Insights from the past: the work of Hans von Alten on the evolution of brain structure, ecological adaptation, and cognition in hymenopteran species.

In his treatise on arthropod brains, Hans von Alten (1910) focuses on a specific functional group of insects-the flying Hymenoptera-which exhibit a spectrum of lifestyles ranging from solitary to social. His work presents a distinctive comparative neuro-anatomical approach rooted in an eco-evolutionary and eco-behavioral background. We regard his publication as an exceptionally valuable source of information and seek to inspire the research community dedicated to the study of the insect brain to explore its insights further, even after more than 110 years. We have translated and annotated his work, expecting it to engage researchers not just with its remarkable drawings but also with its substantive content and exemplary research strategy. The present text is designed to complement von Alten's publication, situating it within the temporal context of nineteenth-century and early twentieth-century studies, and to draw connections to contemporary perspectives, especially concerning a central brain structure: the mushroom body.

Ultra-Conserved Elements and morphology reciprocally illuminate conflicting phylogenetic hypotheses in Chalcididae (Hymenoptera, Chalcidoidea).

Recent technical advances combined with novel computational approaches have promised the acceleration of our understanding of the tree of life. However, when it comes to hyperdiverse and poorly known groups of invertebrates, studies are still scarce. As published phylogenies will be rarely challenged by future taxonomists, careful attention must be paid to potential analytical bias. We present the first molecular phylogenetic hypothesis for the family Chalcididae, a group of parasitoid wasps, with a representative sampling (144 ingroups and seven outgroups) that covers all described subfamilies and tribes, and 82% of the known genera. Analyses of 538 Ultra-Conserved Elements (UCEs) with supermatrix (RAxML and IQTREE) and gene tree reconciliation approaches (ASTRAL, ASTRID) resulted in highly supported topologies in overall agreement with morphology but reveal conflicting topologies for some of the deepest nodes. To resolve these conflicts, we explored the phylogenetic tree space with clustering and gene genealogy interrogation methods, analyzed marker and taxon properties that could bias inferences and performed a thorough morphological analysis (130 characters encoded for 40 taxa representative of the diversity). This joint analysis reveals that UCEs enable attainment of resolution between ancestry and convergent/divergent evolution when morphology is not informative enough, but also shows that a systematic exploration of bias with different analytical methods and a careful analysis of morphological features is required to prevent publication of artifactual results. We highlight a GC content bias for maximum-likelihood approaches, an artifactual mid-point rooting of the ASTRAL tree and a deleterious effect of high percentage of missing data (>85% missing UCEs) on gene tree reconciliation methods. Based on the results we propose a new classification of the family into eight subfamilies and ten tribes that lay the foundation for future studies on the evolutionary history of Chalcididae.

Courtship, Mating Behavior, and Ovary Histology of the Nymph Parasitoid Psyllaephagus bliteus (Hymenoptera: Encyrtidae).

The potential of the parasitoid Psyllaephagus bliteus Riek for the biological control of the eucalyptus pest Glycaspis brimblecombei Moore (Hemiptera: Aphalaridae) nymphs is high. This research sought to analyze the courtship, male competition, and mating behavior of P. bliteus at the proportions of 1:1 and 2:1 males to female in a Petri dish (5 cm diameter), and to describe the ovary histology of virgin and mated females of this parasitoid. At 1:1, males touch the antennae and thorax-abdomen of females during courtship, but females avoid mate attempts before they are 48 h old. At 2:1, the competition between male parasitoids inhibits mating. The histology of ovaries of virgin and mated P. bliteus females is similar, with two well-defined germarium and vitellarium regions, with oocytes at different developmental stages, including mature ones rich in yolk and with eggshell. A clearer understanding of the reproductive behavior and histology of P. bliteus aids in the use of this parasitoid for the biological control of G. brimblecombei.

Body and Wing Allometries Reveal Flight-Fecundity Tradeoff in Response to Larval Provisioning in Osmia lignaria (Hymenoptera: Megachilidae).

