Plateumaris, therefore D. discolor Hoppe remained a homonym.
Plateumaris consimilis orientalis was described by Shavrov (1948) (see Geiser and Geiser 2023), which he thought to represent a subspecies of P. consimilis, but it resulted in being synonymous with P. weisei (see at P. weisei below for further explanation).
Diagnosis. Pronotum cordate, anterior tubercles slightly convex. Upper side with metallic lustre in varying colours, antennae, and legs at least partly reddish brown. Elytra 1.5-1.8× longer than wide.
Pronotum: cordate, ahead wider than behind, anterior tubercles only slightly convex, disc uniformly punctate, median line obsolete to fine but distinct.
Elytra: 1.5-1.8× longer than wide, never twice as long as wide, side contours slightly convex, not parallel, elytra rugose and punctulate.
Legs: Colour variation from completely reddish brown to only reddish at the joints, femora basally very broad, metafemora with sharp or broad tooth. Aedeagus: The shape varies between the short, more rounded form in P. bracata and the elongated acute form of P. rustica (Fig. 5C, D).
The most similar species are Plateumaris bracata and P. rustica: P. bracata has longer elytra, ~ 2× as long as wide and the side contour of the elytra is parallel, not convex (Fig. 4C). Plateumaris rustica has the pronotum not cordate, and disk and tubercles flattened (Fig. 10A). Plateumaris weisei could be mistaken for P. consimilis but their distribution areas hardly overlap.
Biology. Although P. consimilis is one of the common Plateumaris species, its larva was not described until 2014 by Medvedev and Muravitsky. The larvae and adults feed on Carex sp. (Cyperaceae). Also, Juncus articulatus (Juncaceae) and Caltha sp. (Ranunculaceae) are mentioned as food plants of adults, on which they feed on the pollen (Rheinheimer and Hassler 2018). Plateumaris consimilis lives in wetlands, fens, near springs, and moor grass meadows. It is more frequent on low calcareous soils, where it is usually the only species of Donaciinae. It is site-loyal and cannot be caught in pitfall traps (with rare exceptions) (Krause 1982 Remarks. Plateumaris consimilis does not occur in the East Palaearctic which has also been confirmed recently by Hayashi (2020). Records from Far East and Japan, e.g., in Goecke (1960) or Warchałowski (2010), are due to records of "Plateumaris consimilis orientalis Shavrov, 1948" which is synonymous with P. weisei (see below). Note that specimens of P. weisei misidentified as P. consimilis were found in collections (pers. obs.).
Material examined. More than 200 specimens from different localities throughout the distribution area. Balthasar, 1934, syn. nov.  Remarks. Balthasar (1934) described a species Plateumaris tenuicornis from one P. consimilis specimen collected in Bosnia, which he studied in the collection of the Slovak National Museum, Bratislava. The sketches where he compared the pronotum of both species are provided in Fig. 6C, D. Bechyné (1942) published an article about this description. He studied 335 specimens of P. consimilis, mostly from the area which belongs now to the Czech Republic, but also from central France and Podolia, a historic region in Eastern Europe located in the west-central and south-western parts of Ukraine and north-eastern Moldova, but he did not study the holotype of P. tenuicornis (possibly due to the political situation in Europe at that time). He meticulously worked out that all described characters of P. tenuicornis were within the variation range of the characters of P. consimilis. Bechyné published this article in Czech and Latin in a Czech journal, which has been ignored by most Donaciinae specialists. The English translation of the Latin text is now available in Geiser and Geiser (2023). Askevold (1991) knew neither of the article of Bechyné (1942) nor of the holotype of P. tenuicornis, but he studied the description of Balthasar (1934) and concluded "All character states used by Balthasar are ones that I have also found among P. consimilis" and then declared P. tenuicornis as a probable new synonym. I studied the holotype of P. tenuicornis still stored in the Slovak National Museum in Bratislava (Fig. 6A, B) and I can confirm that Bechyné and Askevold were correct in every detail.

Plateumaris tenuicornis
Because Bechyné only indirectly treated P. tenuicornis as a synonym, and because Askevold only suggested that P. tenuicornis should be considered as a probable new synonym, I determined that P. tenuicornis Balthasar, 1934 is a new synonym of P. consimilis (Schrank, 1781) according to Bechyné (1942), supposed by Askevold (1991), and now confirmed based on a study of the type material and original descriptions. ( Taxonomic history and synonymies. Jacoby (1885) described this Plateumaris species as Donacia constricticollis. The details of the location and the date are not tagged to the holotype, and the label contains only "Japan G. Lewis, BMNH 1910-320". Bates (1883) published the itinerary of G. Lewis' journey through Japan from February 1880 to September 1881 that contains the exact data. The type specimen was collected at Lake Junsai near Hakodate in south Hokkaido where Lewis sojourned 28-30 July 1880.

Plateumaris constricticollis
Lays (2002) refers to a female type specimen: 1 ♀, "Type", "Donacia constricticollis Jac." [no further label data, origin unknown], stored in RBINS. It is unlikely that this "type" specimen could be a paratype or allotype of the series collected in Hokkaido at the same site as the holotype. According to Lays (2002) this specimen belongs to the subspecies P. constricticollis babai, which occurs only in central Honshu. One must keep in mind that some decades ago "type" labels were sometimes added later to specimens in several museum collections without thorough studies.
Specimens of P. constricticollis reveal a remarkable variation in body size and colouration, pronotal disc, and even genital structures. This resulted in the description of four subspecies. Further studies concluded that there were two subspecies in addition to the nominate species, and therefore the other two subspecies names are synonyms (Hayashi and Shiyake 2004). This is also confirmed by several molecular studies Sota et al. 2008;Hayashi and Sota 2014). However, the morphological discrimination of these subspecies is very difficult because of the variations in some key characters.
Diagnosis. The characters common to all subspecies are the following: surface very shiny (Fig. 7), dorsal colouration variable, bronze brown or dark cupreous, black, blue, or green, pronotum cordate, slightly longer than broad, anterior tubercles prominent, elytra regularly and strongly punctate, metafemora with blade-like tooth. It looks similar to a glossy P. consimilis that does not occur in the East Palaearctic region.
