The Rhyacophila fasciata Species Complex (Trichoptera: Rhyacophilidae) in Central Europe with description of a new species, Rhyacophila loeffleri Valladolid & Waringer, n. sp., based on morphological, genetic and ecological evidence.

The morphology of the larva, pupa, male, and female of Rhyacophila loeffleri Valladolid & Waringer, n. sp., from Austria, Czech Republic, France, and Italy is described. Data from molecular analysis are also provided, based on mitochondrial cytochrome c oxidase subunit I (mtCOI), including sequences from German and Swiss specimens, and compared with those of samples of the nominate species R. fasciata Hagen 1859, as well as with other species and subspecies in the Rhyacophila fasciata Species Complex: R. septentrionis McLachlan 1865, R. denticulata McLachlan 1879, R. sociata Navs 1916, R. kykladica Malicky & Sipahiler 1993, R. delici Kuini & Valladolid 2020, R. fasciata viteceki Valladolid & Kuini 2020 and R. macedonica Karaouzas, Valladolid & Ibrahimi 2022. Our study revealed morphological differences between R. fasciata and R. loeffleri, as well as genetic differences among the other taxa of the R. fasciata Complex, supporting the recognition of R. loeffleri as a new species. Also, Rhyacophila fasciata viteceki is recognized as a distinct species, R. viteceki (status promotus), based on results of the molecular analysis.

Case design and flow resistance in high-alpine caddisfly larvae (Insecta, Trichoptera).

For evaluating hydraulic stress reduction strategies of caddisfly larvae, our study has three goals. First, creating a database on Reynolds numbers (Re) and drag coefficients valid for Limnephilidae larvae with cylindrical mineral cases. Second, evaluating the effects of submerged weight and biometry in cases with comparable length/width ratios. And third, collecting field data in an alpine environment for gaining insights into the hydraulic niches occupied by thirteen Drusinae species. Biometric data were subsequently combined with published Reynolds numbers and mean flow velocity data measured immediately upstream of Limnephilidae larvae at the moment of dislodgement. This provides drag coefficients for the range of Reynolds numbers obtained in the field. Data reveal that heavy cases strongly benefit from compensating drag by submerged weight, thereby enabling species to utilize high velocity spots, an important benefit for filtering species. Supplementary Information: The online version contains supplementary material available at 10.1007/s10750-022-04981-y.

Comparing head muscles among Drusinae clades (Insecta: Trichoptera) reveals high congruence despite strong contrasts in head shape.

The subfamily Drusinae (Limnephilidae, Trichoptera) comprises a range of species exhibiting differently shaped head capsules in their larval stages. These correspond to evolutionary lineages pursuing different larval feeding ecologies, each of which uses a different hydraulic niche: scraping grazers and omnivorous shredders sharing rounded head capsules and filtering carnivores with indented and corrugated head capsules. In this study, we assess whether changes in head capsule morphology are reflected by changes in internal anatomy of Drusinae heads. To this end, internal and external head morphology was visualized using µCT methods and histological sections in three Drusinae species-Drusus franzi, D. discolor and D. bosnicus-representing the three evolutionary lineages. Our results indicate that Drusinae head musculature is highly conserved across the evolutionary lineages with only minute changes between taxa. Conversely, the tentorium is reduced in D. discolor, the species with the most aberrant head capsule investigated here. Integrating previous research on Drusinae head anatomy, we propose a fundamental Drusinae blueprint comprising 29 cephalic muscles and discuss significance of larval head capsule corrugation in Trichoptera.

External and internal head anatomy of Drusus monticola (Trichoptera, Limnephilidae).

