GBOL III: Dark Taxa will target the part of the German fauna that is still largely unknown, the so-called “Dark Taxa”. There are unknown and unstudied taxa in several taxonomic groups. Within GBOL III: Dark Taxa we will specifically tackle the Diptera (flies & midges) & the parasitoid Hymenoptera (parasitoid wasps) that together comprise about one quarter of the German Fauna.

Proportion of the German fauna of Dark Taxa in Diptera and Hymenoptera

The parasitoid wasps are one of the least known groups among insects, and even entomologists sometimes struggle to name or recognize some of the most important groups. Many are truly „Dark Taxa“.

Parasitoid wasps are incredibly diverse. There are thousands of species in central europe and maybe millions worldwide. All parasitoid wasps – except for a few subgroups that returned to a phytophygous lifestyle – develop on or in other arthropod taxa, mostly insects, thereby killing the host, in contrast to a „parasite“. Diversity, abundancy, and the close link to other taxa make them crucial in our understanding of ecosystems and in our understanding of the evolution of biodiversity. Furthermore, they are important for proper conservation of biotopes and species, for which they so far have always been fully neglected. Finally, the hold some economically important roles as antagonists of pest species and as biological control agents, as pollinators and as a largely unwritten pharmacopoeia. When magnified, parasitoid wasps are fascinating and often appear agile and charismatic. They are diverse not only in species but also in morphology and life history. Among parasitoid wasps, you will find the smallest of all insects as well as large-bodied colorful forms. You will find the strangest and most beautiful creatures and even after decades of work on parasitoid wasps you will encouter some new striking wasps that you have never seen before.

Flies, mosquitoes, midges and gnats belong to the order Diptera (Insecta) and they all have only two membraneous wings adapted to fly (“Di”- meaning two and “ptera” meaning wings). The second pair of wings have been modified during the evolution of the group into small flight stabilizing organs called halters. Diptera are traditionally divided into two major groups called Brachycera and “Nematocera” or “Lower Diptera”.

The “Nematocera” is a paraphyletic group that comprises several evolutionary lineages, including mosquitoes, midges, gnats and relatives. Morphologically they are easy to recognize as adults have elongated multi-segmented antennae, and larvae have a complete, well-developed cephalic capsule with mandibles. “Lower Diptera” have a worldwide distribution and are common and numerous in many ecosystems. Their larvae range from fully aquatic to fully terrestrial and they are often detritus or filter feeding, but can also be predatory or saprophagous. Adults usually do not feed at all or only take up water, but some groups also live on plant material, such as nectar or pollen or suck on blood of vertebrates (e.g. mosquitoes). Because of their extremely wide range of larval and adult habitats, they play important roles in maintaining ecosystem services, such as decomposition of organic material (saprophagous larvae), biological control agents and to balance natural populations (predatory larvae), pollination (adults), and also as a food source for other predators.

“Lower Diptera” are often put aside and not studied by taxonomists due to their small to minute size, their fragility and their scarcity of external morphological diagnostic characters. In GBOL III we want to bring more light in the “Lower Diptera” taxonomy with a new generation of taxonomists for these groups. Therefore five out of the six PhD projects that deal with a family of Diptera are focused on ”Lower Diptera”, namely on Limoniidae, Psychodidae, Chironomidae, Sciaridae and Cecidomyiidae.

The family of gall midges (Cecidomyiidae) comprises species whose larvae are either fungus eaters (mycophages), plant eaters (phytophages) or predators; mycophagy is the ancestral, phytophagy (including gall-inducing) possibly the most common mode of feeding. Five of the six subfamilies are regarded as universally mycophagous. This family is a dark taxon par excellence: we do not even approximately know how many species there are extant in the world (estimations range from 20,000 to 2 million) and, of most of the 6,500 species named, only little is known about the morphology, and merely fragments about the biology and distribution. Previously, the plant eaters were believed to be the most species-rich group, but recent studies (mostly in Sweden) suggest the number of fungus eaters being larger, at least in the temperate parts of the Northern Hemisphere (and the number of predators having been grossly underestimated in the past). This may be expected to be true for the German fauna as well, although the available data seem to suggest otherwise. Realistically, we may expect the presence of 2,500 different cecidomyiids in Germany, which means that two thirds of the species total are not yet recorded―the 930 BINs identified so far point in exactly that direction. The task of GBOL III: Dark Taxa is, regarding the Cecidomyiidae, a most challenging one, not made easier by the fact that at least half of the species that may be anticipated to occur must be rated as “rare”.

