﻿Review of the European Eumenes Latreille (Hymenoptera, Vespidae) using morphology and DNA barcodes, with an illustrated key to species

﻿Abstract The European species of the potter wasp genus Eumenes Latreille, 1802 (Vespidae, Eumeninae) are illustrated and a new illustrated key to the 13 recognised species is presented. Eumenesmediterraneusaemilianus Guiglia, 1951 is synonymised with E.papillarius (Christ, 1791) (syn. nov.), E.obscurus André, 1884 and E.andrei Dalla Torre, 1894 with E.pedunculatus (Panzer, 1799) (syn. nov.) and E.crimensis Blüthgen, 1938 with E.sareptanus André, 1884 (syn. nov.).


Introduction
The potter wasp genus Eumenes Latreille, 1802 (Vespidae, Eumeninae) is distributed nearly worldwide and one of the most common genera of Eumeninae foraging on small flowers with easily accessible nectar in southern Europe. The genus currently includes ca. 106 described species (plus 46 subspecies) divided into two subgenera: Kultur GmbH (Linz; BZL), J. Smit collection (Duiven; SCD), Institute of Biodiversity and Ecosystem Research (Sofia; IBER) and National Museum of Natural History (Sofia; NMNHS). Additional specimens were collected in Bulgaria, Greece, Italy, Netherlands, and Turkey by the first author since 1998 and deposited in RMNH. Two COI sequences were used of specimens deposited in the Finnish Museum of Natural History (Helsinki; FMNH). Photographs were taken with a Canon 5Ds 50.6-megapixel camera combined with a Canon MP-E 65 mm f/2.8 1-5× Macro lens, Laowa Macro Twin flash KX-800 and an electronic WeMacro Z-stepper rail. The photographs were stacked with Helicon Focus 7 software. An asterisk indicates a new record for the country. Additional photographs of types were received from Museo Civico di Storia Naturale "G. Doria", Genova, Italy (MSNG; Roberto Poggi), Natural History Museum of Denmark, Copenhagen, Denmark (NHMD; Sree Gayathree Selvantharan), Eidgenössische Technische Hochschule, Zürich, Switzerland (ETHZ; Michael Greeff) and Zoologische Staatssammlung, München, Germany (ZSM; Stephan and Olga Schmidt).
DNA extraction was conducted on single legs, using the NucleoMag 96 Tissue kit by Macherey-Nagel on a Thermo Scientific KingFisher Flex magnetic bead extraction robot, with a final elution volume of 150 µl. The standard COI barcoding fragment (Hebert et al. 2003) was amplified using a cocktail of primers LCO1490 and HCO2198 (Folmer et al. 1994), and LepF1 and LepR1 (Hebert et al. 2004). PCR reactions contained 18.75 µl mQ, 2.5 µl 10× PCR buffer CL, 1.0 µl 10 mM of each primer, 0.5 µl 2.5 mM dNTPs and 0.25 µl 5U Qiagen Taq, with 1.0 µl of template DNA. PCR was performed using an initial denaturation step of 180 s at 94 °C, followed by 40 cycles of 15 s at 94 °C, 30 s at 50 °C and 40 s at 72 °C, and finishing with an extension of 300 s at 72 °C and pause at 12 °C. Bidirectional sequencing was performed at BaseClear (http://www.baseclear.com/). Sequences were edited manually with Sequencher 4.10.1 (Gene Codes Corporation). For all barcoded specimens, sequences and collection data were uploaded to the Barcode of Life Database (BOLD; Figure 1. Showing dark (1a) and pale (1b) type of species 1a Eumenes coronatus (Panzer), female, Finland, habitus lateral 1b E. pomiformis (Fabricius), female, Bulgaria, habitus dorsal. Photographs: C. van Achterberg. Table 1. Sampled specimens from RMNH and J. Smit collection, but both dark specimens of E. coarctatus from Finland are deposited in FMNH. (Linnaeus), female, Netherlands, collecting clay for nest construction 2b abandoned clay nest. Photographs: J.T. Smit. http://www.boldsystems.org/). The voucher specimens are deposited in RMNH and the collection of J. Smit. BOLD accession codes are provided for the specimens that produced DNA barcodes in Table 1.