EXTERNAL AND INTERNAL HEAD ANATOMY OF DRUSUS MONTICOLA TRICHOPTERA LIMNEPHILIDAE: Caddisflies have evolved to a staggering diversity, and their larvae inhabit a wide range of different habitats. Also, the larvae differ in their (feeding) ecology, and hydrological niche preference. Consequently, groups differ in their external morphology, a fact that allows to identify many taxa to species-level in the larval stage. However, a comparative treatise on the internal anatomy of larval Trichoptera remains to be presented. Here, we provide a detailed study on the external and internal head anatomy of Drusus monticola, a member of the limnephilid subfamily Drusinae.We found 26 major muscles using µCT-scans, of which the muscles operating the mandibles were the largest. Overall, we could differentiate four main muscle groups: muscles operating the labrum, muscles operating the mandibles, muscles operating the maxillolabium and muscles operating the alimentary canal.The situation as observed in D. monticola is highly similar to that of D. trifidus, the only other Drusinae in which cephalic anatomy is known. We propose that the configuration (muscle origins and number) observed here is characteristic for an evolutionary lineage within Drusinae in which all known members share a scraping grazer feeding ecology. Other Drusinae, including such with modified head capsules, remain to be investigated. ZUSAMMENFASSUNG EXTERNE UND INTERNE ANATOMIE DES KOPFES VON DRUSUS MONTICOLA TRICHOPTERA LIMNEPHILIDAE: Köcherfliegen haben eine beeindru-ckende Diversität, und ihre Larven besiedeln ein breites Spektrum unterschiedlicher Habitate. Zudem unterscheiden sich diese Larven in ihrer (Ernährungs)-Ökologie und der Präferenz bestimmter hydrologischer Nischen. Folglich unterscheiden sich diese Gruppen in ihrer Morphologie, ein Umstand, durch den sie erst bestimmbar werden. Eine umfassende vergleichende Bearbeitung der internen Anatomie von Köcherfliegenlarven steht allerdings noch aus. Hier legen wir eine genaue Studie der Kopfkapselanatomie von Drusus monticola vor, einer Limnephilidae aus der Unterfamilie der Drusinae.Wir konnten mittels µCT-Scans 26 Muskeln feststellen, wobei die Mandibelmuskeln bei weitem die größten sind. Insgesamt konnten wir vier Muskelgruppen differenzie-ren: Muskeln des Labrums, Muskeln der Mandibeln, Muskeln des Maxillolabiums und Muskeln des Verdauungstrakts.Die Organisation, die bei D. monticola vorgefunden wurde, entspricht weitestgehend der, die anhand von D. trifidus beschrieben wurde - der einzigen anderen daraufhin erforschten Drusinae. Wir schließen daraus, dass die beobachtete Konfiguration für die evolutionäre Linie der schabenden Weidegänger innerhalb der Drusinae typisch ist. Bezüglich der Anatomie anderer Drusinae, insbesondere solcher mit abgewan-delten Kopfkapseln, sollten weitere Forschungen angestellt werden.

Identification and morphology of two polycentropodid caddisfly larvae from the Cevennes and the French and Italian Alps: Plectrocnemia cevennensis Coppa 2011 and Plectrocnemia praestans McLachlan 1884.

The collection of adults, mature male pupae, and the absence of confusing species at the sampling sites located in the Cevennes and French Alps enabled descriptions of the hitherto unknown larvae of Plectrocnemia cevennensis Coppa 2011 and P. praestans McLachlan 1884 (Trichoptera, Polycentropodidae). We present information on the morphology of the larvae and illustrate the most important diagnostic features. In the context of the larval key to European Plectrocnemia species by Waringer Graf (2020), P. cevennensis keys together with P. scruposa McLachlan 1880, whereas P. praestans keys with P. conspersa (Curtis 1834). These two species pairs are morphologically very close; P. cevennensis and P. scruposa can be separated by the numbers of secondary setae on the last abdominal sternum, but the separation of P. praestans and P. conspersa is not always possible.

The larva of Sericostoma galeatum Rambur 1842 (Trichoptera: Sericostomatidae), based on French material.

The present paper describes the previously unknown larva of Sericostoma galeatum based on French material. Information on the morphology of the larva is given, and the most important morphological characters are illustrated. Sericostoma galeatum is very close to the S. personatum / S. flavicorne species pair and cannot be separated yet from those confusing congeners. With respect to the distribution, S. galeatum is confined to the French, Italian, and Swiss western Alps and the Apennines. In addition, ecological information is provided.

Hydraulic niche utilization by larvae of the three Drusinae clades (Insecta: Trichoptera).