Chironomids (nonbiting midges) are a diverse and economically important group of nematoceran flies. As the larval stages inhabit aquatic or semi-aquatic habitats, many species are important indicator organisms e.g. for assessing the water quality. Furthermore, larvae and pupae serve as an important food source for other aquatic organisms. Despite their world-wide distribution, species-richness (estimates predict well over 10.000 species) and high abundance, the identification of these insects is notoriously difficult. The rearing of adult males or cytogenetic analyses of their chromosomes is usually required for correct identification, and often, morphologically distinct groups comprise several very similar or identical cryptic species.

The Empidoidea are a mostly predatory group of flies whose larvae and adults attack other insects. This predatory nature makes these flies especially interesting as they play an important role in pest control as natural enemies of pest insects. Over 10,000 species are documented worldwide, of which 10% are found in Germany. Although this group has been subject of various phylogenetic studies (e.g., Wahlberg & Johanson 2018), the taxonomy at the species level is still largely unresolved. The Empidoidea are morphologically extremely diverse, ranging from 1 to about 15 mm in length.

Fungus gnats of the family Keroplatidae are primarily forest dwellers found in the damp habitats favored by their host fungi. Distributed worldwide, they are most common in the more tropical, moist regions but can be found in a variety of ecosystems. Adults are mostly found in dark, damp places, sometimes in caves, and their flight is slow and their habits are mostly crepuscular or nocturnal. Larvae also inhabit damp, dark places including caves, bamboo internodes, and deeply hollowed cavities under stones or fallen trunks. Larvae can be predaceous or mycophagous (feed on fungi), and some have luminescent larvae known as “glow worms”. There are exceptions like the larvae of Planarivora insignis, a Tasmanian species, that live endoparasitically in land planarians, but the biologies of the larvae of most other genera are still unknown. A total of 62 species have been reported from Germany (Kallweit & Plassmann 1999; Schumann 2002, 2005), but only half have been successfully DNA barcoded in GBOL and a fifth of the barcoded specimens have no species name yet. In the ZFMK collections there are more than 2400 keroplatid specimens as result of the field campaigns of GBOL I and II. The group deserves a taxonomic review for Central Europe with the implementation of DNA barcoding.

Pediciidae or hairy-eyed crane flies is a member of the Tipuloidea, together with living families Cylindrotomidae, Limoniidae, and Tipulidae. Pediciids are relatively large, long-legged mosquito-like flies with an elongated abdomen. Adults mostly live in shaded, damp places, close to the habitats (mostly bodies of water) in which their larvae develop. Larvae of this family are quite diverse in their way of life, with some species feeding on fungi in partially decomposed dead wood in forests, but most other species live in or on the banks of water bodies feeding on fallen leaves and other soft, partially decomposed plant remains. Pediciidae is not a large family (37 species in Germany; see Schumann et al. 1999; Schumann 2010), but is underrepresented in GBOL database, with only 12 barcoded species. DNA barcoding and a taxonomic revision of the family will aim to make species of this family easily diagnostic in order to facilitate the study of their ecology and natural history.