Description. Size: 6.6-11.9 mm. Plateumaris constricticollis and its subspecies have been thoroughly studied by Japanese colleagues, with detailed descriptions of their morphological characters and their variations, as well as phylogeny, biogeographical history, biology, and molecular analyses (Tominaga and Katsura 1984;Hayashi 2002Hayashi , 2020Hayashi and Shiyake 2004;Hayashi and Sota 2014). The three subspecies and their distinguishing characters are described in the section "Identification Key".
The similar species Plateumaris weisei is not shiny or glossy, its pronotum not cordate, and the legs are longer and slenderer.
Biology.  analysed the geographic variation in body size and ovipositor dimensions in three subspecies in different climatic conditions and on different host plants, and reported a significant correlation of the body size and ovipositor size with snow depth. The larvae feed on Carex sp. (Cyperaceae) (Narita 2003). Cocoons of P. c. babai were also found on roots of Phragmites australis (Poaceae), Carex thunbergia, and Carex ampliata. Eleocharis sp. is recorded as a larval host plant for P. c. toyamensis .
Material examined. Approximately 60 specimens from Japan. No location label is tagged to the holotype, but the type locality "Tschita" is indicated in the original description by Weise (1912). The holotype was examined in May 2023.
Taxonomic history and synonymies. Weise (1912) described Plateumaris roscida (see Geiser and Geiser 2023) based on a specimen from Tschita. He obtained it from Johann Nepomuk Ertl (1860-1925, Munich, Germany), a dedicated beetle collector who had connections to missionaries. This specimen was presumably collected during a journey to China. Reitter (1920) published an identification key for Palaearctic Donaciinae. In a footnote to P. sericea he described P. annularis from Russia, Far East, Amur region, Chabarowsk (krai), Nikolajewsk, coll. Koltze (see Geiser and Geiser 2023). Reitter did not mention in the description that this P. annularis is armed with a prominent metafemoral tooth, but he provided this information indirectly two paragraphs later when he contemplated if P. obsoleta could be the same species as P. annularis. He also described that, in contrast, P. obsoleta has completely dark legs and the posterior femora are practically unarmed, or only bluntly angled. This description and further notes in Reitter (1920) match completely with the characters of P. roscida. Kolossow (1930: 29) synonymised P. annularis with P. roscida with the laconic line "Plateumaris annularis Reitt. (1920) = Pl. roscida Weise (1912)". Goecke (1957a) studied a specimen from ZSM, labelled "Samml. Ertl" [= collection of Ertl] and "Pl. roscida n. sp. Wse" in the handwriting of Weise. He also examined four specimens from the then "Deutsches Entomologisches Institut Berlin" (now SDEI) labelled "Pl. annularis Reitter", one of them labelled "Nikolajewsk, Graeser" and "Pl. annularis Rtr., Chabaroska, Weise" and another two specimens labelled "Pl. annularis" without location labels. All four specimens were labelled as "Type". He then compared the P. roscida specimen with the P. annularis specimens and confirmed the statement of Kolossow (1930) that they all belong to P. roscida. Askevold (1991) studied other specimens from Russia and north China identified as P. annularis and confirmed that they belonged unambiguously to P. roscida. He also suggested that P. caucasica may be synonym of P. roscida because of the description of Zaitzev (1930), but he conceded that the geographic distance between the Caucasus and Transbaikalia caused a problem.
Diagnosis. Upper side bronze, bluish, or purplish, flat-lustrous, habitus similar to P. sericea, antennomeres reddish basally and darkened apically, pronotum with flattened anterior tubercles, femora reddish on basal half and dark on apical half. Aedeagus with a conspicuous elongated peak.
Pronotum: Almost quadratic or slightly longer than wide, anterior tubercles flattened, disc coarsely and closely punctate with fine wrinkles, median groove narrow or indistinct, in posterior part short and slightly deeper, then forked into two horizontal grooves near the bottom line.
Legs: In most specimens the femora are reddish on basal half and dark metallic on apical half, tibia reddish with dark parts, tarsomeres dark or with reddish basal part. Some specimens with entirely reddish legs. Metafemora with prominent, thorn-shaped tooth in most specimens.
Pygidium of females with an apical notch, males broadly emarginate. Aedeagus: Median lobe with a conspicuous elongated peak, cap of tegmen with a deep apical notch (Fig. 9).
Two similar species are Plateumaris sericea and P. shirahatai which differ: in P. roscida the pronotum and its tubercles are flattened, legs with large reddish parts, and the aedeagus has a conspicuous elongated peak.
Type material. Type specimens missing. Taxonomic history and synonymies. Kunze (1818) described four new Donacia species (see original text and translation in Geiser and Geiser 2023) which in fact belong to one single Plateumaris species (Askevold 1991 in part). The name Donacia rustica was described first in this publication, so planicollis, pallipes, and affinis are now synonyms.
Some authors, like Jolivet (1970) and Borowiec (1984), cited the authority of P. rustica as Schüppel (1818, in Kunze 1818) but this is inaccurate since Kunze (1818) wrote after the description: "D. rustica Schüppel in litt." Therefore, the suggestion is there that the name is derived from J. Schüppel (Berlin), but Kunze actually described this species and published it. The unambiguous authority of P. rustica is Kunze; therefore, D. rustica (Schüppel, 1818) is a nomen nudum. Note that there is no publication of "Schüppel (1818)".
The names P. abdominalis Bedel, 1891 and P. (Donacia) abdominalis Olivier, 1795 [1800 is correct, see above for P. bracata] were erroneously attributed to P. rustica. The name P. abdominalis is frequently mentioned as a synonym for P. rustica or P. affinis as occurs in the key by Jacobson (1892): "abdominalis Oliv." with P. affinis as its synonym. Clavareau (1913) defined "abdominalis Bedel" as synonymous with P. affinis and this was followed by Reitter (1920), Winkler (1930), Goecke (1960), and Jolivet (1970); the latter also mentioned "abdominalis Olivier" as synonymous with P. bracata, but Olivier did not describe it [see above for P. bracata]. Also, Bedel (1891) did not describe P. abdominalis; in his list of the Coleoptera of the Seine basin he mentioned P. abdominalis Olivier, together with the synonyms affinis Kunze, 1818 and [sic!] fusca Zschach, 1788 (synonymous with P. bracata). Therefore, P. abdominalis Bedel is a nomen nudum, a misidentification or misinterpretation by Bedel, but not a synonym of P. affinis. Donacia affinis was also described in Kunze (1818) (see Geiser and Geiser 2023). Goecke (1943) suggested that P. affinis should be considered synonymous with P. rustica. Askevold (1991: 37) synonymised it after examination of ~ 250 specimens from various locations in Europe. These beetles are typically separated in keys by the colour of the antennae, legs, and ventral side, and by the metafemoral tooth size, but these are highly variable characters among many Donaciinae (pers. obs.). In fact, the aedeagi of these two "species" are indistinguishable.
