Eocene and modern entomofauna differ-a Cretaceous-like larva in Rovno amber.

We report a 35 million-year-old lacewing larva from Ukrainian amber. This insect larva has a morphology up to now only known from 100 million-year-old amber. Therefore, this morphology survived more than 60 million years longer than previously assumed. Our find contradicts the common notion that the fauna 35 million years ago was already very modern.

Poxyaibamberus Andersen & Dantas, gen. nov. (Diptera, Chironomidae, Orthocladiinae) from Brazil.

Poxyaibamberus Andersen & Dantas, gen. nov. is erected based on the males of two species, P.jamanximensis Andersen & Dantas, sp. nov. from Jamanxim National Park, Pará State, Brazil, and P.ubajarensis Andersen & Dantas, sp. nov. from Ubajara National Park, Ceará State, Brazil. Both species have a comparatively short and wide head, with large eyes and short, five-segmented palps; a strong subapical seta on the ultimate flagellomere; scalpellate acrostichals; no setae on the wing veins except for one seta on the brachiolum; a long costal extension; and a large triangular anal point and a very long heel on the gonostylus. The systematic position of the new genus is briefly discussed.

Expanding the Mesozoic Record of Early Brachyceran Fly Larvae, including New Larval Forms with Chimera-Type Morphologies.

Diptera are one of the four megadiverse groups of holometabolan insects. Flies perform numerous ecological functions, especially in their larval stages. We can assume that this was already the case in the past; however, fly larvae remain rare in most deposits. Here we report new dipteran larvae preserved in Cretaceous (about 99 Ma) Kachin amber from Myanmar and, even older, Jurassic (about 165 Ma) compression fossils from China. Through light microscopy and micro-CT scanning we explore their peculiar morphology and discuss their possible phylogenetic affinities. Several larvae seem to represent the lineage of Stratiomyomorpha. A few others present characters unique to Xylophagidae (awl-flies), as well as to Athericidae (water sniper-flies), resulting in a chimeric morphology. Understanding the exact relationships of most of these specimens with a particular lineage remains challenging, since they differ considerably from any other known dipteran larvae and present some unique traits. Additionally, we report new specimens of Qiyia jurassica Chen et al., 2014, supposedly parasitic larvae, most likely representatives of Athericidae. These new findings offer valuable insights into the evolution of the early diversification of the brachyceran flies and underscore the importance of immature stages in understanding the evolutionary history and ecology of flies.

New records of immature aquatic Diptera from the Foulden Maar Fossil-Lagerstätte, New Zealand, and their biogeographic implications.

Background: The biogeographical and ecological history of true flies (Diptera) in New Zealand is little known due to a scarcity of fossil specimens. Here, we report a fauna of immature aquatic dipterans from freshwater diatomites of the early Miocene Foulden Maar Fossil-Lagerstätte in southern New Zealand. Methods: We document 30 specimens of immature dipterans, mostly pupae, and compare their external morphology to extant aquatic Diptera. Based on the reconstructed paleoenvironment of Foulden Maar, we discuss taxonomic, ecological and taphonomic implications of this early Miocene fauna. Results: Among Chironomidae, one pupal morphotype is attributed to Tanypodinae, one pupal morphotype and one larval morphotype are placed into Chironomus (Chironominae) and a further morphotype into Chironominae incertae sedis. Chaoboridae are represented by a pupal morphotype congeneric or very close to the extant Chaoborus, today globally distributed except for New Zealand. Additional immature specimens are likely larvae and puparia of brachyceran flies but cannot be identified to a narrower range. These finds document an aquatic dipteran fauna in New Zealand in the earliest Miocene and highlight Neogene extinction as a factor in shaping the extant Diptera fauna in New Zealand. Immature aquatic dipterans were a common and likely ecologically important component of the early Miocene Foulden Maar lake. Preservation of larvae and pupae may have been promoted by diatomaceous microbial mats and the light colour of the diatomite likely facilitated spotting of these minute fossils in the field.

Beneath the surface: Decoding the impact of Chironomus riparius bioturbation on microplastic dispersion in sedimentary matrix.