Limonia nubeculosa – picture: wikimedia commons

Limoniidae, together with the three other families of Tipuloidea (i.e., Tipulidae, Pediciidae and Cyclindrotomidae), are commonly known as crane flies. They are one of the most “primitive” evolutionary lineages of the order Diptera (Jong 2017). Limoniidae are arguably the most diverse dipteran family, with more than 10,525 described species world-wide (Jong 2017, Brown 2009, Oosterbroek 2020). Most of their larvae are plant-feeders on rotting vegetable matter, algae, mosses, mushrooms, etc., but larvae of some special groups (subfamily Limnophilinae) are predators on other small invertebrates and worms. Larval stages of Limoniidae have a very important ecological service as organic matter decomposers (partly relevant as indicators within EU Water Framework Directive [2000/60/EC]), and adults may constitute important food sources for birds, other vertebrates, spiders and predaceous insects (Gelhaus 2009). Identification keys to western Palaearctic/European Limoniidae are incomplete, or outdated, or unfinished, or covering only smaller parts of the continent, or a combination of the previous. There is no comprehensive, accurate work that covers our current knowledge of the group. With 292 recorded species (Oosterbroek 2020), Germany holds more than half of the diversity of this family in Europe (some 70 genera and ca. 560 species; Oosterbroek 2015). Efforts for DNA barcoding the fauna of Germany in GBOL I and II (2012-2018) resulted in 1,078 studied specimens, but only 601 DNA barcodes representing 89 species (a bit less than 1/3 of the German fauna of Limoniidae). Thus, one of the aims of GBOL III is to create a comprehensive DNA barcode database for Limoniidae and to provide updates on the taxonomy of the family.

Phoridae are one of the most diverse and abundant families of Diptera, with over 4,300 valid species worldwide and about 400 species recorded from Germany. They are currently outnumbered only by the Syrphidae in number of described species in the Lower Cyclorrhapha. The genus Megaselia alone contains over 1,600 species worldwide and over 250 species in Germany, with estimates of true diversity ranging between 10 and 20 thousand species worldwide. Phoridae are importantly one of the most ecologically diverse groups of Diptera, contributing to ecosystem balance as decomposers, herbivores, predators, parasitoids and true parasites. Phoridae are also among the most abundant Diptera in Malaise trap samples. Compared to most brachyceran families, their diversity is high and poorly documented with a comparably low number of taxonomic experts. A recent example of the abundance and hidden diversity of phorids is the trapping in urban Los Angeles, during a single year, of over 42,000 specimens belonging to 99 species, 43% of which were new to science. Recent findings in Denmark show that similar rates of species discovery can be expected also in central northern Europe. Existing keys cover only a small proportion of this diversity, and therefore the identification of species, particularly in morphologically uniform genera, can be greatly aided by morphometrics and DNA barcoding. In this project, we will use integrative taxonomy to document the biological and morphological diversity of German Phoridae and of the genus Megaselia in particular, using DNA mini-barcodes and barcodes to discover new species and define morphological barcodes. Rates of discovery for new species are hard to determine due to lack of recent efforts in continental Europe on this group; there are dozens of potentially new species even in well studied areas. Species composition and diversity will be compared across different sampling sites and habitat types in Germany.

Megaselia scalaris

Moth flies (Diptera: Psychodidae) are small nematoceran dipterans (insects with two wings), which are easily recognizable because they possess a densely-haired vestiture and many of them hold their wings at rest horizontally over the abdomen, giving them the appearance of small moths; hence the common name “moth flies”. Adults have erratic and weak flights, and they have managed to invade a wide variety of habits from high montane streams to very contaminated drains. Their larvae, however, can be found in several habitats such as rotting wood, carrion, fungi, dung, and soil. The family has around 2,900 described species so far and there are many known undescribed species. Despite their world-wide distribution and the fact that some of them are vectors of diseases, being so small and hard to collect makes them a very neglected and understudied group among the Diptera. Many different classifications for this family have been proposed during the years, and its intrafamilial relationships are still under debate. In Europe this family is thoroughly studied with almost 500 recorded species, and many new species have been described in recent years. Nevertheless, several countries lack systematic collections and sampling efforts, which makes difficult to know the species distribution; many species are known by only one sex; the majority of the species lack the description of larval stages and there are a few species with DNA barcodes available. In sum, moth flies are a very understudied group, also called “dark taxa”, and the aim of GBOL III is to update their taxonomy and systematics.