Hydraulic niche descriptors of final instar larvae of nine Drusus species (Trichoptera) were studied in small, spring-fed, first-order headwaters located in the Mühlviertel (Upper Austria), Koralpe (Carinthia, Austria), and in the Austrian and Italian Alps. The species investigated covered all three clades of Drusinae: the shredder clade (Drusus franzi, D. alpinus), the grazer clade (D. biguttatus, D. chauvinianus, D. dudor, D. monticola), and the filtering carnivore clade (D. chrysotus, D. katagelastos, D. muelleri). Flow velocity was measured at front center of 68 larvae, head upstream, on the top of mineral substrate particles at water depths of 10-30 mm, using a tripod-stabilized Micro propeller meter (propeller diameter = 10 mm). Each data series consisted of a sampled measurement lasting 30 s (measuring interval = 1 s). In total, 2040 single velocity measurements were taken. Instantaneous flow velocities and drag at the sites of the 68 larvae varied from 0 to 0.93 m s-1 and 0 to 8346 *10-6 N, respectively. Flow velocities and drag between the three clades were highly significantly different (p < 0.001); mean velocity (± 95% confidence limits) for the three clades were 0.09 ± 0.00 m s-1 for the shredder, 0.25 ± 0.00 m s-1 for the grazer, and 0.31 ± 0.01ms-1 for the filtering carnivore clade; the corresponding data for drag were (85 ± 18)*10-6 N, (422 ± 61)*10-6 N and (1125 ± 83)*10-6 N, respectively. Adhesive friction ranged from (41.07 ± 53.03)*10-6 N in D. franzi to (255.24 ± 216.87)*10-6 N in D. chrysotus. Except in D. franzi and D. dudor adhesive friction was always well below drag force, indicating that submerged weight alone was not sufficient to stabilize the larvae in their hydraulic environment. Reynolds numbers varied between 0 in D. franzi and D. alpinus, and 12,634 in D. katagelastos, with 7% of the total in the laminar (R < 500), 30%in the transitional (R = 500-2000), and 61%in the fully turbulent stage (R > 2000). Froude numbers (Fr) varied from 0 to 2.97. The two Drusus species of the shredder clade and three out of four species of the grazer clade were exposed to subcritical Fr < 1, one species of the grazer clade and two out of three species of the filtering clade to supercritical Froude numbers >1.

The larva of Rhyacophila albardana McLachlan 1879, including a discriminatory matrix to the Rhyacophila larvae with comb-shaped gills of Austria, Germany and Switzerland (Rhyacophilidae, Trichoptera).

Final instar larvae collected in the Rißbach (Isar catchment, Bavaria) were positively associated with adults of Rhyacophila albardana by barcoding; final instar larvae and adults of this species also were collected at the same time and site in the Lech River (Austria) in the absence of confusing species. These collections and associations enabled a description of the hitherto unknown larva of this species. We present information on the morphology of the larva and illustrate the most important diagnostic features. This dataset is included in a discriminatory matrix of the other larvae with comb-shaped gills (Rhyacophila Hyperrhyacophila Group) known so far from Austria, Germany, and Switzerland. Species can be separated by coloration patterns of the head and prosternum morphology. Rhyacophila albardana is known from Austria, France, Germany, Italy, and Switzerland (Neu et al. 2018).

Tools for instar determination of European caddisfly larvae (Insecta: Trichoptera).

The paper explores the adult-forewing-length to larval-head-width relationship as a basis for instar determination of final instar caddisfly larvae on a family level. In addition, reference data from published sources were used to extract series of percentage-head-width increments and factors-of-increase for penultimate to first instars. This material provides estimates for head widths of earlier instars on the family level.

The larva of Chaetopteryx rugulosa Kolenati 1848 (Trichoptera: Limnephilidae), with notes on ecology and zoogeography.

This paper gives a description of the hitherto unknown larva of Chaetopteryx rugulosa Kolenati 1848 (Trichoptera: Limnephilidae). Information on the morphology of the larva is given, and the most important diagnostic features are figured. In the context of the known European Chaetopterygini and Stenophylacini species, the larva of C. rugulosa can be separated from morphologically close species by metanotal sclerite morphology, setation, the extension of the lateral fringe, and by case morphology.

The larva of Plectrocnemia scruposa McLachlan 1880 (Trichoptera, Polycentropodidae.

This paper describes the previously unknown larva of Plectrocnemia scruposa McLachlan 1880. Information on the morphology of the 5th larval instar is given, and the most important diagnostic features are illustrated. In the context of existing identification keys, P. scruposa keys together with P. brevis McLachlan 1871, P. conspersa (Curtis 1834), and P. laetabilis McLachlan 1880. These species can be separated by the length of the outermost seta of the posterolateral trio on the last abdominal tergum and by presence/absence of a central pigmented mark on the posterior margin of the labrum. According to mandible morphology, the larva of this species appears to be mainly a predator and passive filter feeder of particulate organic matter.