Variation in body size has important implications for physical performance and fitness. For insects, adult size and morphology are determined by larval growth and metamorphosis. Female blue orchard bees, Osmia lignaria, (Say) provision a finite quantity of food to their offspring. In this study, we asked how provision-dependent variation in size changes adult morphology. We performed a diet manipulation in which some larvae were starved in the final instar and some were given unlimited food. We examined the consequences on adult morphology in two ways. First, allometric relationships between major body regions (head, thorax, abdomen) and total body mass were measured to determine relative growth of these structures. Second, morphometrics that are critical for flight (wing area, wing loading, and extra flight power index) were quantified. Head and thorax mass had hyperallometric relationships with body size, indicating these parts become disproportionately large in adults when larvae are given copious provisions. However, abdominal mass and wing area increased hypoallometrically with body size. Thus, large adults had disproportionately lighter abdomens and smaller wing areas than smaller adults. Though both males and females followed these general patterns, allometric patterns were affected by sex. For flight metrics, small adults had reduced wing loading and an increased extra flight power index. These results suggest that diet quantity alters development in ways that affect the morphometric trait relationships in adult O. lignaria and may lead to functional differences in performance.

Multivariate ratio analysis and DNA markers reveal a new Australian species and three synonymies in eucalypt-gall-associated Megastigmus (Hymenoptera: Megastigmidae).

The genus Megastigmus Dalman, 1820 (Hymenoptera: Megastigmidae) contains potential biocontrol agents of the invasive eucalypt galling chalcid Leptocybe spp. (Hymenoptera: Eulophidae), with several species reported in various parts of the world. Species discrimination is challenging due to intraspecific morphological variation, difficulty in measuring sizes of body parts, and the lack of information regarding the global distribution of parasitic Megastigmus. We used two species commonly associated with Leptocybe in its native range to review taxonomic methods and determine the most reliable morphological characters in species delimitation. We examined size variation of body characters, and conducted species discrimination using multivariate ratio analysis, mitochondrial Cytochrome c oxidase subunit 1 (COI) and nuclear 28S rDNA (28S) sequences. Morphological traits were effective in species delimitation yet revealed high variation in several characters employed in current keys. Knowledge generated on morphology and DNA justified the description of a new species, M. manonae, sp. n., the first record of M. pretorianensis in Australia, and revised diagnostic characters for M. zvimendeli. Based on these diagnostic characters and molecular data, we synonymize three species (M. judikingae, syn. n., from Australia, M. sichuanensis, syn. n., from China and M. icipeensis, syn. n., from Kenya) with M. zvimendeli. Our findings highlight the importance of molecular markers in assisting taxonomic decision-making and the need for coordinated work in identifying Megastigmus associated with Leptocybe spp.

New records of nocturnal Anomaloninae (Hymenoptera: Ichneumonidae) in South America.

We report for the first time Aphanistes ruthae Alvarado, 2018 in Venezuela and Castrosion renei Gauld & Bradshaw, 1997 in South America (Venezuela and Brazil). Castrosion renei is associated with the amazon rainforest in the Amazonas and Maranhão, States of Brazil.

Dating Tips for Divergence-Time Estimation.

The molecular clock is the only viable means of establishing an accurate timescale for Life on Earth, but it remains reliant on a capricious fossil record for calibration. 'Tip-dating' promises a conceptual advance, integrating fossil species among their living relatives using molecular/morphological datasets and evolutionary models. Fossil species of known age establish calibration directly, and their phylogenetic uncertainty is accommodated through the co-estimation of time and topology. However, challenges remain, including a dearth of effective models of morphological evolution, rate correlation, the non-random nature of missing characters in fossil data, and, most importantly, accommodating uncertainty in fossil age. We show uncertainty in fossil-dating propagates to divergence-time estimates, yielding estimates that are older and less precise than those based on traditional node calibration. Ultimately, node and tip calibrations are not mutually incompatible and may be integrated to achieve more accurate and precise evolutionary timescales.