Lepidiella matagalpensis – picture: S. Jaume Schinkel
Bradysia bicolor

Sciaridae are one of the most diverse lineages of Diptera Nematocera, with over 3,000 species worldwide and about 350 species so far recorded from Germany. However, data from global DNA barcoding efforts indicate that the true global diversity of the family could be between 10,000 and 100,000 species. Sciaridae are primary decomposers of plant and fungal matter in soil and dead wood. Being abundant, species rich and easy to monitor by Malaise traps, Sciaridae are potentially superior to any other taxon as indicators of habitat quality. Some species can be of economic importance as pests of commercially grown plants and mushrooms in greenhouses. Sciaridae are among the most abundant insect families in Malaise trap samples, often with thousands of specimens. Their diversity is high and relatively poorly documented also in temperate zones and the number of taxonomic experts is low in comparison to species numbers, which has prevented them from being used in ecological studies. The most reliable characters for morphological species identification are the male genitalia, but the taxonomic coverage of available keys is still largely incomplete. DNA barcoding has proved to be an essential tool for discovery of cryptic species. In this project, we will use integrative taxonomy to document the biological and morphological diversity of German Sciaridae, using DNA barcodes to discover new species and define morphological barcodes. The project will explore the potential of Sciaridae as indicators of habitat quality (soil, woodland) in ecological studies and produce information sheets for pest species of economic importance in Germany.

The Chalcidoidea is one of the largest groups of parasitoids wasps, with currently about 22,000 described species and estimates ranging up to 500,000 species worldwide. Their taxonomy is highly problematic because original descriptions are often poor and not diagnostic, and identification keys are available for only a few groups. Probably less than 5% of the described species can be named without comparing to the type specimen. In Germany, about 750 species of Aphelinidae, Eulophidae, Encyrtidae have been recorded, but many more species are expected to exist. The knowledge of the biology is lacking for the majority of chalcid species and often based only on relatively few representative species, despite their important role in the balance of terrestrial ecosystems through their ability to regulate populations of plant feeding insects. Eulophidae are mostly primary parasitoids of the larvae of Diptera and Lepidoptera, but also of Coleoptera. Aphelinidae and Encyrtidae are primarily associated with whiteflies and scale-insects (Hemiptera: Sternorrhyncha), many of which are important pest species. The Chalcidoidea include some of the most important species used for the biological control of pest insect populations

Ceraphronoidea comprises two families, with 603 valid species worldwide (Ceraphronidae: 304 spp., Megaspilidae: 299 spp.), which is just a small fraction of the true species diversity. From Germany, only 35 species (Ceraphronidae: 11 spp., Megaspilidae: 24 spp.) have been recorded, but in reality several hundred species might exist. Ceraphronidae develop as endoparasitoids, often in nematocerous Diptera, such as Cecidomyiidae. Megaspilids are ectoparasitoids of a wide range of primary hosts, including Diptera, Neuroptera, Mecoptera and Hemiptera. Some species develop as hyperparasitoids of parasitoid wasps, e.g., of Braconidae within their aphid hosts. The external morphology of Ceraphronoidea is notoriously monotonous and very few characters have been used for classical morphological species concepts (e.g., anatomical line ratios or microsculpture). The morphology of male genitalia characters has proven to be informative on the species level for Ceraphronoidea, but has never been explored for the whole group. This is because the study of ceraphronoid male genitalia is extremely difficult due to their extremely small size (100–200 µm) and therefore a functional male genitalia-based taxonomic system has never been established. The aim of the current project is to use functional morphology of male genital structures, combined with DNA-Barcoding to complement the traditional morphological datasets and verify newly established species concepts, also matching females with their male counterparts. Morphological characters will be scored with Micro-CT and Confocal Laser Scanning Microscopy (CLSM). In addition, the potential of wing interference patterns (WIPs) for species diagnoses will be explored. With this information, it will be possible to assess the species diversity of German Ceraphronoidea and to describe new species within integrative taxonomic revisions.