Molecular data
In the Neighbour-Joining tree (using COI sequences) newly barcoded specimens from Bulgaria, France, Greece, and Netherlands are combined with unpublished older sequences from Finland and Netherlands (Fig. 3). As outgroup we used the related Eumenine Ancistrocerus trifasciatus (Müller, 1776). Table 1 contains details of the barcoded specimens, like country of origin, ID number and BOLD accession number.
First of all, it is clear that E. mediterraneus is a species complex and the characters used for its recognition seems to be insufficient. The lectotype of E. mediterraneus Figure 3. Neighbour-Joining tree for barcoded European Eumenes species. Both E. coarctatus specimens (sampled 5 y ago for another project and not available for examination) among E. coronatus are obviously misidentified and, therefore, in quotation marks. The numbers are RMNH unique identifiers except the Finnish numbers of both dark specimens of E. c. coarctatus from Finland. originates from Croatia (Dalmatia) and is most likely the same species as the sampled specimens from Bulgaria. An extensive survey is necessary to find out what the position of the taxa within this complex is.
The position of the E. coarctatus lunulatus specimen from Bulgaria in the NJ tree indicates that it is different from the sampled N and NW European specimens of E. c. coarctatus (whereas the two colour forms of the latter obviously belong together; Fig. 3). Gusenleitner (1972) treated E. lunulatus as a valid species but later (1999) he lowered its rank to subspecies. In general, as noted by Gusenleitner (1972) Eumenes species become paler and more coarsely sculptured in southern areas than in boreo-montane areas. Likely this is related to thermoregulation of the body; the paler parts reflect sunlight and the heavily sculptured (and thus heavier sclerotised) areas give more protection then the largely smooth and thinner body parts in boreo-alpine species. Eumenes coarctatus lunulatus seems to have a more south-eastern distribution in Europe than the typical E. coarctatus. Eumenes c. lunulatus is more sculptured and paler, indicating a more south-eastern origin than E. c. coarctatus. At the moment it cannot be ruled out that different populations overlap in Central Europe and that we may have to accept that forms with mainly smooth tergites and those with coarse punctures occur in the same taxon as proposed by Neumeyer and Praz (2015) and Neumeyer (2014). Since there is a molecular difference and both taxa or forms seem to exist together in Central Europe, we follow Gusenleitner (1999) and treat E. lunulatus as a valid subspecies of E. coarctatus until more data will become available.
Illustrated key to European species of Eumenes N.B. Species can only be reliably identified by a combination of characters. Setosity may be worn off in aged specimens or hardly visible in dirty specimens; therefore, aged or dirty specimens are easily misidentified. In addition, there is a considerable intraspecific variation.

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Antennal hook short, bent and slightly wider medially (a); apical lamella of second tergite subhyaline or pale yellow (b); second tergite more or less concave medio-posteriorly in lateral view (c); clypeus slightly more emarginated medio-apically (d Eumenes coarctatus corsicus Gusenleitner, 1972Gusenleitner, : 77, 1999 Gusenleitner, 1972Gusenleitner, : 76-77, 1999Gusenleitner, : 569, 2013Castro 1997: 4  Notes. The holotype female of E. coarctatus is heavily damaged (e.g., antenna completely missing) but the metasoma is preserved showing the robust first tergite in lateral view (https://linnean-online.org/16751/) and the second sternite lacks long setae (see van der Vecht 1968, also for the variation of the shape of the first metasomal tergite). The clypeus is entirely black as was likely the anterior face of the scape and, therefore, belongs to the dark typical form.
