The main source of material includes specimens from the collections of the Zoologische Staatssammlung München (ZSM) and from the private collection of Christian Schmid-Egger (CSE). If no suitable specimens of German species were available from German territory, specimens collected from neighbouring countries were used, in particular from northern Italy and from the Czech Republic.

For the identification of Vespidae, Neumeyer (2019) was used, for other families Amiet (2008). Mutillidae and Myrmosidae from Central Europe were covered by Lelej and Schmid-Egger (2005), and Thynnidae from Europe and the Palaearctic region by Boni Bartalucci (2004, 2012). A checklist and a red list of German aculeate wasps with all species reported from Germany was provided by Schmid-Egger (2011). Scoliidae were identified using Osten (2000), Sapygidae using Kurzenko and Gusenleitner (1994), and Agnoli (2005) for Methochinae.

For DNA extraction, a single leg was removed from each specimen and sent to the Canadian Centre for DNA Barcoding (CCDB) in Guelph, Canada for DNA extraction and barcode sequencing. A complete list of voucher specimens included in the current release is given in Suppl. material 1.

DNA extraction, PCR amplification, and sequencing were conducted at the Canadian Centre for DNA Barcoding (CCDB) using their standardised high-throughput protocols (Ivanova et al. 2006). The 658 bp target region, starting from the 5’ end of the mitochondrial cytochrome c oxidase I (COI) gene, includes the DNA barcode region of the animal kingdom (Hebert et al. 2003). Specimens that were successfully sequenced are listed in Suppl. material 1, with country of origin, collection date, sequence lengths and the number of unresolved bases. DNA barcoding statistics with mean and maximum intraspecific distances, distance to nearest species, BIN, country of origin and number of barcoded species are listed in Suppl. material 2. All specimen data are accessible in BOLD as a single citable dataset (https://doi.org/10.5883/DS-GBVEOCE). The data include collecting locality, geographic coordinates, elevation, collector, one or more digital images, identifier, and voucher depository. Sequence data can be obtained through BOLD and include a detailed LIMS report, primer information, and access to trace files.

Sequence divergence statistics were calculated using the Kimura two parameter model of sequence evolution (Kimura 1980). Sequences were assigned a Barcode Index Number (BIN) by the BOLD system. BINs represent globally unique identifiers for clusters of sequences that correspond closely to biological species (Ratnasingham and Hebert 2013). For aculeate wasps, BINs largely support the taxonomy based on traditional approaches using morphology (Schmidt et al. 2015; Schmid-Egger et al. 2018). For BIN assignment, a minimum sequence length of 500 bp is required, and sequences between 300 and 500 bp can join an existing BIN but will not create new or split existing BINs.

BINs provide an interim taxonomic system that allows defining species as Molecular Taxonomic Units (MOTUs) prior to detailed taxonomic studies including morphology. Sequences were aligned using the BOLD Aligner (amino acid-based hidden Markov models). The analyses are based on sequences with a minimum length of 500 bp and < 1% ambiguous bases. Genetic distances and summary statistics were calculated using analytical tools in BOLD and are given as mean and maximum pairwise distances for intraspecific variation, and as minimum pairwise distances for interspecific variations.

All species treated here key out as S. rufipes in the keys of Lelej and Schmid-Egger (2005) and Amiet (2008).

Males

Females

The present study presents DNA barcodes for 134 species of Vespoidea, including 103 (90%) of the 114 species that were recorded from Germany. The release represents, after the bees (Schmidt et al. 2015) and the apoid wasps (Schmid-Egger et al. 2018), the third major DNA barcoding release of German aculeate wasps. Each contribution covered a similar percentage of the German species, with the difference that the species numbers of bees and apoid wasps are, with 584 and 273 species, respectively, considerably larger than the Vespoidea. All three barcode releases together allow the reliable identification of 843 German species of bees and wasps, comprising of about 82% of the German fauna of aculeate wasps and bees. Therefore, virtually any bee or wasp that is collected on German territory can by now be identified using DNA barcoding (barcode releases of the remaining families Pompilidae and Chrysididae, with similar percentages of barcoded species, are currently in preparation). Species that are still missing in our dataset are either extremely rare or even extinct in Germany. Obtaining barcoding sequences of these species will depend on the availability of specimens from countries other than Germany or barcoding of, often historic, specimens from museum collections.

None of the barcoded vespoid species exhibited BIN sharing, and barcodes allow their unambiguous identification. BIN divergence was detected in 15 species (11%), suggesting either large intraspecific variation or presence of undetected species that were not recognised by taxonomists before. In species with BIN diversity, new taxa were formally described if genetic diversity was associated with diagnostic morphological differences. Undoubtedly, DNA barcoding expedited the discovery of the new taxa that would have been very unlikely by a traditional, morphology-based approach.