The Diapriidae is among the least-known families of Hymenoptera. They are diverse, often extremely abundant, and most remain unnoticed by collectors due to their small sizes of 2-3 mm in length. The German checklist lists about 290 species, but it is estimated that less than half of the species have formally been described. The last comprehensive taxonomic treatment of the group is more than 100 years old (Kieffer 1916). Very little is known about the biology of Diapriidae. These insects occur in most terrestrial habitats (with a preference for not too dry environments) and are often very diverse and abundant in insect samples that were collected using Malaise traps or yellow pan traps. Most species are solitary or gregarious endoparasitoids of Diptera larvae and pupae, though life histories for most species are unknown. Usable identification keys are available for only a small fraction of the species.

Eurytoma sp. – picture: G. Delavare

Eurytomidae belong to the superfamily Chalcidoidea and comprise 1,453 described species worldwide. For Germany, 115 species belonging to 6 genera have been recorded. Of the 6 genera, Eurytoma (67 species) and Tetramesa (33 species) are the most specious. The other genera Aximopsis, Bruchophagus, Sycophila and Systole are represented by 1, 6, 6 and 2 species. Eurytomidae includes species with a wide variety of biology, but most of them tend to be endophytic, either as phytophages or as phytophagous insect parasitoids. The family includes seed feeders, gall formers, stem miners and parasitoids. Most of the parasitoid species are primary ectoparasitoids, attacking eggs, larvae, or pupae of Coleoptera, Orthoptera, Diptera, and Hymenoptera, or hyperparasitoids, often attacking ichneumonoid primary parasitoids. Seed feeders are associated with, for example, Fabaceae, stem miners mostly with Poaceae grasses. Approximately one third of the species recorded from Germany are phytophagous, so eurytomids are diverse and abundant components of two key ecological niches in natural food webs, i.e., (specialised) herbivores and parasitoids. There are many economically important pest species in this family, for example of almond and pistachio trees and of cultivated alfalfa. In most cases, it is fairly easy to distinguish a eurytomid from other parasitoid wasp families. However, despite all attemps to improve knowledge about the family, species identification has remained problematic. The actual number of species in Germany is unknown. More than half of the species recorded belong to a single genus Eurytoma. Eurytoma species are morphologically highly similar and association of male and female specimens is often impossible. So far, there has not been any targeted action to study and include Eurytomidae in GBOL or other European biodiversity initiatives. GBOL III: Dark Taxa can be a guideline project for incorporation of this fascinating insect family into biodiversity research and conservation efforts worldwide.

Eupelmidae is a family of parasitoid wasps in Chalcidoidea. It consists of three subfamilies (Eupelminae, Calosotinae, and Neasastatinae), all of which have representatives in Germany. A total of 32 species are currently recorded from this country. Eupelmids are parasitoids of, for example, beetle larvae, spider eggs or gall wasps, i.e., they attack a broad variety of hosts. Most species show specific adaptations to the ability of powerful jumps, including a large and convex mesopleuron. By this character and others, eupelmids are usually easy to differentiate from other chalcidoids. The shared characters, however, might be the result of convergent evolution because new phylogenetic studies indicate that the family might in fact be polyphyletic.

Anastatus sp. picture: L. Fusu

The Figitidae are a family of parasitoid wasps. They are closely related to the Cynipidae, which are gall inducers on various plant species. The figitids, however, are true parasitoids. The six European subfamilies can be roughly divided by their host preferences. Three of them attack aphid antagonists: The Anacharitinae parasitize brown lacewing (Hemerobiidae) larvae, the Aspicerinae hoverfly larvae (Syrphidae) and the Charipinae are so-called hyperparasitoids on other parasitoid wasp larvae (Braconidae: Aphidiinae). The rather recently described Parnipinae are parasitoids on gall wasps but are only known from South-western Europe. By far the most diverse are the Figitinae and Eucoilinae which parasitize flies mostly in ephemeral matter such as dung, carrion or compost. Cynipoidea, the superfamily which the figitids belong to, have some shared characters that make them easy to distinguish from other wasps, for example, a distinct wing venation pattern and a laterally flattened metasoma. To separate the figitids from other cynipoids is not as straightforward as that. A close examination with adequate instruments and methods is necessary to undoubtedly identify them. A small size ranging from about 1-5mm, uniform colouration and external morphology have caused many researchers to neglect the group. By the end of the 19th century zoologists from Germany started to tackle the figitid’s diversity but the group has never been continuously worked on by a larger number of researchers. Today, about 120 species are known from Germany but according to preliminary assessments the number can be expected to be 180 species or more. Before GBOLIII: Dark Taxa, there was no designated expert working with figitids in Germany. This underlines both the characterisation of the figitids as Dark Taxa as well as the importance of the project to finally address this diverse family in a biodiversity research context.