Plateumaris pallipes was assigned as a synonym of P. affinis and P. planicollis as a synonym of P. rustica. As the original descriptions of Kunze (1818) show, all characters are within the variation range of the typical characters of P. rustica (Geiser and Geiser 2023).
Plateumaris picipes was described by Weise (1898) as a variation (Geiser and Geiser 2023). It refers to specimens with at least very dark femora up to very dark legs. Albeit the basal joints of the femora are always reddish.

Diagnosis.
Upper side mostly metallic, antennae and legs entirely or partly reddish brown. It has a very smooth and the most flattened pronotum of all Palaearctic Plateumaris species (Fig. 10A).
Description. Size: 6.5-9.0 mm. Colour: Upper side bronze or black with greenish, bluish, or purplish metallic lustre, colour of pronotum and elytra mostly the same but can also differ significantly. Antennae and legs entirely or partly reddish brown.
Pronotum: Almost quadratic, only at the basis slightly constricted, with flat disc and indistinct anterior tubercles; surface shiny or alutaceous, disc smooth with small shallow dots, more or less densely dotted, median line varies from imperceptible to distinctive.
Legs: Yellow reddish, sometimes partly or almost entirely darkened, piceous, but always with reddish joints (var. picipes Weise, 1898). Femora basally broad, metafemoral tooth very variable, mostly prominent, in some (mostly female) Figure 10. Plateumaris rustica A habitus B median lobe (photographs by K. Matsumoto). Scale bar: one unit -1 mm. specimens very small or imperceptible. There is no geographic correlation concerning the size of the tooth.
Aedeagus: Median lobe distinctly elongated, apex acute (Fig. 10B). There are two similar species. Plateumaris consimilis has the pronotum distinctly cordate and the disc is not flattened. The pronotum of P. weisei is trapeziform and slightly longer than wide. In the territories where their distribution areas are overlapping (European part of Russia) it can be distinguished from P. weisei by the quadratic shape of the pronotum.
Also, the aedeagi of these species are clearly different (compare Fig. 10B with Fig. 17B, C, E).
Biology. The larvae are oligophagous on Carex sp. and other Cyperaceae. Adults feed on leaves and stems, not on pollen (Rheinheimer and Hassler 2018). For identification of the larvae see Steinhausen (1994) and Bieńkowski and Orlova-Bieńkowskaja (2004). Although P. rustica is widespread in the West Palaearctic region and there are many of its food plants available, it is rather rare suggesting that it needs not only wetland with Cyperaceae but also additional ecological conditions.  (Ekiz et al. 2020). Remarks: Plateumaris rustica was unknown from Turkey. There was no record in the "Checklist of leaf beetles of Turkey" (Ekiz et al. 2013). In 2019 I identified 12 specimens from Bolu province stored in Verona (MSNV) and their detailed data are published in Ekiz et al. (2020), including the type location of P. sulcifrons in Kahramanmaraş province. In 2021 I found 25 specimens in the coll. Voříšek which is now stored in BMNH. These specimens were labelled as "P. sulcifrons Weise J. Voříšek det." but are now relabelled as P. rustica. Also, the aedeagi of these "P. sulcifrons" were identical with the aedeagus of P. rustica.
Material studied. More than 200 specimens throughout the West Palaearctic region. Remarks. Askevold (1991) declared P. sulcifrons as a "probable new synonymy" for P. rustica. The holotype (♀) is missing but the analysis of the elaborate original description (see Geiser and Geiser 2023) indicates that the characters of P. sulcifrons are within the variation range of P. rustica characters (Table 4). Weise indicates a range of [body] length: 8-9 mm and colour variation in the antennae and legs. This suggests that he had examined more than one (female) specimen. Since 1900 the name P. sulcifrons is mentioned in almost all catalogues and identification keys for the (West) Palaearctic, but no new records were published.

Plateumaris sulcifrons
Besides, there was a confusion about the locus typicus. Weise (1900) published only: "Zeitun (Staudinger)". This sparse note of the collection site led to misinterpretations: "Zeitun" is correctly assigned to Asia Minor (Reitter 1920;Winkler 1930), but it was misinterpreted by Goecke (1960) as "Żejtun", a town in the east of Malta. Henceforward it was mentioned as a species from Malta (Jolivet 1970;Borowiec 1984;Askevold 1991;Silfverberg 2010;Warchałowski 2010). This location error confirmed the opinion that P. sulcifrons is probably endemic to Malta, therefore missing further records were less suspect.
Otto Staudinger (1830-1900) was a German entomologist who went on numerous collecting trips or promoted them, but insects were not collected in Malta, neither on his own journeys nor on his commissioned trips. In 1872 he visited the Cilician Taurus (Anonymous 1901;Wikipedia [05.10.2022]). Therefore, "Zeitun" mentioned in Weise (1900) is actually "Zeytun" district (now Süleymanlı) of today's Kahramanmaraş province of Turkey (Ekiz et al. 2020). Different spellings and change of geographical names also did not help to clarify this case.
Unfortunately, the first description does not indicate where these specimens are stored. It is unlikely that Weise returned the type(s) to Staudinger, who was then working on his Lepidoptera Catalogues in his last years. Weise's private collection and especially the Chrysomelidae part are stored in the Museum für Naturkunde in Berlin (ZMHB), but no Plateumaris specimen labelled "sulcifrons" could be found there, despite the search by J. Frisch in 2019. I screened the Plateumaris collection in 2023 but found no specimen that could be considered the type.
Like other species, where only the type specimen is known, P. sulcifrons was suspected to be a synonym of a well-known species. Weise wrote that it is similar to P. rustica and P. affinis. Askevold (1991) synonymised P. affinis with P. rustica. He noticed that the characters Weise mentioned are typical for P. rustica and suggested that P. sulcifrons may be conspecific. Warchałowski (2003) treated P. sulcifrons also as synonym to P. rustica in his key of the Chrysomelidae of the Europe and the Mediterranean area. However, he treated it as valid species, although doubtful, in his key of the Chrysomelidae of the Palaearctic region (Warchałowski 2010). In Silfverberg (2010) it was listed as valid species from Malta. The locus typicus was corrected to Turkey in Löbl and Smetana (2013).