A detailed understanding of microplastics (MPs) behaviour in freshwater ecosystems is crucial for a proper ecological assessment. This includes the identification of significant transport pathways and net accumulation zones, considering their inherent, and already proven influence on aquatic ecosystems. Bioavailability of toxic agents is significantly influenced by macroinvertebrates' behaviour, such as bioturbation and burrowing, and their prior exposure history. This study investigates the effect of bioturbation activity of Chironomus riparius Meigen, 1804 on the vertical transfer of polyethylene MPs ex-situ. The experimental setup exposes larvae to a scenario of 10× the environmentally relevant high concentration of MPs (80 g m-2). Bioturbation activity was estimated using sediment profile imaging with luminophore tracers. This study demonstrated that spherical MPs are vertically transferred in the sediment due to the bioturbation activity of C. riparius larvae and that their presence influences the intensity of the bioturbation activity over time. The present findings provide a noteworthy contribution to the understanding of the relationship between ecosystem engineers and the dispersion and accumulation of MPs within freshwater ecosystems.

Scratching the tip of the iceberg: integrative taxonomy reveals 30 new species records of Microgastrinae (Braconidae) parasitoid wasps for Germany, including new Holarctic distributions.

Substantial parts of the European and German insect fauna still remain largely unexplored, the so-called "dark taxa". In particular, midges (Diptera) and parasitoid wasps (Hymenoptera) are abundant and species-rich throughout Europe, yet are often neglected in biodiversity research. One such dark taxon is Microgastrinae wasps (Hymenoptera: Braconidae), a group of parasitoids of lepidopteran caterpillars with 252 species reported in Germany so far. As part of the German Barcode of Life Project GBOL III: Dark Taxa, reverse DNA barcoding and integrative taxonomic approaches were used to shed some light on the German Fauna of Microgastrinae wasps. In our workflow, DNA barcoding was used for molecular clustering of our specimens in a first step, morphological examination of the voucher specimens in a second step, and host data compared in a third step. Here, 30 species are reported for the first time in Germany, adding more than 10% to the known German fauna. Information for four species is provided in a new Holarctic context, reporting them for the Nearctic or, respectively, Palaearctic region, and 26 additional country records are added from sequenced material available in the collections accessible to us. Molecular clusters that show signs of discrepancies are discussed. Results show that we are just scratching the tip of the iceberg of the unexplored Microgastrinae diversity in Germany.

Long-Term Chironomid Emergence at a Karst Tufa Barrier in Plitvice Lakes National Park, Croatia.

Chironomids are found in all types of freshwater habitats; they are a ubiquitous and highly diverse group of aquatic insects. Plitvice Lakes National Park is the oldest and largest national park in Croatia and consists of numerous and diverse freshwater habitats, making the area an ideal location for long-term research into the chironomid emergence patterns and phenology. The main objectives of this study were to identify the composition of the chironomid community, determine the phenology of the identified species, and assess the main factors influencing their emergence in Plitvice Lakes. During 14 years of research, more than 13,000 chironomids belonging to more than 80 species were recorded. The most abundant species was found to be Parametriocnemus stylatus. The highest abundance of chironomids was recorded in lotic habitats with faster water current over substrates of moss and algae and pebbles. Water temperature and the availability of organic matter were found to be the main factors that drive chironomid emergence at the tufa barrier studied. In the last years of this study, a prolonged flight period was observed. Although this is not statistically significant (at this stage of the study), it could be due to a higher water temperature in winter.

The Morphological Diversity of Dragon Lacewing Larvae (Nevrorthidae, Neuroptera) Changed More over Geological Time Scales Than Anticipated.

Nevrorthidae, the group of dragon lacewings, has often been considered a relic group. Today, dragon lacewings show a scattered distribution, with some species occurring in southern Europe, Japan, Australia, and one in China. The idea that this distribution is only a remnant of an originally larger distribution is further supported by fossils of the group preserved in ambers from the Baltic region (Eocene, ca. 35-40 MaBP) and Myanmar (Kachin amber, Cretaceous, ca. 100 MaBP). Larvae of the group are slender and elongated and live mostly in water. Yet, larvae are in fact very rare. So far, only slightly more than 30 larval specimens, counting all extant and fossil larvae, have been depicted in the literature. Here, we report numerous additional specimens, including extant larvae, but also fossil ones from Baltic and Kachin amber. Together with the already known ones, this sums up to over 100 specimens. We analysed quantitative aspects of the morphology of these larvae and compared them over time to identify changes in the diversity. Despite the enriched sample size, the data set is still unbalanced, with, for example, newly hatched larvae (several dozen specimens) only known from the Eocene. We expected little change in larval morphology over geological time, as indicated by earlier studies. However, on the contrary, we recognised morphologies present in fossils that are now extinct. This result is similar to those for other groups of lacewings which have a relic distribution today, as these have also suffered a loss in diversity in larval forms.

