Hans Pohl

Natural history collections house material from centuries of collecting efforts. In the Phyletisches Museum Jena (PMJ), ca. 1 Mio specimens are deposited, some of them dating back as far as the 17 ^th century. Modern imaging techniques have the potential to gain new insights from this historical material. However, a large part of the PMJ insect collection has not been revised by scientists in recent times. We screened the entire Auchenorrhyncha collection and found several specimens parasitized by two different species of the genus Halictophagus (Halictophagidae, Strepsiptera) that had previously been overlooked. These historical findings represent the only evidence to date of the occurrence of these two species in Germany and therefore suggest, at least historically, a larger distribution area than was previously known. In addition, hitherto unknown females and primary larvae were morphologically documented using state-of-the-art techniques such as synchrotron-radiation-based X-ray µCT and scanning electron microscopy. The data generated in this study cover the field of collectomics and can be seamlessly used as a basis for the emerging discipline of museomics. In taxonomic and systematic research and in the context of environmental change, pinned insects may play an outstanding role in the near future, as their DNA is not damaged by formalin fixation and thus can yield remarkable results even after more than 100 years. Our results underpin the value of historical material for modern research questions, especially for species that are difficult to find in nature.

The biology of holometabolan larvae, which are often the main feeding stage, is extremely diverse. Phytophagy plays a significant role in basal hymenopteran groups, in Lepidoptera, and in megadiverse groups of polyphagan beetles. A switch to parasitoidism was a major evolutionary shift in Hymenoptera. Predaceous habits are generally found in Neuropterida, in various groups of Coleoptera, and in some trichopterans. Wood and fungi play an important role in Archostemata and several groups of polyphagan beetles, as well as in some groups of Hymenoptera and Diptera. Two main trends can be observed in larvae of megadiverse holometabolan groups: enormous morphological diversification as in Coleoptera or alternatively morphological simplification and uniformity as in the hymenopteran Apocrita and the dipteran Brachycera. The ability of larvae to use food sources and microhabitats different from those used by adults has likely contributed to the evolutionary success of holometabolan lineages.

Four new species of Strepsiptera from the genus Deltoxenos Benda, Pohl, Nakase, Beutel & Straka (Xenidae) are described based on the female cephalothoraces. These include the first Deltoxenos species from the Indomalayan and Australasian regions. New host species and genera for Xenidae – Phimenes solomonis (Vecht, 1959) and Pareumenes quadrispinosus (Saussure, 1855) – are recorded as strepsipteran hosts for the first time. Diagnoses and descriptions of female cephalothoraces are presented for all four newly described species of Deltoxenos, with brief diagnoses for Deltoxenos bidentatus Pasteels, 1950 and Deltoxenos rueppelli Kinzelbach, 1971. The known distribution of D. bidentatus and D. rueppelli are significantly expanded, and a notably broader host range documented for the latter. Diagnostic characters and geographic distribution are discussed in the context of a recent long-range dispersal event from Afrotropics to the Australasian region.

Females of the insect order Strepsiptera are known to be traumatically inseminated. Traumatic insemination is the process of insemination by sperm transfer through a wound inflicted by the male in the female's integument, rather than by the male transferring sperm through the female's genital opening. Females fertilised by traumatic insemination are likely to exhibit morphological adaptations that help them to reduce the fitness costs associated with the integument wounding. One such adaptation is the presence of a paragenital organ. It has been described in traumatically inseminated bugs of the superfamily Cimicoidea and in species of the Strepsiptera genus Stylops . Although the paragenital organ appears to play a critical role in the mating biology of Stylops species, its phylogenetic roots are unknown. Here, we show that the paragenital organ in Strepsiptera may be an autapomorphy of the family Stylopidae, where we found it present in all species of the genera we studied (i.e., Eurystylops , Halictoxenos , Hylecthrus , Kinzelbachus ). Our data thus refute the notion that the paragenital organ in Strepsiptera is exclusive to the genus Stylops . Integument relative thickness assessment based on µCT data revealed that regardless of the presence of a paragenital organ in Strepsiptera, penetration sites in the female's integument are thickened relative to control sites. In addition, we found evidence for the lateral processes of the secondary larval exuvia stabilising the paragenital organ. Our study contributes to the basic understanding of the evolution and the function of the paragenital organ in Strepsiptera and suggests potentially important morphological characters for a species‐level phylogeny of the Stylopidae.