Several species of Vespoidea show a distribution pattern that appears to be a result of the separation of populations during periods of glaciation, when the species retracted from Central Europe to regions not covered by ice, and their re-invasion during warmer periods (Hewitt 1999; Schmidt 2018). If populations came into contact again during post-glacial warming, differences that accumulated during isolation might prevent them from intermixing, albeit morphologically still very similar (de Lattin 1967). The Upper Rhine Valley in south-western Germany is known as an area with populations of xerothermic species that origin from the Mediterranean area and represent a northern outpost (Westrich 2018; Schmid-Egger 2020; Schmitt 2020). DNA barcoding revealed that several species of Vespoidea seem to reflect this distribution pattern, with one species that is widespread and often common in Central Europe north of the Alpes, and another, morphologically similar species that is restricted in its distribution to the Upper Rhine Valley and sometimes other parts of south-western Germany. Examples include several taxonomically problematic species of the genera Tiphia, Myrmosa, and Smicromyrme. In addition, a third species of each species complex often occurs in northern Italy, northwards into the southern Alps, with its western limits demarcated by the south-western Alpine arc along the border between Italy and France, as in the case of Smicromyrme langobardensis sp. nov. This distribution pattern has long been known in Hymenoptera (de Lattin 1967), including bees and apoid wasps (Schmidt et al. 2015; Schmid-Egger et al. 2018), and can, in some cases, aid in refining species limits in taxonomically problematic taxa. It originates most probably from three retreat areas during ice age, including the Iberian Peninsula, Italy, and the Balkans (Schmitt 2020).

Vespoidea are generally known for their, compared to most other Hymenoptera, large body size and by their low species diversity, and have therefore for a long time attracted the attention of hymenopterists. Of the 114 species recorded from Germany, more than 90% were described during the 18^th and 19^th centuries. The taxonomy of most of them has not changed since then and most species are accepted as valid to the present day, except species of taxonomically difficult genera like Eumenes Latreille, 1802 (Vespidae, Eumeninae). The BIN divergence of species in several families of the Vespoidea came therefore as a surprise and even led to the discovery and description of new species. BIN divergence was even higher in some species of Polistes (Vespidae, Polistinae) that were treated in detail in an earlier study (Schmid-Egger et al. 2017). After more than 100 years of mostly taxonomic stasis in the Vespoidea, DNA barcoding provided the incentive for scrutinising the taxonomy of several species in this group. It laid the foundation for subsequent analyses using integrative approaches combining DNA sequences and morphology, and analysis of supplementary characters systems that allow to refine the species boundaries, for example cuticular hydrocarbon profiles (Soon et al. 2021).

In absence of morphological differences between representatives of different BINs within a traditional species, we refrained from establishing new species, an approach that has also been followed during previous DNA barcoding studies, even when high levels of genetic diversity were detected within a traditional species (Schmid-Egger et al. 2017; Hansson and Schmidt 2018). In such cases, a thorough taxonomic study led to the discovery of morphological differences that were not detected by taxonomists before, but probably would have been discovered when the species question would have been scrutinised by specialists. However, in absence of any new taxonomic insights that would have triggered a taxonomic re-evaluation, species would have most probably been overlooked. DNA barcoding provided these cues and, for example, led to the description of a new species of velvet ants from Germany after more than 130 years. Other examples with DNA barcoding triggering taxonomic discovery included discovery of sibling species in the genus Tachysphex from Central Europe (Straka 2016) and the Alpine bee Andrena amieti Praz, Müller & Genoud, 2019. The species was discovered during previous DNA barcoding efforts on German bees (Schmidt et al. 2015) but was only recently described as part of a comprehensive species level revision (Praz et al. 2019).

Species with BIN divergence but without any morphological characters to support the species status of BIN representatives remain problematic. These include species like Myrmosa atra and Tiphia femorata, with two and five BINs, respectively, and maximum intraspecific distances of 8.9% in M. atra and 13.1% in T. femorata. If these genetic distances signify species diversity, then they are not correlated with equally pronounced morphological differences. Morphological examination did not reveal any consistent differences that would allow their separation, and we therefore left the species status of both species as is until further evidence will allow to decide this way or the other. This situation may seem unsatisfactorily at first sight, but it demonstrates a major difference between conventional and barcode-aided taxonomy. Traditionally, one was left with a species name, resulting either from the identification of a specimen using a key, or a name provided by a specialist, usually based on the most recent taxonomic revised of the taxon in question. However, a species name alone does not convey any information about intraspecific variation, nor distances to related species, information that would be critical for assessing the identity of a particular specimen. A name in combination with a DNA barcode, on the other hand, allows sequences and genetic distance information that accurately characterise a specimen to be carried over to subsequent taxonomic treatments aiding in resolving the taxonomic status, in particular if this information is publicly accessible. This would avoid losing information like distribution and life history traits, as it can happen when erroneously lumping species (Sharkey et al. 2021). The name, in combination with the DNA sequence and the Barcode Index Number, allows a much more accurate characterisation of species than morphology alone. Furthermore, and unlike morphological data, from sequences distance measures can be calculated between specimens, populations and species and continuously re-assessed as more barcodes are added to the reference database. Once the barcode structure of a species is has been assessed, it can be accurately and reliably identified and referred to in scientific research.

For species with an intraspecific variation larger than the commonly applied genetic distance threshold of 2%, and with multiple BINs, the information should be available “as is” in the globally accessible Barcode Life Database, including sequence data, photographs, collecting data and other supplementary information. Subsequent taxonomic assessment of these taxa based on morphology alone will most likely not aid much in refining species boundaries, and we therefore propose to use the current name in combination with an identifier like the Barcode Index Number (BIN) and a link to the auxiliary information in BOLD until sufficient data is available to clarify complexes of taxonomically problematic species.