Unfortunately, I could not examine the type specimen. To confirm the arguments of Askevold (1991) with more details, the characters mentioned by Weise (1900) are compared with the characters of P. rustica in Table 4. Table 4. Comparison of the characters of Plateumaris sulcifrons (as described by Weise 1900) and the corresponding characters of P. rustica (by EG).

Characters of P. rustica with comments
Length: 8-9 mm Length of P. rustica: 6.5-9.0 Description based on female specimens Females are usually larger than males in Plateumaris species, therefore 8-9 mm matches very well

Slightly convex Same as P. rustica
Upper side bronze-coloured, below jet-black, silky grey The same colours occur in some specimens of P. rustica Antennae, tibiae and tarsomeres dark reddish Same as P. rustica

Frons with a wide and deep groove
In P. rustica frons with deep or shallow groove, narrow or broad, longitudinal calli of every side of the groove distinctive or flattened Prothorax square, very finely pubescent, very slightly constricted before the base, disc almost flat, shiny, rather densely punctured, middle groove anterior and posterior deepened impressed, the tubercles on both sides almost imperceptible, slightly smooth These are typical characters of a pronotum of P. rustica, the median groove varies from imperceptible to distinctive Elytra with dotted stripes, interstices narrow Same as P. rustica

Femora unarmed
Tooth of metafemur mostly prominent, in some female [sic!] specimens very small or imperceptible Similar to P. rustica and P. affinis but more elongated Without type specimens it is impossible to estimate what means "more elongated" as the ratio length to width varies in specimens of P. rustica The characters which should distinguish P. sulcifrons from P. rustica are either the same or within the variation range of P. rustica. Therefore P. sulcifrons is a synonym of P. rustica. This was also mentioned in Ekiz et al. (2020) and in Geiser and Bezděk (in press), but without the reason provided here.
(most) identification keys P. sericea is characterised by "antennae and legs entirely metallic", which is usually correct. Only in recent keys it is mentioned that there can also be reddish parts at some joints. Therefore, these "not entirely metallic" specimens supported the idea that specimens with a reddish spot belong to a different species or at least subspecies. I examined many specimens from the whole distribution area and determined their morphologic characters inclusive of the aedeagus shape are within the variety range of P. sericea.
In large European collections, where Asian specimens are stored, many of these Asian specimens show a red base of their antennomeres. Perhaps, these specimens were preferentially collected and stored whereas "entirely metallic" specimens were considered as common and not worth keeping.
The genus name Donacia was erected later in 1775 by Fabricius. There he described Donacia crassipes and Donacia simplex and assigned Leptura aquatica L., 1758 to the genus Donacia, but, significantly, he did not change the genus name of Leptura sericea.
Plateumaris discolor kratochvili f. coelicolor was described by Bechyné (1945) based on a series of specimens he collected from Přybyslav (central Bohemia). Therefore, coelicolor is a published but infrasubspecific name.
Plateumaris imitatrix: This name with the author "Apfelbeck" can be found on several museum specimens from Bosnia-Hercegovina (HNHM, coll. Frey in NHMB, SDEI), but a description was never published, therefore P. imitatrix is a nomen nudum. Viktor Apfelbeck (1859Apfelbeck ( -1934 was a former curator of entomology at the National Museum of Bosnia and Herzegovina, Sarajevo. He labelled several specimens from the Balkans with new names which he regarded as new species. Some of them he described later, some of them not. Nevertheless, some of these specimens were also stored in other museums and can be found nowadays. Goecke (1942a) examined one specimen stored in those days in "Deutsches Entomologisches Institut" in Berlin-Dahlem (now SDEI) and identified it as P. sericea unambiguously. I examined three specimens of "P. imitatrix" in HNHM and one in NHMB which are also clearly P. sericea. Presumably, the reddish base of the antennomeres tempted Apfelbeck to regard it as a new species.
Plateumaris intermedia was described by Apfelbeck (1912) on page 239 and not on page 238 in Latin and Serbian (Geiser and Geiser 2023). It was synonymised with P. sericea by Goecke (1942b) who examined a specimen labelled "cotype" from Livanskopolje near Livno (Bosnia) stored in those days in "Deutsches Entomologisches Institut" in Berlin-Dahlem (now SDEI).
Plateumaris discolor kratochvili was described by Bechyné (1945) as a new subspecies in contrast to P. discolor discolor. Both subspecies live in the same habitat. Therefore, they could not be subspecies by definition. The characters to distinguish these two "subspecies" are completely within the variation range of P. sericea. I examined a specimen from Drholec (southern Moravia Czech Republic) leg. et det. Bechyné as P. discolor kratochvoli Beychné, 1945, ex coll. Roubal (SNMC) which is unambiguously P. sericea.
Plateumaris discolor kratochvili forma isocoelicolor, also the forma isocupraria, forma isolacordairei, forma isopurpuricena, and forma isoviolacea were described by Bechyné (1945) based on a series of specimens from Přybyslav (central Bohemia) collected by Bechyné. All these form names are infrasubspecific.
Perris (1864) described Donacia lacordairii based on a specimen from Spain (Geiser and Geiser 2023). He allocated it to the same group ("dans la mème division") as Donacia sericea. It was later regarded as an aberration of P. discolor (Winkler 1930;Balthasar 1934) or as a variation or subspecies P. discolor lacordairii (Silfverberg 2010). Askevold (1991) examined the endophallus of specimens from Spain which are assignable to P. lacordairii. He found it typical for P. sericea from other regions and therefore synonymised it with this species. I examined 31 specimens from BMNH and I agree.
Plateumaris levigata was described by Csiki in 1953 as an aberration of P. sericea.
Plateumaris micans was described as Donacia micans by Panzer in 1795 and not in 1796 according to Alonso-Zarazaga and Evenhuis (2017).
Plateumaris nipponensis was described by Nakane (1963) from Kamikochi, Nagano (Japan). He assigned it closely to P. sericea but listed several relative characters ("more shining", "relatively shorter") which fit easily in the variability of P. sericea. It is regarded as subspecies in Warchałowski (2010) and as a synonym in Hayashi (2020) to P. sericea.