Distribution. The dark typical form is mostly boreo-alpine of distribution and occurs in Scandinavia (up to S Finland and SE Sweden), UK (England and Wales) and mountainous regions in Central Europe (reaching 1550 m altitude in Switzerland). The pale typical form (= f. barbatulus Blüthgen, 1943) occurs in mainly C and SW Europe and is often the most common species. Outside Europe known from N Africa and the East Palaearctic region up to China and Japan. Only breeding species in UK where it is considered a most threatened species and is known as the Heath Potter Wasp (https://naturebftb.co.uk/artwork/heath-tiger-beetle-alex-hyde/pots-ofthe-heath-potter-wasp-eumenes-coarctatus/).  (Linnaeus), Netherlands (Otterloo), female 4 metasoma lateral 5 first metasomal tergite dorsal 6 first tergite ventral 7 mesosoma dorsal 8 second metasomal tergite latero-dorsal 9 head anterior 10 head and propleuron lateral 11 antenna 12 hind tarsal claw.  Notes. The holotype female of E. lunulatus was digitally examined by using photographs kindly supplied by Sree Gayathree Selvantharan and Lars Vilhelmsen (NHMD). Unfortunately, the head is missing, but the remaining body parts agree with the current interpretation. Gusenleitner (1972) recognised E. lunulatus as a valid species; however, in 1999 he lowered its rank to subspecies because of observed intermediate variation (Gusenleitner 1999). This variation in E. coarctatus sensu lato was one of the reasons to start this revision and thanks to the molecular data (Schmid-Egger and Schmidt 2021; this paper) some provisional conclusions can be drawn. Obviously, Eumenes coarctatus sensu stricto has two forms in Europe: the dark typical one in boreo-alpine Europe and a paler one in C and SW Europe, both with comparatively robust first tergite and antennal hook (Figs 20,21). The SE (and partly C) European specimens belong to E. coarctatus lunulatus as defined in this paper often have a more slender first tergite (but variation is extensive) and a more slender antennal hook in the males (for lateral aspect see Fig. 37). Schmid-Egger and Schmidt (2021) did find differences in CO1 for E. c. coarctatus and E. c. lunulatus, but the latter consisted of a series from Cyprus (probably concerns Blüthgen's ssp. limissicus) and the remainder of E. coarctatus originated from Germany, France, and Italy. We analysed specimens from Finland, Netherlands and Bulgaria and we found the E. c. lunulatus from SE Europe to be different from both the dark (Finland) and pale (Netherlands) forms of E. c. coarctatus (Fig. 3). Neumeyer and Praz (2015) did not find the differences of COI between Swiss specimens of E. coarctatus lunulatus and E. coarctatus sensu stricto substantial enough to recognise E. lunulatus as separate species or subspecies. Earlier Castro and Sanza (2009) came to the same conclusion on basis of Spanish material, but E. coarctatus lunulatus as defined in this paper may not occur on the Iberian Peninsula. An extensive survey is needed to reveal the extent of its distribution and whether or not its status as a valid  subspecies is justified or that it is just a more punctate south-eastern form of E. coarctatus. The yellow dorsal part of the clypeus is more or less reversed U-shaped in f. balcanicus Gusenleitner, 1972. If the clypeus is entirely yellow, middle and hind coxae with a yellow patch and the third sternite largely yellow, see f. ordubadensis Blüthgen, 1938. Distribution. SE and C Europe, NW Asia. Examined specimens originating from Austria (type locality), Hungary, Czech Republic, and Slovakia (but most specimens from these countries in collections belong to E. coarctatus sensu stricto), Italy, Bulgaria, Turkey, Greece (in Peloponnesus the most common species according to Arens (2012, listed Blüthgen, 1943: 297;Gusenleitner 1972Gusenleitner : 86-87, 1999Gusenleitner : 570, 2013 Blüthgen, 1956: 2;Gusenleitner 1972Gusenleitner : 85, 1999van der Vecht and Fischer 1972: 127;Castro 1997: 4 (as synonym of E. coronatus); Gereys 2016: 128 (id.); Fateryga 2017: 181 (id.). Eumenes coronatus corruetus Gusenleitner, 1972Gusenleitner, : 87, 1999Gusenleitner, : 570-571, 2013 Notes. Males from the Balkan Peninsula have the apical half of antennal hook distinctly flattened, different from the wider apical half in Central European males (Fig. 54).