Facing the infinity: tackling large samples of challenging Chironomidae (Diptera) with an integrative approach.

Background: Integrative taxonomy is becoming ever more significant in biodiversity research as scientists are tackling increasingly taxonomically challenging groups. Implementing a combined approach not only guarantees more accurate species identification, but also helps overcome limitations that each method presents when applied on its own. In this study, we present one application of integrative taxonomy for the highly abundant and particularly diverse fly taxon Chironomidae (Diptera). Although non-biting midges are key organisms in merolimnic systems, they are often cast aside in ecological surveys because they are very challenging to identify and extremely abundant. Methods: Here, we demonstrate one way of applying integrative methods to tackle this highly diverse taxon. We present a three-level subsampling method to drastically reduce the workload of bulk sample processing, then apply morphological and molecular identification methods in parallel to evaluate species diversity and to examine inconsistencies across methods. Results: Our results suggest that using our subsampling approach, identifying less than 10% of a sample's contents can reliably detect >90% of its diversity. However, despite reducing the processing workload drastically, the performance of our taxonomist was affected by mistakes, caused by large amounts of material. We conducted misidentifications for 9% of vouchers, which may not have been recovered had we not applied a second identification method. On the other hand, we were able to provide species information in cases where molecular methods could not, which was the case for 14% of vouchers. Therefore, we conclude that when wanting to implement non-biting midges into ecological frameworks, it is imperative to use an integrative approach.

Extreme freshwater discharge events exacerbated by climate change influence the structure and functional response of the chironomid community in a biodiversity hotspot.

Global climate change is expected to exacerbate extreme discharge events in freshwater ecosystems as a consequence of changes in precipitation volume and snow cover duration. Chironomid midges were used as a model organism in this study because of their small size and short life cycles, which enable fast colonization of new habitats and great resilience. This resilience is often expressed in easy recolonization after an extreme event. Chironomid samples together with physico-chemical water measurements were collected for 14 years, between 2007 and 2020, in a karst tufa barrier that is part of the Plitvice Lakes National Park in Croatia. More than 13,000 individuals belonging to >90 taxa were collected. Mean annual water temperature increased by 0.1 °C during this period. Multiple change-point analysis revealed three main periods by discharge patterns: the first one from January 2007 to June 2010, the second from July 2010 to March 2013, characterised by extreme low discharge, and the third from April 2013 to December 2020, characterised by an increase in extreme peak discharge values. Based on multilevel pattern analysis, indicator species of the first and the third discharge period were detected. The ecological preferences of these species indicate an environmental change related to the changes in discharge. Along with species composition, functional composition has changed with the abundance of passive filtrators, shredders and predators increasing over time. Species richness and abundance did not change over the period of observation, thus emphasizing the importance of species-level identification in detecting the earliest community response to change that would otherwise be overlooked.

New species and records of Pseudochironomini Sæther, 1977 (Diptera, Chironomidae) from the Dominican Republic.

Background: Pseudochironomini is a relatively small and poorly-studied tribe of subfamily Chironominae (Diptera, Chironomidae). New information: Pseudochironomusruthae Andersen & Baranov sp. nov. is described and figured, based on a single male collected in a light trap at Matadero, Dominican Republic. The species can be separated from its congeners by the combination of the following characters: wing without dark bands, dorsocentrals in partly double row and apex of superior volsella rounded. The species is the first Pseudochironomus species to be formally recorded and described from the Caribbean. In addition, a new record of Manoapahayokeensis Jacobsen & Perry, 2002 from the Dominican Republic is given. One specimen was DNA-barcoded and the barcode is given.

The first fossil immature of Elmidae: an unusual riffle beetle larva preserved in Baltic amber.

Elmidae, riffle beetles, have both adult and immature stages that show specializations for water environments. Fossils of adults of Elmidae are already known from amber, however a record of immatures was so far lacking. We report here the first fossil larva of Elmidae, preserved in Baltic amber. To be able to access details of the body hidden by inclusions and "Verlumung" we conducted, in addition to optical documentation methods, micro-CT and synchrotron documentation methods. The larva is characterised by prominent dorso-lateral and lateral processes and a plate-like ventral operculum at the end of the abdomen. The new fossil has similarities in the general body shape and the prominent characters with some modern larvae of Elmidae. The posterior protrusions on the trunk end possibly represent gills, which would imply that fossil larvae of Elmidae also led a water-related life style similar to modern representatives.

