Checklist of the Ichneumonidae of Germany (Insecta, Hymenoptera)

Abstract Background A revised checklist of the Ichneumonidae of Germany is provided. The list represents an updated version of an earlier checklist published in 2001. The present list includes several records of species that are new for the German fauna and species that were discovered since the last checklist was published. The present checklist was compiled as part of the DNA barcoding projects at the Zoologische Staatssammlung München. New information The checklist includes 3,644 species of Ichneumonidae from Germany, with 48 species recorded for the first time. Compared to the checklist published 20 years ago, the number of ichneumonid species recorded from Germany has increased by 312 species.


Introduction
The Ichneumonidae is the largest family of insects in Germany, with over 3,600 species already recorded for the country and an estimated number of 4,000 species in total (Horstmann 2002a). The family Ichneumonidae and its sister family Braconidae, with about 1,500 German species (Belokobylskij et al. 2003), account for about half of the German species of the insect order Hymenoptera (Völkl and Blick 2004).
The first comprehensive and validated checklist of ichneumonid species that were recorded from Germany was provided by Horstmann (2001a). When compiling the checklist, he included only species that were either described as new after 1945 or, if the species was described before 1945 or if it was mentioned at least once in the entomological literature after WWII. Horstmann (2001a) excluded species that were mentioned only once in the literature prior to 1945, i.e. in the original citation, because, according to him, virtually all of those species represent synonyms. If the species were cited after 1945, he included it only if it was accompanied by a taxonomic treatment. Following this rationale, it was possible for him to compile a checklist that comprises only reliable records while reducing the risk of including species with doubtful status.
The list was compiled as part of DNA barcoding projects at the Zoologische Staatssammlung München (ZSM) that aims at assembling DNA barcode libraries for Germany (German Barcode of Life Project, www.bolgermany.de) and Bavaria (Barcoding Fauna Bavarica). A new checklist was deemed necessary because of the relatively large number of species that were added since the last checklist was published 20 years ago by Klaus Horstmann (2001a) and because of several nomenclatorial changes (e.g. synonymy) and recent modifications to the classification within the family (Broad and Shaw 2005, Bennett et al. 2019, Klopfstein et al. 2019, Santos 2017. Most records of species new to Germany, a few of which are depicted in Fig. 1, resulted from extensive collecting efforts as part of past and ongoing projects on DNA barcoding (Hausmann et al. 2020, Morinière et al. 2016).

Materials and methods
The present checklist is an updated version of the checklist of German Ichneumonidae provided by Horstmann (2001a). Most additions to the new checklist are based on records that were published since the previous checklist (Horstmann 2001a). Identifications of species that are recorded as new for the German fauna were identified by specialists as part of the ongoing DNA barcoding efforts at the ZSM. Representatives of newly-recorded species are deposited in the ZSM or in the author's private collections.
The classification follows Bennett et al. (2019), with 42 recognised subfamilies and includes recent changes to the subfamily-level classification, in particular, the division of the Cryptinae sensu lato into the three subfamilies Ateleutinae, Cryptinae and Phygadeuontinae (Santos 2017) and recognition of the subfamily Neorhacodinae (Bennett et al. 2019). Furthermore, following Klopfstein et al. (2019), the Theroniini is recognised as a tribe of the subfamily Pimplinae, Pseudorhyssa is listed under Pimplinae and Hemiphanes under Cryptinae.

Data resources
The present checklist comprises 3,644 species of Ichneumonidae for Germany (Suppl. material 1), including 379 species that were added from the published literature since the checklist by Klaus Horstmann (Horstmann 2001a) and 48 species that are here reported from Germany for the first time (Table 1). Several recent studies, examining phylogenetic relationships amongst subfamilies within the Ichneumonidae, led to changes to the internal classification of the family (e.g. Santos 2017, Bennett et al. 2019, Broad et al. 2018, Klopfstein et al. 2019. Table 2 includes (1) species hereby added to the German fauna, (2) newly-recorded species and (3) species listed under a different name (e.g. synonyms) or species with a different systematic position in Horstmann (2001a).  Porizon albistriae (Horstmann, 1987) H In Horstmann (2001a as Phaedroctonus albistriae (Horstmann, 1987) Porizon humuli (Horstmann, 1987) H In Horstmann (2001a) as Phaedroctonus humuli (Horstmann, 1987) Porizon moderator (Linnaeus, 1758) H In Horstmann (2001a) as Phaedroctonus moderator (Linnaeus,