Two new species of Strepsiptera from the genus Zethus Fabricius, 1804 (Hymenoptera: Vespidae) are described. Although the stylopisation of the genus Zethus has been known for almost a century, we provide the first description of its strepsipteran parasites. Zethus brasiliensis fuscatus R. Bohart & Stange, 1965 is parasitised by Eupathocera zethisp. nov. in the Neotropical Region (French Guiana) and Zethus favillaceus Walker, 1871 by Deltoxenos impressussp. nov. in the Afrotropical Region (Kenya). An independent switch to the same host genus is supported by molecular and morphological data. Diagnoses and detailed descriptions of the species are provided based on characters of the female cephalothorax and male cephalotheca. Diagnostic characters are discussed.

Although the knowledge of the skeletal morphology of bees has progressed enormously, a corresponding advance has not happened for the muscular system. Most of the knowledge about bee musculature was generated over 50 years ago, well before the digital revolution for anatomical imaging, including the application of microcomputed tomography. This technique, in particular, has made it possible to dissect small insects digitally, document anatomy efficiently and in detail, and visualize these data three dimensionally. In this study, we document the skeletomuscular system of a cuckoo bee, Thyreus albomaculatus and, with that, we provide a 3D atlas of bee skeletomuscular anatomy. The results obtained for Thyreus are compared with representatives of two other bee families (Andrenidae and Halictidae), to evaluate the generality of our morphological conclusions. Besides documenting 199 specific muscles in terms of origin, insertion, and structure, we update the interpretation of complex homologies in the maxillolabial complex of bee mouthparts. We also clarify the complicated 3D structure of the cephalic endoskeleton, identifying the tentorial, hypostomal, and postgenal structures and their connecting regions. We describe the anatomy of the medial elevator muscles of the head, precisely identifying their origins and insertions as well as their homologs in other groups of Hymenoptera. We reject the hypothesis that the synapomorphic propodeal triangle of Apoidea is homologous with the metapostnotum, and instead recognize that this is a modification of the third phragma. We recognize two previously undocumented metasomal muscle groups in bees, clarifying the serial skeletomusculature of the metasoma and revealing shortcomings of Snodgrass' “internal–external” terminological system for the abdomen. Finally, we elucidate the muscular structure of the sting apparatus, resolving previously unclear interpretations. The work conducted herein not only provides new insights into bee morphology but also represents a source for future phenomic research on Hymenoptera.

Polyandry, the practice of females mating with multiple males, is a strategy found in many insect groups. Whether it increases the likelihood of receiving beneficial genes from male partners and other potential benefits for females is controversial. Strepsiptera are generally considered monandrous, but in a few species females have been observed copulating serially with multiple males. Here we show that the offspring of a single female can have multiple fathers in two Strepsiptera species: Stylops ovinae (Stylopidae) and Xenos vesparum (Xenidae). We studied female polyandry in natural populations of these two species by analysis of polymorphic microsatellite loci. Our results showed that several fathers can be involved in both species, in some cases up to four. Mating experiments with S. ovinae have shown that the first male to mates with a given female contributes to a higher percentage of the offspring than subsequent males. In X. vesparum, however, we found no significant correlation between mating duration and offspring contribution. The prolonged copulation observed in S. ovinae may have the advantage of reducing competition with sperm from other males. Our results show that monandry may not be the general pattern of reproduction in the insect order Strepsiptera.