Eumenes coarctatus lunulatus
Distribution. Rather common in most of Europe (including southern Scandinavia; Abenius 2012), but absent in the UK. In Switzerland up to 1640 m altitude, but in Peloponnesus (S Greece) not found above 1200 m altitude (Arens 2012). Outside Europe in Israel, Turkey, Iran and in East Palaearctic region up to Mongolia, China, and Korea.

Eumenes cyrenaicus Blüthgen, 1938 Figs 55-74
Eumenes dubius cyrenaicus Blüthgen, 1938: 464, 468 (Fig. 65); Sardinia, Spain and Portugal, N Africa) to blackish brown (Italy, N Macedonia, Greece, Bulgaria, Turkey, but sometimes also pale brown (Fig. 55); Gusenleitner (1972) already mentioned the variability of this character for E. dubius in Asia. The separation of E. cyrenaicus from E. sareptanus is mostly based on colour differences and, therefore, may be problematic. In general, females of E. cyrenaicus have a more robust first tergite, including the petiolate part and males have the antennal hook more curved than in E. sareptanus.

Eumenes dubius
Notes. This species is in need of a critical revision; the few molecular data indicate that several cryptic species may be included under E. mediterraneus (Fig. 3). The lectotype male of E. mediterraneus originates from Croatia (Dalmatia) and was examined digitally by photographs kindly supplied by Stephan and Olga Schmidt (ZSM). It has the apical hook of the antenna less curved than pictured in Fig. 111 and its basal half densely setose. The sampled specimens from Crete and Corsica are different (Fig. 3) and a large-scale revision with sufficient fresh material from all over Europe is needed to sort out the relationships within the E. mediterraneus complex.
For the populations of Corsica and Sardinia the name of E. m. filitosa Gereys is available; supposed to differ in most cases by the entirely black fifth tergite or largely so because of one or more small yellow patch(es) (in E. mediterraneus usually with complete yellow apical band, but absent in figured typical E. mediterraneus (Fig.  94)). Possibly the strongly convex second metasomal tergite and deeper subposterior depression may be of importance for its separation. For the population of Cyprus ssp. cypricus Blüthgen is available and differs by having the punctures of vertex, mesoscutum and second metasomal tergite at least twice larger than in typical E. mediterraneus (Gusenleitner 1972). Distribution. Mediterranean, Balkan Peninsula, rarely in Central Europe (e.g., Switzerland only in Ticino and Valais and late in season (July-October; Neumeyer 2019) and very rarely collected in Germany (Frommer 2012;Reder 2022). In Greece starting in April and present in lowland and submontane habitats (Arens 2012). Reported from Asia up to Turkey, Iran, Afghanistan, Saudi-Arabia, China, Korea, and India, but this probably will change after a full revision (including molecular research) considering the uncertainty about the number of taxa under E. mediterraneus in Europe.