DNA barcoding the bees (Hymenoptera: Apoidea) of Chile: species discovery in a reasonably well known bee fauna with the description of a new species of Lonchopria (Colletidae).

We compare the diversity of bees in the Chilean fauna as understood from traditional taxonomy-based catalogues with that currently known from DNA barcodes using the BIN system informed by ongoing morphology-based taxonomic research. While DNA barcode surveys of the Chilean bee fauna remain incomplete, it is clear that new species can readily be distinguished using this method and that morphological differentiation of distinct barcode clusters is sometimes very easy. We assess the situation in two genera in some detail. In Lonchopria Vachal one "species" is readily separable into two BINs that are easily differentiated based upon male mandibular and genitalic morphology (characters generally used in this group) as well as female hair patterns. Consequently, we describe Lonchopria (Lonchopria) heberti Packer and Ruz, new species. For Liphanthus Reed, a large number of new species has been detected using DNA barcoding and considerable additional traditional morphological work will be required to describe them. When we add the number of BINs (whether identified to named species or not) to the number of Chilean bee species that we know have not been barcoded (both described and new species under study in our laboratories) we conclude that the bee fauna of Chile is substantially greater than the 436 species currently known. Spanish language abstract available as supplementary data 1 .

An Old Remedy for a New Problem? Identification of Ooencyrtus kuvanae (Hymenoptera: Encyrtidae), an Egg Parasitoid of Lycorma delicatula (Hemiptera: Fulgoridae) in North America.

Spotted Lanternfly, Lycorma delicatula (White) is a recently introduced pest of Tree-of-Heaven, Ailanthus altissima (Mill.) Swingle in North America. Natural enemy surveys for this pest in Pennsylvania in 2016 recovered an encyrtid egg parasitoid from both field collections and laboratory rearing of field-collected L. delicatula egg masses. Both molecular and morphological data confirm that the egg parasitoids are Ooencyrtus kuvanae (Howard) (Hymenoptera: Encyrtidae). Ooencyrtus kuvanae (Howard) is primarily an egg parasitoid of gypsy moth, Lymantria dispar (L.), and was introduced to North America in 1908 for gypsy moth biological control. Although O. kuvanae is known to attack multiple host species, to our knowledge, this is the first report of O. kuvanae as a primary parasitoid of a non-lepidopteran host. Potential of O. kuvanae in the biological control of L. delicatula in North America and research needs are discussed.

A new xyelotomid (Hymenoptera) from the Middle Jurassic of China displaying enigmatic venational asymmetry.

BACKGROUND: Pterygota insects typically have symmetric veins in left and right wings. For studying taxonomy and phylogeny of fossil insects, venational patterns are commonly used as diagnostic characters, in conjunction with preserved body characters. Some examples of asymmetrical venation are known among extant insects, but only a few fossil insects with asymmetric wings have been reported, among which a previously described xyelotomid of Hymenoptera, Xyelocerus diaphanous, displays an unusual, small cell of vein Rs in the left forewing, but not in the right. RESULTS: Herein we report a new sawfly of the family Xyelotomidae, Aethotoma aninomorpha gen. et sp. nov., from the late Middle Jurassic of China having a simple Sc in the forewing and Sc with two branches in the hind wing. In additional, the new specimen exhibits an enigmatic venational asymmetry. In the right forewing, crossvein 2r-rs of forms a loop, then forks into 2 long branches reaching Rs, while 2r-rs of the left forewing forks into 2 short branches reaching Rs, in contrast to a linear 2r-rs in typical fossil and extant sawflies. CONCLUSION: Such rare asymmetrical venation found from fossil sawflies provides a glance at early occurrences of venational variability and instability, or possibly aberrational development, for insects in the late Middle Jurassic.

Why many Batesian mimics are inaccurate: evidence from hoverfly colour patterns.