Plateumaris nymphaeae: Fabricius (1792) spelled Donacia nympheae in his original description, but this original spelling was an inadvertent error. According to ICZN 1999 (Art. 32.5.1) it has to be spelled nymphaeae as it was applied in Silfverberg (2010).
Plateumaris palustris was described as Donacia palustris by Schilling in 1838 on page 99 and not in 1837 on page 104. It is a homonym because Herbst (1784) described a Donacia palustris which is now synonymous with P. bracata.
Plateumaris discolor kratochvili forma pseudoviolacea and forma purpuricena were described by Bechyné (1945) based on a series of specimens from Přybyslav (central Bohemia) collected by Bechyné. All these form names are infrasubspecific.
Plateumaris socia was described by Chen (1941) based on three specimens from Chekiang (Zhejiang). In Silfverberg (2010) it is stated as a synonym to P. sericea sibirica. Askevold (1991) considered it a probable new synonym and Hayashi (2020) a synonym of P. sericea. The description of Chen (1941) mentions only characters which are clearly within the variation range of P. sericea, to which this species "is very closely allied". It is also interesting that Gressitt and Kimoto (1961) mentioned in their key of the Chinese species not P. sericea (which occurs in China) but P. socia, separated from the other Chinese Plateumaris species by typical characters of P. sericea.
Plateumaris sericea slovacica Balthasar: In the coll. generalis in SNMC two specimens are stored which are labelled "Čeklís, Slovensko, Plateumaris sericea slovacica det. V. Balthasar, Typus n[ova]. ssp." which I identified as P. sericea. I assume that Vladimir Balthasar (1897Balthasar ( -1978, who described other species and subspecies of Plateumaris (Balthasar 1934) intended to describe these specimens as a new subspecies but never did. Therefore, P. sericea slovacica is a nomen nudum.
Plateumaris discolor ab. tatrica was described by Balthasar (1934) based on one or several specimens (the number is unclear) characterised by a dark purple pronotum and dark violet-blue elytra, collected by Al. Procházka, from Štrbské pleso, High Tatras, Slovakia. Anyway, this is an infrasubspecific name.
General remarks on the morphology and distribution of Plateumaris sericea. Plateumaris sericea has the largest distribution area of all Plateumaris species. It is no surprise that it is also genetically very variable (Hendrich et al. 2015), which is shown also in the variability of the morphological characters. Additionally, to the colour variations mentioned above, P. sericea also varies in the shape and microstructure of the pronotum. While many Donaciinae species can be characterised by a typical shape of the tooth on the metafemur, P. sericea can show no tooth at all, or a very prominent sharp tooth and all shapes in between. Even the aedeagus varies in shape.
Diagnosis. Legs and antennae usually entirely metallic, some specimens with reddish parts near the joints; pygidium of females rounded, in some specimens slightly emarginate, that of males emarginate; apex of median ejaculatory guide rounded.
Description. Size: 6.5-10.5 mm. Colour: Plateumaris sericea shows the greatest colour variety among all Donaciinae species: The whole beetle can be bronze, green, blue, black, cupreous, purple, red, yellow, and all shades in between. Antennae and legs are mostly completely metallic, but there are some specimens with red base of the antennomeres and even with red parts of the legs, usually at the tibiae or tarsomeres.
Pronotum: Outline more or less quadrate, in some specimens longer than wide; anterolateral tubercles prominent but sometimes flattened, the disc varies from alutaceous and impunctate to finely or coarsely punctate with deep transverse wrinkles, the median line can be clear and deep or only a very shallow furrow.
Elytra: Disc rugose, rows of punctures, shape, and apex typical like in other Plateumaris species.
Legs: Entirely metallic and same colour as upper side. Rarely, some specimens show reddish parts near the joints, mostly on the tibiae or tarsomeres, metafemora of most specimens with a prominent, blade-like tooth, but some specimens with an indistinct or without any tooth.
Pygidium: Emarginate in males, usually rounded but sometimes shallowly emarginate in females.
Aedeagus: Examples of its variability are shown in Fig. 11D, E. There are no reliable external characters to distinguish P. sericea from P. shirahatai. The only reliable feature can be found at the endophallus. The apex of the median ejaculatory guide of the endophallus is notched in P. shirahatai (Fig. 12B) whereas it is rounded (Fig. 12A) in P. sericea. The habitus of P. sericea also looks very similar to P. roscida, but the latter always has large red parts on the legs and antennae, and their aedeagi are strikingly different (Figs 9, 11D, E).
Biology. Plateumaris sericea feeds on Carex sp., Juncus sp., Eriophorum sp., Scirpus sp. and related plant species. For details and identification of the larvae see Steinhausen (1994), Narita (2003) and Bieńkowski and Orlova-Bieńkowskaja 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.   Balthasar (1934) published a small key where he described P. discolor ab. tatrica to distinguish it from P. discolor ab. lacordairii. This is most likely the specimen he examined for this key because it shows exactly the same characters that he mentioned there.
Greece 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 sericea L. and 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 caucasica and sibirica needs further studies. This has been done here for caucasica and 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.
Type material. The holotype is unknown. Remarks. Plateumaris discolor was described by Panzer (1795) as Donacia discolor (Geiser and Geiser 2023), but the morphological variability of P. discolor is within the range of the variability of P. sericea. It was finally synonymised with P. sericea by Askevold (1991) by examination of the endophalli from P. discolor and P. sericea specimens which showed constant characters throughout their distribution area (Fig. 12a), but some authors continue to regard P. discolor as a species propria (Silfverberg 2010;Bieńkowski 2014;Rheinheimer and Hassler 2018); therefore, further arguments are discussed below.
Several characters are used to distinguish P. discolor from P. sericea. The first are the antennomeres: in P. discolor A3 and A4 are a little bit longer than A2, whereas in P. sericea A3 is 1.5× as long as A2 and A4 is twice as long as A2. In fact, the length of the antennomeres is very variable, therefore the difference between "a little bit" and "one and a half" is not clear.
The second is the pronotum disc: in P. discolor it is more punctured and transversely wrinkled whereas in P. sericea it is very finely sculptured. However, the structure of the pronotum disc varies in both "species" in its sculpture and shows an intermediary form in many cases.