The larva of Hydropsyche doehleri Tobias 1972, based on Swiss material (Hydropsychidae, Trichoptera).

This paper describes the previously unknown larva of Hydropsyche doehleri Tobias 1972. Species association was enabled by the fact that both larval and adult specimens were collected at the same location and that H. doehleri was the only Hydropsychidae collected at this site, based on light-trap samples of adults. In addition, association of larvae with adult males and females were performed using DNA sequence data from the mitochondrial cytochrome c oxidase region. Information on the morphology of the larva is given, and the most important diagnostic features separating H. doehleri from its sister taxon H. siltalai Döhler 1963 are discussed. In both species, gills are lacking on abdominal segment VII. In the context of the Hydropsychidae key of Waringer Graf (2011), the two species can be separated by the morphology and coloration of the frontoclypeal apotome, and by their distribution patterns: whereas H. siltalai is widespread in Europe, H. doehleri has been reported from only France, Italy, and southern Switzerland (Tessin).                #We dedicate this paper to Univ. Prof. Dr Hans Malicky on the occasion of his 85th birthday.

Hydraulic stress parameters of a cased caddis larva (Drusus biguttatus) using spatio-temporally filtered velocity measurements.

By studying hydraulic stress parameters of larvae of the cased caddisfly Drusus biguttatus (Pictet, 1834) in a tributary of the Schwarze Sulm (Carinthia, Austria), we aimed on (1) detecting the flow properties of the spatio-temporally filtered velocity measurements taken, and (2) on defining the hydraulic niche of this caddisfly larva. For this, we took 31 measurement series lasting 30 to 300 s, yielding 2176 single velocity measurements. The probability density functions of the 31 data series were Gaussian or sub-Gaussian, and the mean recurrent interval between velocity maxima within a data series was only 15.00 s. As a consequence, the Trichoptera larvae studied have to face strong flow accelerations in short intervals which is a much higher stress than conventional mean velocity measurements would suggest. The hydraulic niche of Drusus biguttatus is defined by instantaneous flow velocities ranging from 0.04 to 0.69 m s-1, by drag forces from 13 × 10-6 to 3737 × 10-6 N, by Froude numbers from 0.13 to 1.20, and mostly by Reynolds numbers > 2000. Under such conditions, only 5.1% of the drag force is compensated by submerged weight, whereas the remainder has to be counterbalanced by the active efforts of the larvae to remain attached to the substrate.

A new Drusinae species from the western Alps with comments on the subfamily and an updated key to filtering carnivore larvae of Drusinae species (Insecta: Trichoptera: Limnephilidae).

A new Drusinae species, Drusus katagelastos sp. nov., of the Drusus chapmani Species Complex, is described based on a male and associated larvae. Adult-larval association was achieved through DNA barcoding. The male of the new species differ from that of its congeners in the formation of the intermediate appendages and parameres. Information on the morphology of the larva is given, and important diagnostic features are discussed. In the context of filtering carnivore Drusinae, the larva of the new species can be separated from other filtering carnivore species by the dense cover of long translucent bristles within the frontal cavity surrounded by a circular corona of long bristles. Drusus katagelastos sp. nov. is known from only northwestern Italy (Piemonte).

The larva of Rhyacophila hartigi Malicky 1971, including a discriminatory matrix to the Italian Rhyacophila larvae with tufted multifilament gills (Rhyacophilidae, Trichoptera).

The collection of adults and larvae sampled at the same site on Sicily and the absence of confusing species at the sampling location enabled a description of the hitherto unknown larva of Rhyacophila hartigi Malicky 1971 (Trichoptera: Rhyacophilidae). We present information on the morphology of the larva and illustrate the most important diagnostic features. This dataset is included in a discriminatory matrix of the ten other Rhyacophila larvae with tufted multifilament gills of Italy described so far. Species can be separated by coloration patterns of head and pronotum, and by anal claw morphology; however, separation of the R. dorsalis-palmeni-simulatrix-vulgaris species quartet is not yet possible. Rhyacophila hartigi is restricted to the southern Apennine Peninsula and the island of Sicily (Cianficconi et al. 2008).

Discriminatory matrix for the larvae of the European Thremma species (Trichoptera: Thremmatidae).

