Marion Kotrba’s research while affiliated with Zoologische Staatssammlung München and other places

Among species of the spear-winged flies (Lonchopteridae) there is remarkable variation in sperm size, with some species producing giant spermatozoa. With a length of 7500 μm and a width of 1.3 μm the spermatozoon of Lonchoptera fallax ranks among the largest known to date. In the present study body size, testis size, sperm size, and spermatid number per bundle and per testis were examined across 11 Lonchoptera species. Results are discussed in terms of how these characters are related with each other and how their evolution affects the resource allocation amongst spermatozoa. Based on some discrete morphological characters and a molecular tree derived from DNA barcodes a phylogenetic hypothesis of the genus Lonchoptera is proposed. The occurrence of giant spermatozoa in Lonchopteridae is compared to convergent occurrences reported in other taxa.

531 genetic clusters (BINs) of gall midges were retrieved in a single Malaise trap that was set up in 2017 within the inner-city premises of the Bavarian State Collection of Zoology in Munich, Germany. Although the sample obtained from this trap is very limited in time and space, the number of detected BINs correspond to 63.5 % of the number of Cecidomyiidae species known in Germany up to date. Based on data collected from our utterly limited sample, and taking the variety of yet unexplored habitats into account, we conclude that Germany's fauna of gall midges must comprise considerably more species than previously expected.

Lonchoptera lutea males produce giant spermatozoa that are more than 2000 μm long and 1.4 μm wide. Unlike the typical brachyceran spermatozoon, they have a highly asymmetrical cross-section with only a single, albeit very large, mitochondrial derivative and a pair of massive accessory bodies, one of which extends throughout the entire length of the sperm tail. The accessory bodies consist of an electron-dense matrix in which numerous peculiar electron-lucid substructures are embedded. In the mated female, the giant spermatozoa are found inside two tubular spermathecae which are also extremely long, measuring 4000 μm or more.

The progress in constructing a DNA barcode library for German Diptera as published by Morinière et al. (2019, Mol. Ecol. Resour. 19: 900-928) is appraised from a dipterists' perspective. The coverage of the diversity of German Diptera in terms of barcode index numbers (BINs) and identified barcodes is analysed and visualized in simple diagrams. The influence of the project setup, methodology and/or systematic effects on the emerging numbers and trends is elucidated and extensively discussed. In addition, the documentation on the species identification methods in the database is assessed. Based on this evaluation, four ways for improving the future development, utility and reliability of this DNA database and similar projects in general are identified: (1) Sample the collections of experts. This results in a greater and more reliable coverage within a limited time frame, as opposed to random collecting and relying on a posteriori identification. (2) Give priority to medically, agriculturally or ecologically important families. Addressing these gaps will meet the most pressing needs of the community and serve as a good advertisement for the usefulness and wide applicability of the DNA barcode library. (3) Allocate resources to recruiting established experts as opposed to trainees. The fact that half of the recovered BINs remained unidentified mostly results from the insufficient involvement of experts (and expert time). (4) Appropriately document the morphological identifications by experts in the database. This will allow to assess the reliability of DNA-based identifications and to prioritize conflicting identifications within a BIN accordingly.

The internal female genitalia of 22 species of Aulacigaster are studied, covering all species groups as defined by Rung and Mathis (Smithson. Contrib. Zool., 633, 1–132, 2011). The method of embedding freshly dissected material in polyvinyl lactophenol with an admixture of chlorazol black E is far superior to results achieved by maceration in potassium hydroxide and allows the detection of delicate structures previously unnoticed. A general description of the internal female genitalia introduces all relevant structures and their variation within the genus. Establishing the presence and the multi-chambered condition of the ventral receptacle in Aulacigastridae constitutes a major result. Another important finding pertains to the presence of a ventral sclerotized ring in the posteroventral wall of the vagina, which had not been described in Aulacigastridae before. The variable characters are coded across the studied species and are subjected to a phylogenetic analysis in combination with the character set of Rung and Mathis (Smithson. Contrib. Zool., 633, 1–132, 2011). The resulting topology is used to reconstruct ancestral character states and to discuss intrafamilial character state changes at and above the species group level. Information extracted from the internal female genitalia corroborates and adds resolution to the results of previous analyses that employed characters of the external morphology and the male terminalia. Brief per species descriptions and additional illustrations are placed in the electronic supplementary material.

Braula coeca has been reported repeatedly, but incorrectly, to have only a single spermatheca—an extremely rare condition in the higher flies. This error is based on the misinterpretation of the ventral receptacle as a single spermatheca combined with the failure to detect the two present but largely reduced dorsal spermathecae. This misconception is of importance, e. g., for correct character coding in phylogenetic analyses and in the context of studies regarding recurrent trends in the evolution of the spermathecae and the ventral receptacle. The ventral receptacle of B. coeca is described and illustrated in detail together with other aspects of the female reproductive tract.

Piophila casei has been reported repeatedly, but incorrectly, to have only a single spermatheca—an extremely rare condition in the higher flies. This error is based on the misinterpretation of the large sclerotized ventral receptacle as a single spermatheca combined with the failure to detect the two present but unsclerotized spermathecae. This misconception is of importance not only in the context of studies regarding recurrent trends in the evolution of the ventral receptacle. It also led to a set of erroneous character codings in a phylogenetic analysis of the family. To set the records straight, previous more accurate literature is revisited and the ventral receptacle of Piophila casei is described and illustrated in detail together with other aspects of the female reproductive tract such as the spermathecae, accessory glands, vagina, and anterior ventral vagina pouch.

The internal female genitalia of Episyrphus balteatus (De Geer , 1776) are described morphologically and histologically. Special emphasis is placed on the description of what is called here the ventral circular structure (vcs), a newly discovered small but distinctive structure situated ventrally opposite to the opening of the spermathecal ducts. A comparative study of representatives of all major clades of Syrphidae revealed the vcs to belong to the ground plan of the family. Its potential function and uncertain phylogenetic origin are discussed.