Eumenes papillarius (Christ, 1791) Figs 112-131, 262-266
Sphex papillarius Christ, 1791: 325. Eumenes papillarius; Tobias and Kurzenko 1978: 160;Hensen 1985: 45;Castro 1997: 4;Schmid-Egger and Schmidt 2002: 18;Schmid-Egger 2004: 72, 2010Smit et al. 2004: 327;Woydak 2006: 41-44;Castro and Sanza 2009 Notes. Large specimens (fore wing length about 10 mm) have frequently a pair of yellow patches on the mesoscutum antero-laterally; the patches vary from minute to large. The photographs of the female holotype kindly supplied by Roberto Poggi (MSNG) show that E. aemilianus Guiglia, 1951 is a junior synonym of E. papillarius (Christ, 1791) (syn. nov.) because of the entirely dark brown labrum (Fig. 265), the shallow apical emargination of the clypeus (Fig. 265), the pair of large yellow patches on the mesoscutum (Fig. 264) and the medium-sized setosity of the second tergite (mentioned in the original description). The holotype female (deposited in MSNG) is a comparatively yellowish specimen with slender first tergite, it has the clypeus narrowly black apically, the mesoscutum with a pair of large and curved yellow lateral patches, the apex of the antenna black and the apical rim of the second tergite pale yellowish (Figs 262-266). The presence or absence of a pair of yellow mesoscutal patches is a variable (and at least partly size related) character in E. papillarius and does not indicate that it concerns a separate species (see also comments of Gusenleitner (1972) under E. papillarius). Aberrant specimens from the Iberian Peninsula have medium-sized to long setae on the second sternite and the apex of the hind tibia is yellow. The apical lamella of the second tergite varies from pale yellowish to dark brown.
Distribution. Widespread in most of Europe, but considered absent from UK (only known as vagrant in England; Archer 2014), Norway, Sweden and Finland. Found up to 1550 m altitude in Switzerland (Neumeyer 2019), but in S Greece rather rare and restricted to lowland and submontane habitats (Arens 2012). This species is often found near human settlements and using small crevices of buildings (e.g., under roof tiles) to construct small groups of clay nests.

Eumenes pedunculatus (Panzer, 1799) Figs 132-149
Vespa pedunculata Panzer, 1799: (6) Blüthgen, 1943: 302;Gusenleitner 1972Gusenleitner : 82, 1999 Notes. The depository of the female holotype of E. obscurus André (= E. andrei Dalla Torre) is unknown, but the extensive description allows identification. The robust posterior part of the first tergite (in dorsal view campaniform), the entirely dark antenna, the black clypeus except for a yellow dorsal linear patch and the shiny and very finely punctate second tergite points to E. pedunculatus (Panzer). The type series of E. marginellus is lost; the more or less yellow scape, the black scutellum, the narrow yellow patch of the pronotum and narrow yellow posterior patch of the first tergite are similar to some examined specimens of E. pedunculatus. Distribution. Widely distributed in Europe but relatively rare in collections from NW and S Europe (e.g., only Eumenes sp. known from Norway, absent from UK and Corsica, in S Europe rare and restricted to montane habitats (Arens 2012;Gereys 2016)). Outside Europe known from the East Palaearctic region up to Japan and Korea. Associated with Calluna-Pinus heaths (Woydak 2006) and occurring up to 1850 m altitude in Switzerland (Neumeyer 2019) and 2550 m in Spain (Gereys 2016).

Eumenes sardous
Distribution. An endemic species of Sardinia (Italy) and Corsica (France), occurring from sea level up to 1600 m altitude in Corsica (Gereys 2016 Notes. Castro (1992) concluded that traditional characters do not suffice to separate E. sareptanus from E. dubius after studying a large series of Spanish specimens. The observed variation is considered to be clinal and connected to climatic conditions (indicated by latitude and altitude). Therefore, both Castro (1992) and Gereys (2016) consider all European specimens of E. sareptanus and E. dubius conspecific, with the latter as oldest and thus valid name. It is obvious that with the differences used in existing keys both species are not well separable, this is especially the case for the females. The apical antennal hook of E. sareptanus is generally more slender than in E. dubius (Figs 224,226 versus Figs 89,92), albeit that the difference is less obvious in part of the SW European males. Traditionally, E. sareptanus is separated from E. dubius by having the setae of the mesoscutum about as long as apical width of scape and the apical lamella of the second tergite longer than height of the preapical vertical depression of the tergite. In this paper we propose a different combination of characters, but it is obvious (also from the molecular data presented in Schmid-Egger and Schmidt (2021)) that both are valid species. More research is needed to clear up the interrelations in the group of E. dubius (viz., E. dubius, sareptanus, cyrenaicus).   