The third is the median lobe of the aedeagus, which is also very variable (Fig. 11D, E). This is shown also in the drawings and pictures in identification keys. Sometimes the aedeagus picture of P. discolor in one key looks most similar to the picture of the aedeagus of P. sericea in another key. When a drawing or photograph was made from different angles of view, the same aedeagus can look different in shape and contour. There exist specimens with "discolor" antennomeres and "sericea" pronotum and vice versa. Also, each shape of the aedeagus can occur with any combination of the antennomere or pronotum characters.
Due to these variations, there are no reliable morphological characters to distinguish P. discolor from P. sericea. Other evidence suggests that they may be separate species: P. discolor is reported to be assigned to acid soil and peat bogs where the larvae develop on Carex, Juncus and related plants, whereas P. sericea prefers various wetland habitats with alkaline soil (Rheinheimer and Hassler 2018). Their larvae feeds on Sparganium sp. and Iris pseudacorus (Bienkowsky, 2014). However, P. sericea has such a large distribution area and is very abundant even nowadays in contradiction to almost all other Donaciinae species, therefore, it is more likely that the food plant is also widespread and abundant. This is the case with Carex or Juncus but not with Sparganium and Iris. In the key to Donaciinae larvae in Japan Narita (2003) mentions Carex dispalata Boott. and Scirpus fluviatilis (Torr.) A. Gray as food plants for the larvae of P. sericea. This is definitely not a confusion with P. discolor because the latter does not occur in Japan. Therefore, the assignment to the food plants in Bienkowsky (2014) contradicts the study of Narita (2003) and is in general not a suitable argument that P. discolor is a separate species.
Molecular studies by Hendrich et al. (2015) and J. Bergsten (pers. comm. NHRS, 23 Jan 2023) indicate that P. sericea is genetically very variable. In molecular phylogenetic trees, specimens identified as P. discolor are resolved in between P. sericea specimens, sometimes in groups and separated from P. sericea groups, sometimes not. It is likely that some of these specimens identified as P. sericea are "some kind of" P. discolor and vice versa, because morphological characters are not reliable to distinguish them. There is another problem: it is possible that P. sericea consists of several cryptic species but P. discolor may not be one of them.
Material examined. More than 100 specimens labelled "P. discolor" from different localities in Europe.
Type material. Solsky (1871) did not indicate the depository. It is unknown if the holotype still exists.
Remarks. Plateumaris sibirica was described as Donacia sibirica by Solsky (1871) as a new species from Irkutsk which resembles P. sericea (Geiser and Geiser 2023). It was not described as a "variation" as is sometimes cited in the literature. Jacoby (1885: 193) doubted it: "Donacia sericea var. sibirica? Solsky: The dozen specimens obtained at Nikko show scarcely any difference from our European form … Structural differences I can see none." Eventually, the original description only mentions characters which are typical for P. sericea. It has been regarded as a synonym to P. sericea by Goecke (1960) and Hayashi (2020), but it is treated as a subspecies in Silfverberg (2010), in Warchałowski (2010), and in Bieńkowski (2014). The latter mentioned that "the taxonomic status of the subspecies P. sericea sibirica needs further studies". I examined more than 60 specimens identified as P. sericea sibirica, mainly from the BMNH, NHMB, NMPC and SDEI, and I agree with Jacoby, Goecke and Hayashi that all characters are clearly within the variation range of P. sericea. I could not find any differences compared with European or other Siberian specimens. Therefore, I confirm the decision of Goecke (1960) and Hayashi (2020) that P. sibirica is neither a valid species nor a subspecies, but synonym of P. sericea.
Diagnosis. Pronotal disc rugose, antennae, and legs entirely metallic, although in some specimens the basis of the antennomeres is reddish, A3 = 1.5-2× A2, tooth on metafemur sharp blade-like or obtuse, pygidium of females rounded, in some specimens slightly emarginate, pygidium of males emarginate or truncate, median process of endophallus notched.
Description. Size: Males 6.5-7.3 mm, females 7.8-8.2 mm. Colour: Upper side colour very variable: blackish, blue, green, bronze, cupreous, purple, same colours as P. sericea. Antennae and legs same colour as upper side, in some specimens with reddish parts near the joints.
Head: Rugulosely punctate and pubescent, frontal calli convex, interocular area with a longitudinal median furrow.
Pronotum: Slightly longer than broad, gradually narrowed posteriorly, dorsal surface with a pair of distinctly raised antero-lateral tubercles, and with a triangular depression medio-basally, disc punctate with transverse rugae, median line indistinct, shallowly furrowed.
Elytra: Interstices of the rows of punctures with close oblique or transverse corrugations and showing a rugged appearance.
Legs: Entirely metallic, same colour as dorsum, in some specimens small reddish parts at the base of the joints, tooth of metafemur prominent and blade-like but also in some specimens obtuse.
Pygidium: Apex pubescent, apical shape in females rounded, in some specimens slightly emarginate, in males emarginate or truncate.
Male genitalia: Median lobe of aedeagus (Fig. 13C) very similar to P. sericea (Fig. 11D). Cap of tegmen rounded or slightly notched (Fig. 13B). Apex of median ejaculatory guide of the endophallus notched (Figs 12B, 13F). Remarks. The only reliable feature to distinguish P. shirahatai from P. sericea is the notched apex at the median ejaculatory guide of the endophallus. The habitus of P. shirahatai looks also very similar to P. roscida, but the latter always has large red parts on the legs and antennae, and their aedeagi are remarkably different (Figs 9, 13B, C).
Distribution. East Palaearctic species. The distribution area of P. shirahatai is situated completely within the eastern area of P. sericea. Unfortunately, it is almost impossible to distinguish P. shirahatai from P. sericea without male genitalia. Both species share the same colour spectrum and same variation of the other external characters.
Remarks. At first, I intended to synonymise P. obsoleta with P. sericea based on studies of the type material and description, but doubts remained that it is more likely that P. obsoleta is a synonym with P. shirahatai. I am sure that P. obsoleta, described based on one female specimen and never recorded again in more than 100 years, is a synonym. However, I cannot prove if it belongs to P. sericea or to P. shirahatai because it is impossible to distinguish these two species by external morphological characters. These two species differ only by subtle morphological differences in the apical part of the endophallus (Fig. 12).