Discussion
The first checklist of Ichneumonidae for Germany was presented by Horstmann as part of the "Verzeichnis der Hautflügler Deutschlands" (Dathe et al. 2001). An essential prerequisite for preparing the checklist was the presence of the comprehensive "Taxapad" database that became available in 1999. The database had been continuously updated, with the most recent version released in 2015 (Yu et al. 2016).
Klaus Horstmann initially hesitated with compiling the checklist because of the daunting task and because, in his opinion, a scientifically satisfactory checklist could not be achieved (Horstmann 2002a). The main reason for his scepticism was based on the fact that there was a huge discrepancy between the extremely large number of species and a few specialists working on the family. As an example, he noted that, for the compilation of the checklist of German Sphecidae, 32 specialists were responsible for 247 species, whereas for the 3,332 species of Ichneumonidae, only one specialist was available (Horstmann 2002a). Due to the limited capacity, it was impossible to validate the status of each and every species and, to the present day, many species of Ichneumonidae, in particular, species in genera of the subfamilies Banchinae, Campopleginae, Phygadeuontinae, Ctenopelmatinae and Ichneumoninae, are poorly defined and their identification remains most challenging.
Using the comprehensive keys in Schmiedeknecht (1936) or other keys published in older literature, many of the taxonomically problematic species can somehow be 'identified', but, as Horstmann (2002a) states, it can be assumed with some confidence that many names in the faunistic literature are based on misidentifications and it is estimated that between 10 and 20% of names mentioned in faunistic publications were incorrectly identified (Yu and Horstmann 1997). Horstmann (2002a) noted that the rate of misidentifications is higher with species that usually represent the most interesting parts of a faunistic treatment, i.e. species that are rare and/or difficult to identify.
With these limitations in mind, Horstmann followed a set of rules when preparing the checklist. First and foremost, only original records were considered for compiling the checklist. Faunistic records were excluded if they were suspected to be based on misidentifications, if they were based on varieties of a particular species or if their collecting locality was unclear. For example, species that were recorded from Germany before WWII without giving the exact locality might be extralimital and were, therefore, not included. Species were excluded if the original description was published before 1945 and the species never treated in a taxonomic revision or mentioned in the taxonomic literature after that year. Finally, species were excluded if their records were based on males from genera where males are virtually impossible to identify or genera where males had not been associated with conspecific females. Only in a few cases were these species included on a case by case basis (Horstmann 2002a, Dathe et al. 2001. Species were included if they are still regarded as valid names and the type locality is in Germany.
The present checklist basically follows the same rationale. Species that were added to the current checklist are based on records of reliably identified specimens in the taxonomic and faunistic literature. In a few cases, species not included in Horstmann's checklist were added, based on a recent critical evaluation of the species or the literature source.
The catalogue of Ichneumonidae Horstmann 1997, Yu et al. 2016) lists 4,121 species for Germany, a figure that is considerably larger than the number of species in the current checklist. This is partly due to the fact that the catalogue also includes fossils. At the time when Horstmann prepared his checklist, the catalogue listed 3,898 species from Germany, of which 741 were excluded due to the aforementioned reasons (Horstmann 2002a). It is estimated that the presence of about 10% of the species in Germany requires confirmation, partly due to undetected synonymies and, to a much larger extent, because of misidentifications (Horstmann 2002a). Although the status of a number of species could be confirmed for Germany since the last checklist was published, the percentage of species requiring confirmation is probably not much different from the figure given by Horstmann (2002a). On the other hand, even the updated checklist does not include all species occurring in Germany and it is estimated that about half of them are species that are known, but have not been recorded in Germany and the other half represents species that have not yet been formally described.
Townes (1969) estimated that, for the Western Palearctic Region, about 30% of the species of Ichneumonidae are still undescribed. For Germany, this percentage is probably lower, but, assuming that 15-20% or even up to 30% of the German species are undescribed, the estimated number of species occurring in Germany ranges from 4,000 to 4,500 species. Most of these are species in genera with large numbers of undescribed species, including Campoplex Gravenhorst, Diadegma Förster, Lissonota Gravenhorst, Olesicampe Holmgren, Phygadeuon Gravenhorst and Stenomacrus Förster (Horstmann 2002a).
Twenty years after the last checklist was published, the present checklist raises the number of Germany species of Ichneumonidae by 312 species or about nine percent. Closing the gap between the currently-known species and a complete inventory of German species will require substantial efforts in terms of collecting, specimen processing and taxonomic research, but the application of integrative taxonomic approaches that combine independent character systems, including morphology, DNA sequence data and host information, hold promise of expediting the discovery of new species of Ichneumonidae in Germany and the clarification of their taxonomy and biology.