Peering into the Darkness: DNA Barcoding Reveals Surprisingly High Diversity of Unknown Species of Diptera (Insecta) in Germany.

Determining the size of the German insect fauna requires better knowledge of several megadiverse families of Diptera and Hymenoptera that are taxonomically challenging. This study takes the first step in assessing these "dark taxa" families and provides species estimates for four challenging groups of Diptera (Cecidomyiidae, Chironomidae, Phoridae, and Sciaridae). These estimates are based on more than 48,000 DNA barcodes (COI) from Diptera collected by Malaise traps that were deployed in southern Germany. We assessed the fraction of German species belonging to 11 fly families with well-studied taxonomy in these samples. The resultant ratios were then used to estimate the species richness of the four "dark taxa" families (DT families hereafter). Our results suggest a surprisingly high proportion of undetected biodiversity in a supposedly well-investigated country: at least 1800-2200 species await discovery in Germany in these four families. As this estimate is based on collections from one region of Germany, the species count will likely increase with expanded geographic sampling.

A Lagerstätte from Australia provides insight into the nature of Miocene mesic ecosystems.

Reduced precipitation in the Miocene triggered the geographic contraction of rainforest ecosystems around the world. In Australia, this change was particularly pronounced; mesic rainforest ecosystems that once dominated the landscape transformed into the shrublands, grasslands, and deserts of today. A lack of well-preserved fossils has made it difficult to understand the nature of Australian ecosystems before the aridification. Here, we report on an exceptionally well-preserved rainforest biota from New South Wales, Australia. This Konservat-Lagerstätte hosts a rich diversity of microfossils, plants, insects, spiders, and vertebrate remains preserved in goethite. We document evidence for several species interactions including predation, parasitism, and pollination. The fossils are indicative of an oxbow lake in a mesic rainforest and suggest that rainforest distributions have shifted since the Miocene. The variety of fossils preserved, together with high fidelity of preservation, allows for unprecedented insights into the mesic ecosystems that dominated Australia during the Miocene.

New extreme morphologies as exemplified by 100 million-year-old lacewing larvae.

Larvae of the group Holometabola (beetles, wasps, flies, moths and others) differ significantly in their morphology from their corresponding adults. In most larvae, appendages and other structures protruding from the body (antennae, palps, legs, trunk processes) appear less elongate than in their corresponding adults, providing the impression that these larvae are restricted to a certain degree in developing more elongate structures. We provide here numerous counterexamples of larvae of lacewings (Neuroptera). These include different forms of elongated antennae, mandibles, maxillae, labial palps, legs, trunk processes and neck regions. Most of these examples are larvae preserved in different types of 100 million-year-old amber. The longest neck region was found in an extant specimen. All these examples demonstrate that certain branches of Neuroptera indeed had larval forms that possessed strongly elongated structures. Hence there is no principal constraint that hinders holometabolan larvae to develop such structures.

Global Size Pattern in a Group of Important Ecological Indicators (Diptera, Chironomidae) Is Driven by Latitudinal Temperature Gradients.

Size is one of the most outwardly obvious characteristics of animals, determined by multiple phylogenetic and environmental variables. Numerous hypotheses have been suggested to explain the relationship between the body size of animals and their geographic latitude. Bergmann's Rule, describing a positive relationship between the body size of endothermic animals and their geographic latitude, is especially well known. Whether or not insects exhibit a similar pattern has long been a subject for debate. We hypothesize that latitudinal size gradients are coupled to temperature variation affecting the metabolic rate of these merolimnic insects. We showcase a strong latitudinal size gradient in non-biting midges (Diptera: Chironomidae), based on the examination of 4309 specimens of these midges from around the world. Although phylogenetic position was a key predictor of wing length, we also found that wing length decreases by 32.4 µm per every 1 °C of mean annual temperature increase. This pattern was found across different taxa and could be detected in 20 of 24 genera studied. We discuss the reasons for this pattern origin and its palaeoecological implications.

Gathering at the top? Environmental controls of microplastic uptake and biomagnification in freshwater food webs.