Plateumaris obsoleta was described by Jacobson (1894) (see Geiser and Geiser 2023) based on a single specimen collected in Russia, Far East: Posyet in Primorsky Krai. No other specimen of P. obsoleta has been recorded in the last 130 years; it only appears regularly in identification keys. Jacobson found it most similar to P. discolor and P. sericea. All characters he described are also typical characters of P. sericea. Whereas many specimens of P. sericea have a sharp and prominent tooth at the metafemur, in some specimens this tooth can be blunt or is lacking completely. According to Jacobson (1894) this holotype is a male specimen. However, Bieńkowski (2014) wrote in his key: only one single female specimen is known. He also published four drawings of some details of this specimen. In fact, the holotype is stored in ZIN, from which I obtained some detailed photographs (Figs 14, 15, 16).
The controversy about the sex of this specimen can now be solved: the apical part of the ovipositor protrudes, which Jacobson misinterpreted as a part of the aedeagus. Although Askevold (1991) had not seen the holotype, but he suspected that the specimen described by Jacobson was female. According to the original description, "Pygidium apice rotundatum" is a description of a female specimen because no known males of species of Plateumaris have a rounded pygidium. All the characters described by Jacobson and the characters which could be examined on the photographs of the holotype fit easily within the variation range of P. sericea. However, P. shirahatai also occurs in southern Primorsky Kraj (Hayashi and Tominaga 2005). Photographs (Figs 14C, 15A) show that many features of P. obsoleta are consistent with those of Plateumaris shirahatai identified in Primorsky (Fig. 13D, E) including metallic legs and an indistinct median line on the pronotum. In addition, the antennae of P. shirahatai are variable in colouration, with some individuals having the same colouration as the type of P. obsoleta. This strongly supports the possibility that P. shirahatai is a synonym of P. obsoleta. On the other hand, P. obsoleta has a small metafemoral tooth, but it is suspected that the shape of this tooth may be malformed. This is a recurrent problem with species described on single specimen (pers. comm. M. Hayashi, 04 Apr 2023). Therefore, it seems more likely that P. obsoleta is synonym with P. shirahatai than with P. sericea, Figure 15. Plateumaris obsoleta holotype A pronotum B ovipositor protruding from abdomen (photographs by A. Moseyko). that was also suspected by Askevold (1991), Hayashi and Tominaga (2005), and Warchałowski (2010). The pronotum of the type specimen of P. obsoleta (Fig. 15A) looks similar to the pronotum of P. shirahatai (Fig. 13A, D). All in all, the decision of the synonymisation cannot be made now.
Perhaps it will be possible in the near future to solve this problem without destroying this single specimen with more elaborate methods than historical DNA analysis. The solutions used to extract the DNA may be destroy the connecting membranes between the chitinous parts. Nowadays, nobody can guarantee that this specimen would NOT be damaged! Additionally, it is very questionable whether the results will be clear enough. Usually, the DNA in old, stored insects is fragmented and cannot be sufficiently reconstructed to make the decision to which species the specimens belong. Plateumaris sericea and P. shirahatai are closely related, which was proofed by DNA analysis (Hayashi and Sota 2014). There are only few sections of the DNA where the differences are shown. It is unlikely that exact these few sections could be tracked down by the current methods. Therefore, according to the current state of knowledge, I cite it as a "probable new synonymy". If it once can be prooved that P. shirahatai and P. obsoleta are synonyms, the name P. obsoleta has priority because it was described in 1894 and P. shirahatai in 1971. ( The photographs of the syntype of P. weisei and the paratype of P. sachalinensis were examined.

Plateumaris weisei
Taxonomic history and synonymies. This list of synonyms and their shifting positions (see below) indicate the main systematic problems with P. weisei. First, it is difficult to distinguish it from other Plateumaris species. The variety of conspicuous morphological characters (colour, relative length of antennomeres, shape and structure of pronotum, shape of metafemoral tooth, etc.) overlap with other species. Second, the locality name in the first description "Siberie" is anything but precise. Third, P. weisei has a particularly wide distribution range, from northern Fennoscandia through European Russia and Siberia to Far East, Mongolia, Northern China, the Korean peninsula, and Japan. Altogether this resulted in the new descriptions of Plateumaris species when a specimen was found outside Siberia with slightly different characters.
Donacia borealis (Mannerheim), nomen nudum: the first who recognised that a specimen of still undescribed Plateumaris weisei belonged to a new species was Carl Gustav Mannerheim, a Finnish entomologist (1797-1854). He labelled a specimen (possibly more than one specimen, but I only found this one) from In the coll. Frey (NHMB) I found two specimens from Japan, Honshu, Fukushima, labelled "Plateumaris consimilis Schrank det. M. Chȗjȏ", both collected in 1948. These two specimens refer not to P. consimilis orientalis Shavrov but were only misidentifications of P. constricticollis. At this time, the distribution area of P. consimilis was regarded to reach as far as Japan. I never saw a specimen from East of Ural which had some similarity with P. consimilis.
Plateumaris sachalinensis was described by Medvedev (1973) as a new Plateumaris species from the Sakhalin Island (Geiser and Geiser 2023). He compared it with P. weisei in some characters (long antennae, metaformal tooth very weak) but put it close to P. obsoleta (which is synonymous with P. sericea or P. shirahatai). He regarded it as an intermediate form between the P. weisei and P. amurensis group and the P. sericea group. Later, Medvedev (1978) even regarded P. sachalinensis as a synonym of P. obsoleta. I studied the paratype specimen from NMEG: In contrast to many P. weisei specimens which have reddish antennae and legs, in this specimen large parts of the legs are metallic darkened. Probably, this colouration of the legs prompted Medvedev (1973) to place this species close to P. obsoleta. Also, the apical part of each antennomere is darkened. This and the other characters fit easily into the range of variability shown by P. weisei (for more morphological details see . After the study of the original description Askevold (1991: 58) suggested that P. sachalinensis should be regarded as a "probable new synonymy" to P. weisei. Hayashi ( , 2020 and Silfverberg (2010) regarded it as a synonym, Bieńkowski (2014) considered it as a valid species. Warchałowski (2010) separated it in his key from other Plateumaris species because of the dark metallic legs but also mentioned that it is regarded as synonym to P. weisei by some authors. Although Askevold (1991) regarded P. amurensis as synonym to P. weisei, the weak metafemoral tooth of P. sachalinensis is a typical character of P. weisei and excludes P. amurensis here. , who finally separated P. weisei and P. amurensis, confirmed the synonymy of P. sachalinensis with P. weisei.