Mimicry is considered a classic example of the elaborate adaptations that natural selection can produce, yet often similarity between Batesian (harmless) mimics and their unpalatable models is far from perfect. Variation in mimetic accuracy is a puzzle, as natural selection should favour mimics that are hardest to distinguish from their models. Numerous hypotheses exist to explain the persistence of inaccurate mimics, but most have rarely or never been tested against empirical observations from wild populations. One reason for this is the difficulty in measuring pattern similarity, a key aspect of mimicry. Here, we use a recently developed method, based on the distance transform of binary images, to quantify pattern similarity both within and among species for a group of hoverflies and their hymenopteran models. This allowed us to test three key hypotheses regarding inaccurate mimicry. Firstly, we tested the prediction that selection should be more relaxed in less accurate mimics, but found that levels of phenotypic variation are similar across most hoverfly species. Secondly, we found no evidence that mimics have to compromise between accuracy to multiple model species. However, we did find that darker-coloured hoverflies are less accurate mimics, which could lead to a trade-off between mimicry and thermoregulation in temperate regions. Our results shed light on a classic problem concerning the limitations of natural selection.

A Nonstationary Markov Model Detects Directional Evolution in Hymenopteran Morphology.

Directional evolution has played an important role in shaping the morphological, ecological, and molecular diversity of life. However, standard substitution models assume stationarity of the evolutionary process over the time scale examined, thus impeding the study of directionality. Here we explore a simple, nonstationary model of evolution for discrete data, which assumes that the state frequencies at the root differ from the equilibrium frequencies of the homogeneous evolutionary process along the rest of the tree (i.e., the process is nonstationary, nonreversible, but homogeneous). Within this framework, we develop a Bayesian approach for testing directional versus stationary evolution using a reversible-jump algorithm. Simulations show that when only data from extant taxa are available, the success in inferring directionality is strongly dependent on the evolutionary rate, the shape of the tree, the relative branch lengths, and the number of taxa. Given suitable evolutionary rates (0.1-0.5 expected substitutions between root and tips), accounting for directionality improves tree inference and often allows correct rooting of the tree without the use of an outgroup. As an empirical test, we apply our method to study directional evolution in hymenopteran morphology. We focus on three character systems: wing veins, muscles, and sclerites. We find strong support for a trend toward loss of wing veins and muscles, while stationarity cannot be ruled out for sclerites. Adding fossil and time information in a total-evidence dating approach, we show that accounting for directionality results in more precise estimates not only of the ancestral state at the root of the tree, but also of the divergence times. Our model relaxes the assumption of stationarity and reversibility by adding a minimum of additional parameters, and is thus well suited to studying the nature of the evolutionary process in data sets of limited size, such as morphology and ecology.

Bristles reduce the force required to 'fling' wings apart in the smallest insects.

The smallest flying insects commonly possess wings with long bristles. Little quantitative information is available on the morphology of these bristles, and their functional importance remains a mystery. In this study, we (1) collected morphological data on the bristles of 23 species of Mymaridae by analyzing high-resolution photographs and (2) used the immersed boundary method to determine via numerical simulation whether bristled wings reduced the force required to fling the wings apart while still maintaining lift. The effects of Reynolds number, angle of attack, bristle spacing and wing-wing interactions were investigated. In the morphological study, we found that as the body length of Mymaridae decreases, the diameter and gap between bristles decreases and the percentage of the wing area covered by bristles increases. In the numerical study, we found that a bristled wing experiences less force than a solid wing. The decrease in force with increasing gap to diameter ratio is greater at higher angles of attack than at lower angles of attack, suggesting that bristled wings may act more like solid wings at lower angles of attack than they do at higher angles of attack. In wing-wing interactions, bristled wings significantly decrease the drag required to fling two wings apart compared with solid wings, especially at lower Reynolds numbers. These results support the idea that bristles may offer an aerodynamic benefit during clap and fling in tiny insects.

Evaluation of native plant flower characteristics for conservation biological control of Prays oleae.