Blüthgen (1938) described Eumenes dubius crimensis from Crimea (Jalta; only ♀-holotype and a ♂-paratype) mainly based on the coarser punctation of the mesoscutum ("Punktierung des Thorax grob, überwiegend met deutlichen, glatten, glänzenden Punktzwischenräumen, ….") and length of its setae (intermediate between typical E. sareptanus (long setae) and typical E. dubius (short setae)). Gusenleitner (1972) examined a series from Crimea that contains only typical E. dubius specimens. In addition, he has seen specimens from Kopet Dag (= the border area of Turkmenistan and Iran) that fit better with the original description than specimens from Crimea. Fateryga (2018) agrees that these are different from the Crimean specimens and the specimens reported as E. crimensis from Iran, C Asia and Kazakhstan likely belong to E. scabrosus with slender aedeagi (Fateryga 2018). Gusenleitner (2013) treated E. dubius crimensis as a valid species without any comment, but the status of E. crimensis was discussed by Fateryga (2018). Considering the shape of the depicted aedeagi by Fateryga (2018) it could be E. dubius as well E. sareptanus; both have the medial part of the aedeagi similarly shaped.
Unfortunately, the original description does not include any remarks on the shape of the apical antennal segment of the male. The males should have the apical antennal segment narrower basally and less curved than in typical E. dubius according to Gusenleitner (1972). Michael Greeff (ETHZ) kindly supplied the first author with photographs of the male paratype, which clearly shows that it is not E. dubius because of the comparatively slender apical antennal segment which fits well with the apical segment of E. sareptanus. The latter species has coarser punctures (often with distinct smooth interspaces) on head and mesosoma dorsally than in E. dubius, yellow area of pronotum more widened compared to median width, and first metasomal tergite latero-apically broadly yellow. All these characters are present in the paratype of E. crimensis and, therefore, we synonymise E. crimensis with E. sareptanus (syn. nov.). Distribution. A comparatively rarely collected species in C and S Europe as well in NW Asia. The typical form occurs in southern European Russia up to western Siberia. In Switzerland occurring between 255 and 1250 m altitude (Neumeyer 2019). Blüthgen, 1938 Figs 227-243 Eumenes subpomiformis Blüthgen, 1938: 480, 496;Gusenleitner 1972Gusenleitner : 101-103, 1999Gusenleitner : 574, 2013Tobias and Kurzenko 1978: 161;Castro 1997 Notes. As pointed out by Gusenleitner (1972) E. subpomiformis is very similar to E. pomiformis ("Eumenes pomiformis steht der Art subpomiformis sehr nahe und nicht der Art lunulatus") and is easily misidentified when the medium-sized or long setae of the propleuron of E. subpomiformis are not well exposed (head too much down), depressed or damaged. He also correctly denounced the differences in shape of the clypeus as illustrated by Blüthgen (1938) ("Die Form des Clypeus, wie sie Blüthgen für subpomiformis angibt (Ausschnittecken nach den Seiten gezogen) tritt auch bei pomiformis auf ".) What remains in both sexes for separation according to the keys by Gusenleitner (1972Gusenleitner ( , 1999 is the length of the setae on the propleuron (with equal shorter setae in E. pomiformis and with unequal longer setae in E. subpomiformis). However, the setosity seems rather variable (especially in males) and should be used in combination with other characters. Recent molecular research (Neumeyer and Praz 2015; Schmid-Egger and Schmidt 2021; this paper) revealed distinct genetic differences between E. subpomiformis and E. pomiformis (Fig. 3) despite their overall similarity. Specimens in RMNH identified by Blüthgen (in 1950 and1955) as E. pomiformis barbatulus belong either to E. subpomiformis (Portugal; females with mostly comparatively short setae on propleuron and deeply emarginate clypeus) or to E. coarctatus (most specimens (with medium-sized to long setae on propleuron) from Portugal, Spain, France, Algeria, Morocco).