New records of German Scelionidae (Hymenoptera: Platygastroidea) from the collection of the State Museum of Natural History Stuttgart

Abstract Background Scelionid wasps are arthropod egg parasitoids, many of which are relevant to global biosecurity. However, the scelionid fauna of Germany has not received much attention from professional taxonomists. New information Eleven species and four genera are recorded for the first time from Germany, including species of interest to agriculture and biological control. First genus records include Baryconus Förster, Macroteleia Westwood, Paratelenomus Dodd and Probaryconus Kieffer. First species records include B.europaeus (Kieffer), Idrisnigroclavatus (Kieffer), Idrissemiflavus (Kieffer), M.bicolora Kieffer, M.pannonica Szabo, Paratelenomussaccharalis (Dodd), Trimorusvaricornis (Walker), Trissolcusbasalis (Wollaston), Trissolcusbelenus (Walker), Trissolcuscolemani (Crawford) and Trissolcusflavipes (Thompson). COI barcodes are identified for the first time from B.europaeus and M.bicolora. Each species is illustrated and updated world distributions are provided. Implications for agriculture are discussed.


Introduction
Platygastroidea is the third largest superfamily of Hymenoptera in terms of the number of described species, exceeded only by Ichneumonoidea and Chalcidoidea. The current number of valid species is ca. 6,500, with a worldwide estimate of about 10,000 (Hymenoptera Online 2020, Masner 1993, Johnson 2011. At the time of writing, the superfamily comprises two extant families, Scelionidae and Platygastridae Buffington 2015, Popovici et al. 2017).
In the 19th century, several notable experts published on German Platygastroidea. The earliest was Christian Gottfried Nees von Esenbeck, who described dozens of species in Sparasion, Scelio, Platygaster and Teleas ( Nees von Esenbeck 1834). Julius Theodor Christian Ratzeburg described species of Platygaster and Teleas associated with forest pests (Ratzeburg 1852). Soon after, Arnold Förster published his "Hymenopterologische Studien", establishing 26 platygastroid genera, many of which remain valid today (Förster 1856). In the early 20th century, Jean-Jacques Kieffer described numerous genera and species from central Europe, including German material (Kieffer 1926).
Since Kieffer, there has not been much research on the Platygastroidea of Germany. The most recent catalogue of German insects (Dathe et al. 2001) lists 136 platygastroid species, including 56 Scelionidae. However, these numbers are certainly low. The section was based on a relatively short reference list and many common European taxa were not included. Thus, Platygastroidea has been identified as a priority for research within the German Barcode of Life III: Dark Taxa project (Hausmann et al. 2020). Dark taxa are insect groups, mainly in Hymenoptera and Diptera, which pose a taxonomic impediment to biodiversity studies. Such taxa are abundant and diverse in insect monitoring projects, but a lack of usable diagnostic literature makes species identification difficult to impossible.
Scelionid wasps parasitise the eggs of arthropods, including many invasive or noxious pest species (Austin et al. 2005). Thus, their accurate identification is critical to agricultural research, especially in the context of the global plant trade. For example, the brown marmorated stink bug, Halyomorpha halys Stål, 1855, is an invasive species in Europe and North America. Its most effective natural enemy, Trissolcus japonicus (Ashmead, 1904), has been detected or established as an adventive species throughout the introduced range (Talamas et al. 2015, Abram et al. 2019, Stahl et al. 2019. Most recently, T. japonicus was detected in Germany (Dieckhoff et al. 2021). Similarly, Paratelenomus saccharalis (Dodd, 1914) has followed the kudzu bug, Megacopta cribraria (Fabricius, 1798), from the Palearctic into North America (Gardner et al. 2013).
The current work represents a first update to the German platygastroid fauna within the German Barcode of Life (GBOL) III initiative. As these findings occurred within the first several months of the project, further discoveries are expected over the next three years. Identification of Platygastridae is still underway, as the state of taxonomic disarray in this group is more severe.

Materials and methods
We examined recent and historical collections of Scelionidae at the State Museum of Natural History Stuttgart (SMNS). Recent material was collected for earlier stages of the GBOL project or for long-term insect monitoring programmes, generally by Malaise trap. Recently-collected specimens were preserved in 96% ethanol. Specimens collected for the GBOL project had DNA extracted non-destructively with the DNeasy Blood & Tissue Extraction Kit from Qiagen following the updated protocol provided by Cruaud et al. (2019). COI barcodes were amplified by PCR with the LCO1490/HCO2198 primers (Folmer et al. 1994). Barcode sequences are available at GenBank accession numbers MW829349-MW829358.
Illustrations were created with a Keyence imaging system. Adobe Photoshop was used for image processing and plate construction.

Distribution
Baryconus europaeus ( Fig. 1) was described from Italy and has also been recorded from Croatia, Cyprus, France, India, Japan, Morocco, Portugal, Russia, Spain, Turkey and UAE (Popovici et al. 2013). It is expected in Romania (Spiridon et al. 2019). We here provide the first genus and species record for Germany and the first identified barcode for Baryconus europaeus. Identification is based on Popovici et al. (2013).