Diagnosis. Pronotal disc finely rugose and punctured, sometimes with microsculpture, median line obsolete, sometimes shallowly furrowed (similar to P. shirahatai), metafemur with a small, not blade-like tooth, usually rufous at the base; aedeagus with apex of median lobe arced on both sides, gradually narrowed apically, without a median lip.
Head: Eyes small, supraocular furrow indistinct, vertex pubescent with deep median line, antenna entirely rufous in most specimens but in some specimens darkly rufous or apically metallic, antennomeres: A5 longest in second to A6 and ca 3.5× as long as wide, A4 ca 2.2× as long as A2.
Pronotum: Outline subquadrate, slightly longer than wide, basal part narrowed, slightly cone-shaped, anterior tubercles distinctly visible or almost entirely smooth, disc more or less punctate, rugulose, median groove indistinct or shallowly furrowed.
Legs: Yellow-reddish, in some specimens more or less darkened, femur, tibia, and tarsomere pubescent, outer apical angles of pro-and mesotibiae with a spine, outer apical angles of metatibiae with a small spine, metafemoral tooth mostly blunt or moderate.
Aedeagus: Apex of median lobe arced on both sides, gradually narrowed apically, without a median lip, cap of tegmen rounded at apex (Fig. 17).
The main different features between P. amurensis and P. weisei are shown in Table 3. The east Palaearctic Plateumaris species are not easy to distinguish which was also explained in the comments to the synonyms. Misidentifications are common. Oddly enough, in several collections I found the label "Plateumaris [or Donacia] weisei Duvivier" attached to blue specimens from central Asia, collected circa 1900, which in fact were Donacia bactriana Weise, 1887. Somehow the author's name has been shifted and was then regarded as the species name.
Biology. Larvae were found at the roots on Carex sp. (Bieńkowski and Orlova-Bieńkowskaja 2004;. Narita (2003) described the last instar of the larvae which he gained from the host plant Carex middendorfii.
Distribution. Plateumaris weisei is a Trans Palaearctic species, it occurs from northern Fennoscandia through Siberia to the Far East, northern China, the Korean peninsula, and Japan. Also, it occurs in a broad span of latitudes, from the arctic polar circle (67°N)  In Japan records exist only from Hokkaido so far (Hayashi 2020), whereas fossil and subfossil records are known from Honshu and Kyushu, too (Hayashi and Shiyake 2011).
South Korea: Hayashi and Cho (2017); An (2019). Material examined. More than 80 specimens from Europe and Asia.

Discussion
The changes in Geiser (in press) compared with the statuses in Silfverberg (2010) concerned mostly synonymies and country records for Palaearctic Plateumaris species. Forty-one countries or parts of countries could be added to the lists. These records are due mostly to faunistic publications since 2010. Many faunistic studies of small areas have been published in respective local languages and can be easily overlooked. Thanks to colleagues who provided me with such papers, many of these records could now be evaluated. Museum studies and personal communications from colleagues also provided many unpublished records. Thirteen of them were first country records and many others were confirmations of the occurrence of a specific species in these countries.
A primary objective was to declutter doubtful species and ambiguous synonymisations to answer these questions: how many species of Plateumaris exist in the Palaearctic region, what are their names, and how should the remaining 70 names used in a description for a Plateumaris taxon be allocated to the valid species? This was successful in most cases. Additionally, some holotypes could be tracked down, e.g., of P. tenuicornis, which could be identified unambiguously as synonymous with P. consimilis. This also confirmed Bechyné's (1942) opinion that had been ignored. Plateumaris sulcifrons, often allocated to the wrong country, could now be identified as P. rustica by the detailed and clear first description.
In general, this study largely confirmed the systematic status published by Askevold (1991). He stated nine valid species of Palaearctic Plateumaris and I agree with eight of them: his ninth species is P. weisei, which he thought to be synonymous with P. amurensis. Later  concluded that P. amurensis is in fact a valid species, so there are ten species in the genus. I also agree with the opinions of Hayashi and Sota (2014) and Hayashi (2020) about the valid species and their synonyms for Plateumaris.
Many problems could be solved unambiguously, but not all P. obsoleta may be a synonym of P. shirahatai: it could in fact be a synonym of P. sericea, which also occurs at the same locality and cannot be distinguished from P. shirahatai by external characters alone.
A problem does remain concerning the synonymisation of P. discolor with P. sericea. They are not distinguishable morphologically, even if some identification keys suggest that they are. The allocations to their ecological requirements and food plants are contradictory: because P. sericea shows very high genetic variability and has a very large distribution area, it may consist of cryptic species, possibly indicating evolution in progress.
I am reluctant to designate neotypes at this point. Before choosing specimens as neotypes one should be certain that the holotype or type series do not exist. Some museum collections, where I expect to find a missing holotype, could not be visited in the last years due to Covid 19, but this should be rectified in the near future. Additionally, the specimens for neotypes should be from the same location or as near as possible to where the original type or type series were collected, and this require visits to museums in which such specimens are stored.
Finally, I do not want to sweep the most severe problem in researching Palaearctic Plateumaris species under the carpet: the majority of specimens for systematic studies is stored in museums. It is not very hopeful to try to catch specimens in the field. Most museum specimens are by-catches acquired by luck: there exists specimens from expeditions which took place 100 and more years ago from large areas of Asia. From areas like Syria, Afghanistan, and large parts of China such Xinjiang Province, the only information we can access now is from museum specimens. The application of historical DNA methods seems to be helpful but is problematic: its success is questionable, mostly due to the severe fragmentation of the DNA in old specimens. Also, damaging these few very precious specimens by the extraction solution is likely. Perhaps, in the future, there will be gentler methods developed for such studies.
Even without restrictions for field studies caused by politics, in Europe, too, it is difficult to obtain new samples. Many colleagues who know that I am working on Donaciinae have tried to catch specimens during their own field trips in the last years. Besides P. sericea, all other species are rare because of many changes of the limnic environment during the last 100 years. Water pollution is not such an issue as it was 40 years ago, but man-made changes to diverse limnic habitats, especially bank straightening and drainage, has probably led to the extinction of Plateumaris populations that need specific ecological conditions to survive and thrive.
ITMS 26230120004: Building of Research and Development Infrastructure for Investigation of Genetic Biodiversity of Organisms and joining the IBOL initiative.

Author contributions
The author solely contributed to this work.

Data availability
All of the data that support the findings of this study are available in the main text.