Microplastics are ubiquitous in the environment, with high concentrations being detected now also in river corridors and sediments globally. Whilst there has been increasing field evidence of microplastics accumulation in the guts and tissues of freshwater and marine aquatic species, the uptake mechanisms of microplastics into freshwater food webs, and the physical and geological controls on pathway-specific exposures to microplastics, are not well understood. This knowledge gap is hampering the assessment of exposure risks, and potential ecotoxicological and public health impacts from microplastics. This review provides a comprehensive synthesis of key research challenges in analysing the environmental fate and transport of microplastics in freshwater ecosystems, including the identification of hydrological, sedimentological and particle property controls on microplastic accumulation in aquatic ecosystems. This mechanistic analysis outlines the dominant pathways for exposure to microplastics in freshwater ecosystems and identifies potentially critical uptake mechanisms and entry pathways for microplastics and associated contaminants into aquatic food webs as well as their risk to accumulate and biomagnify. We identify seven key research challenges that, if overcome, will permit the advancement beyond current conceptual limitations and provide the mechanistic process understanding required to assess microplastic exposure, uptake, hazard, and overall risk to aquatic systems and humans, and provide key insights into the priority impact pathways in freshwater ecosystems to support environmental management decision making.

Eco-morphological diversity of larvae of soldier flies and their closest relatives in deep time.

Stratiomyomorpha (soldier flies and allies) is an ingroup of Diptera, with a fossil record stretching back to the Early Cretaceous (the Barremian, about 125 MYA). Stratiomyomorpha includes at least 3,000 species in the modern fauna, with many species being crucial for ecosystem functions, especially as saprophages. Larvae of many stratiomyomorphans are especially important as scavengers and saproxyls in modern ecosystems. Yet, fossil larvae of the group are extremely scarce. Here we present 23 new records of fossil stratiomyomorphan larvae, representing six discrete morphotypes. Specimens originate from Cretaceous amber from Myanmar, Eocene Baltic amber, Miocene Dominican amber, and compression fossils from the Eocene of Messel (Germany) and the Miocene of Slovenia. We discuss the implications of these new records for our understanding of stratiomyomorphan ecomorphology in deep time as well as their palaeoecology.

An unusual 100-million-year old holometabolan larva with a piercing mouth cone.

Holometabola is a hyperdiverse group characterised by a strong morphological differentiation between early post-embryonic stages (= larvae) and adults. Adult forms of Holometabola, such as wasps, bees, beetles, butterflies, mosquitoes or flies, are strongly differentiated concerning their mouth parts. The larvae most often seem to retain rather plesiomorphic-appearing cutting-grinding mouth parts. Here we report a new unusual larva preserved in Burmese amber. Its mouth parts appear beak-like, forming a distinct piercing mouth cone. Such a morphology is extremely rare among larval forms, restricted to those of some beetles and lacewings. The mouth parts of the new fossil are forward oriented (prognathous). Additionally, the larva has distinct subdivisions of tergites and sternites into several sclerites. Also, the abdomen segments bear prominent protrusions. We discuss this unusual combination of characters in comparison to the many different types of holometabolan larvae. The here reported larva is a new addition to the 'unusual zoo' of the Cretaceous fauna including numerous, very unusual appearing forms that have gone extinct at the Cretaceous-Palaeogene boundary.

Checklist of aquatic Diptera (Insecta) of Plitvice Lakes National Park, Croatia, a UNESCO world heritage site.

Studies on aquatic Diptera in the Plitvice Lakes National Park (Croatia) conducted in the last 50 years have produced 157 species and 7 taxa of aquatic Diptera placed in 13 families. Samples were collected at 25 sampling sites representing the four main types of karst aquatic habitats: spring, stream, tufa barriers and lakes. All records of all the aquatic families of Diptera in Plitvice Lakes NP are summarized, including previously unpublished data. Twelve species new for Plitvice Lakes NP are recorded for the first time, belonging to the families: Chironomidae - Labrundinia longipalpis (Goetghebuer, 1921), Nilothauma brayi (Goetghebuer, 1921), Potthastia longimanus Kieffer, 1922, Polypedilum (Polypedilum) nubeculosum (Meigen, 1804), Tanytarsus brundini Lindeberg, 1963; Dixidae - Dixella autumnalis (Meigen, 1838); Scathophagidae - Acanthocnema latipennis Becker, 1894 and Stratiomyidae - Oxycera pardalina Meigen, 1822, Oxycera limbata Loew, 1862, Oxycera turcica Ustuner & Hasbenli, 2004, Nemotelus pantherinus (Linnaeus, 1758), Oplodontha viridula (Fabricius, 1775). The most species-rich family was the Chironomidae with 62 species (and an additional seven taxa), followed by the Empididae with 22 species and Limoniidae with 19 species. The highest number of species was recorded in springs. The relatively low number of species in certain families and the complete absence of some aquatic families shows that further research into the aquatic Diptera in Plitvice Lakes NP is needed.