As the only direct records of the history of evolution, it is critical to determine the geological source of biota-bearing fossils. Through the application of synchrotron-radiation micro-computed tomography (SR-µ-CT), Fourier-transformed infrared-spectroscopy (FT-IR), visual evaluation of ultraviolet fluorescence (UV-VS), radiocarbon dating (¹⁴C quantification), and historical sleuthing, we were able to identify and sort 161 (83 Baltic amber, 71 Copal and 7 Kauri gum pieces) individually numbered and largely mislabeled pieces of East African Defaunation resin (~145 years old) and copal (~390 years old), as well as Baltic amber (~35 million years old) from the Phyletisches Museum collection. Based on this collection, we define two new species: ‡Amphientomum knorrei Weingardt, Bock & Boudinot, sp. nov. (Psocodea: Amphientomidae, copal) and †Baltistena nigrispinata Batelka, Tröger & Bock, sp. nov. (Coleoptera: Mordellidae, Baltic amber). For selected taxa, we provide systematic reviews of the fossil record, including: Amphientomidae, for which we provide a key to all species of Amphientomum, extant and extinct, and recognize the junior synonymy of Am. ectostriolatum Li, 2002 (an unjustified emendation) under Am. ectostriolate Li, 1999 (syn. nov.); the fossil ant genus †Yantaromyrmex and the clades Dorylinae, Plagiolepidini, Camponotus, Crematogaster, and Pheidole (Formicidae); the Nevrorthidae (Neuroptera); and Doliopygus (Coleoptera: Curculionidae: Platypodinae). We synonymize Palaeoseopsis Enderlein, 1925 with Amphientomum Pictet, 1854, syn. nov. and transfer one species from Amphientomum, forming Lithoseopsis indentatum (Turner, 1975), comb. nov. To prevent the uncritical usage of unidentifiable fossils attributed to Camponotus for macroevolutionary analysis, we transfer 29 species to the form genus †Camponotites Steinbach, 1967, which we consider to be most useful as incertae sedis in the Formicinae. We treat †Ctt. ullrichi (Bachmayer, 1960), comb. nov. as unidentifiable hence invalid stat. nov. We also transfer †Ca. mengei Mayr, 1868 and its junior synonym †Ca. igneus Mayr, 1868 to a new genus, †Eocamponotus Boudinot, gen. nov., which is incertae sedis in the Camponotini. Concluding our revision of Camponotus fossils, we transfer †Ca. palaeopterus (Zhang, 1989) to Liometopum (Dolichoderinae), resulting in †L. palaeopterumcomb. nov. and the junior synonymy of †Shanwangella Zhang, 1989, syn. nov. under Liometopum Mayr, 1861. Because the type specimens of the genera †Palaeosminthurus Pierce & Gibron, 1962, stat. rev. and †Pseudocamponotus Carpenter, 1930 are unidentifiable due to poor preservation, we consider these taxa unidentifiable hence invalid stat. nov. To avoid unsupported use of the available fossils names attributed to Crematogaster for divergence dating calibration points, we transfer three species to a new collective taxon that is incertae sedis in Myrmicinae, †Incertogaster Boudinot, gen. nov., forming †In. aurora (LaPolla & Greenwalt, 2015), †In. praecursor (Emery, 1891), comb. nov., and †In. primitiva (Radchenko & Dlussky, 2019), comb. nov. Finally, we transfer †Ph. cordata (Holl, 1829) back to Pheidole, and designate a neotype from our copal collection based on all available evidence. All new species plus the neotype of ‡Ph. cordata are depicted with 3D cybertypes from our µ-CT scan data. We introduce the convention of a double dagger symbol (‡) to indicate fossils in copal or Defaunation resin, as these may yet be extant. To further contextualize our results, we provide a discussion of amber history and classification, as well as the Kleinkuhren locality, to which multiple specimens were attributed. We conclude with conspecti on key biological problems and increasing potential of µ-CT for phylogenetic paleontology.

A new species of Strepsiptera of the genus Paraxenos Saunders, 1872 (Xenidae) from the United Arab Emirates is described. It was recorded from the host species Bembix kohli Morice, 1897 and represents the first occurrence of Paraxenos from Bembix Fabricius, 1775 in the Afrotropical region. A detailed redescription of the female cephalothorax of Paraxenos hungaricus (Székessy, 1955) is provided, together with the first description of the male cephalotheca. The holotype of Paraxenos krombeini Kifune & Hirashima, 1987 was redescribed. Additionally, a key for parasites of Bembix among Paraxenos species is provided based on characters of the female cephalothorax and male cephalotheca. The distribution and conservation status of Paraxenos spp. on Bembix are also discussed.

Traumatic insemination refers to mating in which males pierce the female’s integument with his penis for insemination. Strepsiptera are often listed as an example for this mode of copulation. However, while traumatic insemination in Mengenillidae with free-living females is undisputed, its occurrence in Stylopidia with permanent endoparasitic females – 97% of the known species of Strepsiptera – has remained unclear. Rather, observations from a single study on Xenos vesparum (Xenidae) that questioned traumatic insemination in this species became generalized for Stylopidia. Here we show that integration of data from various imaging methods provides convincing evidence for traumatic insemination being phylogenetically widespread in Strepsiptera. Specifically, we provide the first evidence of injury wounds from traumatic insemination in species of Mengenillidae, Corioxenidae, Elenchidae, Halictophagidae and Xenidae. Using three-dimensional models of copulating pairs of Stylops ovinae (Stylopidae) and X. vesparum, we visualize the physical piercing of the female’s integument by the male’s penis. Finally, we show in species of Mengenillidae, Xenidae and Stylopidae that traumatic mating is associated with the injection of sperm in the female’s haemocoel. Our results significantly alter the understanding of the reproductive biology of Strepsiptera and imply that traumatic insemination has been the ancestral mode of copulation and retained in most, if not all, extant families.