This synoptic paper is intended to summarize and supplement the information available on the larvae of Thremma McLachlan 1876 in Europe. We present information on the morphology of the larvae and illustrate the most important diagnostic features. This information is used for the construction of a comprehensive discriminatory matrix for the four European species of family Thremmatidae Martynov 1935 known in the larval stage so far. In the context of this matrix, larvae can be easily diagnosed by the shape of mesonotal sclerites, foretrochantins, forefemora and ventral sclerites on abdominal segment I, by head coloration patterns, by case morphology, and by distribution. In addition, ecological characteristics and distributions of the European taxa are briefly discussed.

The larva of Drusus dudor Oláh, 2017, including an updated key to larval Drusinae Banks, 1916 (Insecta, Trichoptera, Limnephilidae).

The caddisfly Drusus dudor Oláh, 2017 (Limephilidae: Drusinae) was described from the Northwestern Italian Alps. We provide a detailed description of the larva, based on material from the Italian Province of Piemonte. Information on the morphology of the 5th larval instar is given, and the most important diagnostic features are illustrated. The larva is included in an updated key to larval Drusinae where D. dudor keys together with Drusus aprutiensis Moretti, 1981, D. camerinus Moretti, 1981, D. croaticus Marinkovic-Gospodnetic, 1971, D. mixtus (Pictet, 1834), and D. nigrescens Meyer-Duer, 1875. The species can be reliably separated by the morphology of the pronotum, the shape of the metanotal sclerites, and by morphological details of abdominal sternum I.

The larva of Plectrocnemia renetta Malicky 1975 (Trichoptera, Polycentropodidae), including a discriminatory matrix to the larvae of Plectrocnemia Stephens 1836 species of Greece.

This paper describes the previously unknown larva of Plectrocnemia renetta Malicky 1975. Information on the morphology of the final instar larva is given and the most important diagnostic features are illustrated. A preliminary discriminatory matrix for the Greek larvae of Plectrocnemia Stephens 1836 is also provided. Plectrocnemia renetta and P. conspersa conspersa (Curtis 1834) belong to the group where the inner and outer dorsal secondary setae on abdominal segment IX are strongly different in length. These two species can be separated from each other by the arrangement of muscle attachment spots on the head capsule, number and length of setae on abdominal sternum IX, and by distribution patterns. With respect to zoogeography, Plectrocnemia renetta has been reported from Cyprus, Turkey, and from the Greek islands of Ikaria and Samos.

Identification and morphology of a rhyacophilid caddisfly larva from Cyprus: Rhyacophila aphrodite Malicky 1975.

Rhyacophila aphrodite Malicky 1975 is a micro-endemic species of Cyprus and the only rhyacophilid caddisfly recorded on this island. This paper describes the previously unknown larva of this species. Information on the morphology of the final larval instar is given, and the most important diagnostic features are illustrated. In the context of existing Rhyacophilidae identification keys, the larva of R. aphrodite belongs to the group fitted with one single-filament gill on each side of the meso- and metathoraces and one four-filament gill on each side of abdominal segments I to VIII. In addition, a sword process is present on each anal proleg. The distal anal claw tooth is perpendicular to the longitudinal axis of the anal claw and shorter than half of the anal claw width at the distal tooth insertion.

The larvae of Limnephilus minos Malicky 1970 and Mesophylax impunctatus aduncus (Navás 1923) (Trichoptera: Limnephilidae), including a discriminatory matrix for the Greek limnephilid larvae with multifilament gills.

Limnephilus minos Malicky 1970 is a micro-endemic caddisfly restricted to the Greek island of Crete. Mesophylax impunctatus aduncus (Navás 1923) is known from Turkey and the southern Balkan peninsula; Greek records range from islands close to the mainland and Skiros to the northern mainland, and Attica. This paper describes the previously unknown larvae of both taxa. Information on the morphology of the 5th larval instar of each taxon is given, and the most important diagnostic characters are illustrated. A discriminatory matrix for the Greek limnephilid larvae with multifilament gills is also provided. In the context of existing identification keys, the larva of L. minos belongs to the group of Limnephilini larvae where face setae are lacking on the mid- and/or hind femora; the species keys together with L. auricula Curtis 1834 and can be separated from the latter species by setae present between the primary setae on the distal section of mid- and hind trochanters. In contrast, face setae are present on the mid- and/or hind femora in M. impunctatus aduncus. Its larva can be easily identified by the fact that 3 or more ventral-edge setae are present on the midfemur, by setae present on both sides of the anal slit, and by its grazer-type mandible lacking terminal teeth.