Several studies have shown that manipulating flowering weeds within an agroecosystem can have an important role in pest control by natural enemies, by providing them nectar and pollen, which are significant sources of nutrition for adults. The aim of this study was to assess if the olive moth, Prays oleae (Bernard, 1788) (Lepidoptera: Praydidae), and five of its main natural enemies, the parasitoid species Chelonus elaeaphilus Silvestri (Hymenoptera: Braconidae), Apanteles xanthostigma (Haliday) (Hymenoptera: Braconidae), Ageniaspis fuscicollis (Dalman) (Hymenoptera: Encyrtidae) and Elasmus flabellatus (Fonscolombe) (Hymenoptera: Eulophidae), as well as the predator Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), can theoretically access the nectar from 21 flowering weeds that naturally occur in olive groves. Thus, the architecture of the flowers as well as the mouthpart structure and/or the head and thorax width of the pest and its enemies were analyzed. The results suggested that all beneficial insects were able to reach nectar of the plant species from Apiaceae family, i.e. Conopodium majus (Gouan) Loret, Daucus carota L. and Foeniculum vulgare Mill., as well as Asparagus acutifolius L., Echium plantagineum L., Capsella bursa-pastoris (L.) Medik., Raphanus raphanistrum L., Lonicera hispanica Boiss. et Reut., Silene gallica L., Spergula arvensis L., Hypericum perforatum L., Calamintha baetica Boiss. et Reut, Malva neglecta Wallr. and Linaria saxatilis (L.) Chaz. P. oleae was not able to access nectar from five plant species, namely: Andryala integrifolia L., Chondrilla juncea L., Dittrichia viscosa (L.) Greuter, Sonchus asper (L.) Hill and Lavandula stoechas L.

Antennal Sensilla and Sexual Dimorphism of the Parasitoid Trichospilus pupivorus (Hymenoptera: Eulophidae).

Sensory structures (sensilla) of insects are present in high number in the antennae are important for perceiving environmental cues. Thus, sensilla play an important role in the localization, discrimination, and acceptance of a possible host by parasitoid insects. The sensilla, classified according to their shape, size, and distribution, may also show sexual dimorphism in insects. The types and distribution of antennal sensilla in female and male parasitoid Trichospilus pupivorus (Ferriere, 1930) (Hymenoptera: Eulophidae) were evaluated. T. pupivorus females had longer antennae than males. Both males and females have ten sensilla types with higher abundance of placoid sensilla in females, which suggest a possible functional dimorphism.

New fossil ephialtitids elucidating the origin and transformation of the propodeal-metasomal articulation in Apocrita (Hymenoptera).

BACKGROUND: Apocrita has a special structure that its first abdominal segment has been incorporated into the thorax as the propodeum. The remaining abdomen, metasoma, is connected to this hybrid region via a narrow propodeal-metasomal articulation forming a "wasp waist", which serves an important function of providing maneuverability, flexibility and posture for oviposition. However, the origin and transformation of the propodeal-metasomal articulation are still vague. Ephialtitidae, as the basal group of Apocrita from the Early Jurassic to the Early Cretaceous, have shown various types of propodeal-metasomal articulations. RESULTS: This study describes and illustrates two new genera with three new species, Acephialtitia colossa gen. et sp. nov., Proephialtitia acanthi gen. et sp. nov. and P. tenuata sp. nov., collected respectively from the Early Cretaceous Yixian Formation at Liutiaogou and the Middle Jurassic Jiulongshan Formation at Daohugou, both in Inner Mongolia, China. These genera are assigned to the Ephialtitidae based on their complete wing venation, e.g. 2r-rs, 2r-m, 3r-m and 2 m-cu always present in the forewings and Rs, M and Cu in the hind wings. These new fossil ephialtitids have well-preserved propodeal-metasomal articulations indicating metasoma is broadly attached to propodeum. CONCLUSION: The broad articulation between the propodeum and metasoma in basal Ephialtitidae, likely passed on from a still more basal family Karatavitidae, suggests three separate pathways of the transformation of the "wasp waist" in three different derived lineages leading from Ephialtitidae to: (i) Kuafuidae and further to the remaining Apocrita, (ii) Stephanidae, and (iii) Evanioidea. In addition, the demise of ephialtitid wasps lagging behind the flourishing of angiosperms suggests that ephialtitid extinction might have been mainly driven by competition with numerous new taxa (eg. the abundant Cretaceous xylophilous Baissinae and Ichneumonoidea) appeared just before or/and soon after the J/K boundary.