Distribution
Idris semiflavus (Fig. 3) was described from France and has been recorded from Egypt, Hungary, Italy, Mongolia, Spain and Switzerland (Huggert 1979). We here provide the first species record for Germany. Identification is based on Huggert (1979).

Distribution
Macroteleia bicolora (Fig. 4) was described from Italy and has also been recorded from Denmark, Kazakhstan, Russia, Ukraine and the United Kingdom (Kozlov 1987, Notton et al. 2014. We here provide the first genus and species record for Germany and the first identified barcode for Macroteleia bicolora. Identification is based on Kozlov (1987).

Distribution
Macroteleia pannonica (Fig. 5) was described from Hungary and has also been recorded from Romania (Fabritius andPopovici 2007, Kononova andKozlov 2008). We here provide the first genus and species record for Germany. Identification is based on Kononova and Kozlov (2008).

Distribution
Trimorus varicornis (Fig. 8) was described from Ireland and has also been recorded from Bulgaria, Croatia, Denmark, Finland, France, Italy, Romania, Russia, Sweden, Switzerland, Ukraine and the United Kingdom (Fabritius and Popovici 2007, Hymenoptera Online 2020, Kononova and Kozlov 2001). We here provide the first species record for Germany. Identification is based on Kozlov (1987).

Distribution
Trissolcus belenus (Fig. 10) was described from the UK and has also been recorded from China, France, Iran, Italy, Morocco, Portugal, Russia, Sweden, Switzerland and Tanzania

Distribution
Trissolcus colemani (Fig. 11) was described from India and has also been recorded from China, France, Greece, India, Iran, Italy, Morocco, Pakistan, Russia, Sweden, Ukraine and the United Kindgom . We here provide the first species record for Germany. Identification is based on .

Distribution
Trissolcus flavipes (Fig. 12) was described from Sweden and has also been recorded from Austria, Denmark, France, Hungary, Japan, Moldova, Romania, Russia, Sweden, Thailand, Ukraine and the United Kingdom (Talamas et al. 2017). We here provide the first species record for Germany. Identification is based on Talamas et al. (2017).

Discussion
Of the two families of Platygastroidea, Scelionidae is better resolved. High-quality revisions and keys are available for many genera of Scelionidae, due to careful attention from professional taxonomists, as well as data regarding ecological and biological aspects. Platygastridae has been somewhat more neglected and, in large genera, such as Platygaster Latreille and Synopeas Förster, better diagnostic tools are needed for accurate species identification. This is the case with some genera of Scelionidae as well, such as Gryon Haliday and Telenomus Haliday. For example, one-hundred-year-old specimens of Telenomus still remain unidentified in the collection of SMNS. As taxonomic issues are resolved, it will become possible to accurately identify material for barcode reference libraries.
Baryconus europaeus and Macroteleia bicolora are here barcoded for the first time. A comparison with existing records in BOLD Systems (https://www.boldsystems.org/) showed no matches to identified material. For the M. bicolora sequences, the highest match (93.62%) was to unidentified specimens from Gabon. The B. europaeus sequence was most similar (97.63%) to unidentified specimens from South Africa. As expected, all Trissolcus sequences matched well (at least 99%) with appropriately identified material.
Based on preliminary data, several species of Probaryconus are found in Germany, but their nomenclature is uncertain, due to the aforementioned taxonomic impediment. Historical Trissolcus specimens remained unidentified in the SMNS collection for 50 to almost 100 years. The oldest of these, T. colemani, was reared from hemipteran eggs in 1932 (Fig. 11). A series of T. belenus from 1971 are preserved along with host material (Fig. 10). It is no surprise that these specimens were never identified, since T. belenus was largely overlooked for nearly two centuries before it was properly examined and keyed by .
In addition to the newly-recorded species, Trissolcus species already known from Germany, such as T. cultratus (Mayr), T. semistriatus (Nees von Esenbeck) and T. scutellaris (Thomson), have been repeatedly detected at various locations in Baden-Württemberg. The last checklist of German Scelionidae (Dathe et al. 2001) also includes T. choaspes (Nixon), T. discolor (Ratzeburg) and T. rufiventris (Mayr). Trissolcus choaspes is now a junior synonym of T. scutellaris (Thomson) (Talamas et al. 2017). The taxonomic status of Trissolcus discolor is unverifiable, as there is no known type material and some authors even debate whether T. discolor should be placed in Telenomus rather than Trissolcus (Kononova 2014). As for T. rufiventris, it was not found, which we think is an intriguing matter considering the number of Trissolcus specimens examined by C.V. at SMNS.
Our results emphasise that much remains to be discovered regarding parasitoid ecosystem services in Germany. Many of the newly-recorded species parasitise the eggs of stink bugs which pose a threat to vegetable and fruit production. As wasp species differ in their host preference and biological control efficacy, accurate identification is an important factor in agroecological studies (Scaccini et al. 2020). The effect of the scelionid species assemblage on local pest populations merits further attention, especially in the context of organic or sustainable food systems.