Trybliographa sp. – picture: R. Back

Microgastrinae is worldwide distributed subfamily of braconid wasps comprising 3,000 described species. An additional 20,000-30,000 species are estimated to remain undescribed, making the Microgastrinae one of the most specious groups of parasitoid wasps. Because these insects are gregarious endoparasitoids of the caterpillars, they play an important role in integrated agriculture and forestry pest management.

Ormyrus sp. – picture: O. Niehuis

Ormyridae is a small, cosmopolitan family of parasitoid wasps in the superfamily Chalcidoidea. They are characterised by the conspicuous sculpturing of their metasomal tergites, often bright metallic colour, and well-developed hind coxae. The larvae of ormyrids are solitary idiobiont ectoparasites of various gall forming insects, mainly tephiritid flies and cynipid wasps.

About 140 species in three genera have been described worldwide, of which twenty- nine have been recorded in Europe. The genera Eubeckerella and Ormyrulus are monotypic; Ormyrus is the only speciose genus. The family has never been catalogued or revised worldwide, and a large number of species have not been described yet. The actual number of species is, thus, estimated to be much higher. In Germany, only 14 species of Ormyrus have been reported but still a reliable identification on species level is not possible. Biological data, morphological data as well as a molecular database are therefore necessary to shed light on this dark taxon.

The superfamily Platygastroidea comprises 6,095 described species in two families, Scelionidae and Platygastridae. Only 136 species have been recorded from Germany: 56 in Scelionidae and 80 in Platygastridae. The actual number of species of Platygastroidea in Germany is unknown, but there is reason to believe that several hundred species exist. Scelionidae include 3 subfamilies, all of which are egg parasitoids of insects or spiders. Scelioninae are parasitoids of Orthoptera, Mantodea, Heteroptera, Lepidoptera, Embioptera, Araneae; Teleasinae are parasitoids of Coleoptera; Telenominae are parasitoids of Heteroptera, Auchenorrhyncha, Lepidoptera, Neuroptera and Diptera. Platygastridae includes 2 subfamilies. Sceliotrachelinae are egg parasitoids of Coleoptera, Fulgoroidea, Aleyrodidae and Pseudococcidae. Platygastrinae parasitise eggs or early larval instars of Cecidomyiidae but complete development in the late larval or pupal stage of their hosts. Therefore, Platygastroidea have great economic significance, as many of their hosts are pests in agriculture and forestry. Platygastroidea are considered among the most reliable agents used in biological control and are even used as biological model organisms. Despite their importance, Platygastroidea undoubtedly comprise some of the “darkest” elements of the German insect fauna, with few incomplete and outdated keys. Many genera, especially in the Platygastrinae, are in a state of taxonomic disarray, due to an abundance of vague and insufficiently illustrated species descriptions. The aim of the current project is to apply integrative taxonomic methods, including COI barcoding, to the revision of key genera within Platygastroidea. Historical material from European museums will be cross-referenced with modern DNA voucher specimens to establish a diagnostic framework for species-level identification. With DNA barcode data and high-resolution microphotography, the platygastroid diversity of Germany will be accessible and identifiable for researchers in many fields including agriculture, ecology, evolution, biosecurity, and nature conservation.

Synopeas sp.