Four new species of the genus Diolcogaster Ashmead, 1900 (Hymenoptera: Braconidae: Microgastrinae) from South East Asia with a key to the Indian species.

Four new species of the genus Diolcogaster Ashmead, 1900 (Hymenoptera: Braconidae: Microgastrinae) are described and illustrated: Diolcogaster andamanensis n. sp. from the Andaman Islands, and D. duocolor n. sp., D. longistria n. sp. and D. solitarium n. sp. from mainland India. The solitary larval parasitoid D. solitarium was reared from Gatesclarkeana sp. (Lepidoptera: Tortricidae). A new combination, Diolcogaster tomentosae (Wilkinson, 1930) n. comb., is proposed for the Indian species Protomicroplitis tomentosae (Wilkinson, 1930) along with its redescription and documentation of the gregarious cocoons associated with the pyralid (Epipaschiinae) host feeding on Terminalia cattappa L.

Taxonomic review of the genus Hypomicrogaster Ashmead (Hymenoptera: Braconidae: Microgastrinae), with descriptions of 40 new species.

A taxonomic review of the genus Hypomicrogaster Ashmead is presented with the redescription and redelimitation of the already named species Hypomicrogaster ecus Nixon, H. imitator (Ashmead), H. tydeus Nixon and H. zonaria (Say). The review also implies eleven new synonymies, and a new combination for the species H. areolaris (Blanchard). Also, the present revision identified 40 new Hypomicrogaster species: Hypomicrogaster aodous n. sp., H. aplebis n. sp., H. cernus n. sp., H. crocinus n. sp., H. daktulios n. sp., H. deltis n. sp., H. duo n. sp., H. epipagis n. sp., H. espera n. sp., H. evrys n. sp., H. guille n. sp., H. hektos n. sp., H. hupsos n. sp., H. ingensis n. sp., H. insolitus n. sp., H. inversalis n. sp., H. koinos n. sp., H. largus n. sp., H. laxus n. sp., H. linearis n. sp., H. lineatus n. sp., H. luisi n. sp., H. masoni n. sp., H. mesos n. sp., H. mikrosus n. sp., H. multus n. sp., H. pectinatus n. sp., H. plagios n. sp., H. pollex n. sp., H. rugosus n. sp., H. scindus n. sp., H. sicingens n. sp., H. sicpollex n. sp., H. sicscindus n. sp., H. siderion n. sp., H. spatulae n. sp., H. specialis n. sp., H. tantillus n. sp., H. tetra n. sp., H. zan n. sp. The Hypomicrogaster species are using as hosts 11 families of Lepidoptera, and 52 confirmed lepidopteran species feeding on 34 families of plants. Additionally, a fully illustrated key to all known described species of Hypomicrogaster is presented.

First record of Stephanidae (Hymenoptera, Stephanoidea) for the fauna of Egypt.

The family Stephanidae (Hymenoptera, Stephanoidea) is recorded for the first time for the Egyptian fauna, with one species, Foenatopus bisignatus Aguiar & Jennings, 2010. A single specimen was collected among Acacia raddiana trees infested with Agrilus roscidus Kiesenwetter (Coleoptera, Buprestidae), which represents a likely new host record.

A revision of the Indian species of Oligosita Walker (Hymenoptera: Trichogrammatidae).

The Indian species of the genus Oligosita Walker, 1851 (Hymenoptera: Trichogrammatidae) are revised. One new species, Oligosita aseta Begum & Anis, sp. nov., is described based on specimens collected from Kerala, India. A key to the 16 Indian species of the genus is also given.