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 + 0.01 m s−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.

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.

Insights can be gained by analysing the feeding decisions of animals in terms of nutrient demands at a species or community level. Using carbohydrate and protein food baits, resource use and food preferences of Formica (Serviformica) lemani were determined at nine locations situated at different altitudes (1875 to 2400 m a.s.l.) in the alpine grassland belt above the tree line in Austria and northern Italy. F. lemani is the most common species of ant in this habitat. Sucrose baits placed around ant colonies were visited by signifi cantly (3.9 times) more workers than protein baits. This indicates that sources of sugar (carbohydrate) are in short supply in the alpine zone, whereas availability of prey items appears to be less constraining. Overall, we recorded a decrease in the incidence of visits to baits from low (31.9% baits attracting ants at least once) to high altitudes (16.7%). Foraging ants never visited 51.5% of the baits exposed for periods of 75 min. This indicates that with increasing altitude competition for food among ant colonies becomes less intense in alpine grassland ant communities.

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 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.

Reliable biodiversity data are crucial for environmental research and management. Unfortunately, data paucity prevails for many regions and organismal groups such as aquatic invertebrates. High-throughput DNA-based identification, in particular DNA metabarcoding, has accelerated biodiversity data generation. However, in the process of metabarcoding, specimens are usually destroyed, precluding later specimen-based analyses. Metabarcoding of DNA released into the preservative ethanol has been proposed as a non-destructive alternative, but proof-of-principle studies have yielded ambiguous results, reporting variance in detection probability for various taxa and methodological biases. In this study, we tested the performance of preservative-based metabarcoding of aquatic invertebrates in comparison to a standard morpho-taxonomic assessment based on samples from one of Europe’s last free-flowing rivers, the Vjosa. Multi-habitat samples were collected at 43 sites in two seasons and stored in ethanol, after fixation in formaldehyde for morpho-taxonomic analyses. Preservative-based DNA metabarcoding detected three times more taxa but failed to detect other taxa found using the standard method. In addition to incomplete reference data and primer bias that likely precluded the detection of specific taxa, preservative-based DNA metabarcoding cannot provide accurate abundance estimates. However, the metabarcoding data revealed distinct small-scale and large-scale community patterns in the Vjosa river network, which were also recovered by quantitative data of the standard approach. Overall, our results indicate that preservative-based metabarcoding provides important biodiversity data, which could be further improved by quantitative validation. The method is robust and reliable, even though samples were taken under harsh field-conditions and stored without cooling. Further, our results emphasise the need for reliable DNA barcoding reference libraries. Building those may be supported by preservative-based metabarcoding that maintains intact vouchers for subsequent specimen-based analyses.

1. The mayfly Prosopistoma pennigerum (Müller, 1785) (Insecta: Ephemeroptera) once occurred in many European river networks. However, observations decreased in the last decades and the species can be considered largely extinct throughout Europe due to river alterations.2. Only three extant populations are known from Cabriel (southern Spain), Volga (Russia) and Vjosa (Albania) rivers.3. We recorded the species along a 150 km stretch in the Vjosa River in three sampling seasons (spring 2018, fall 2018 and fall 2019), counting up to 302 P. pennigerum per m 2 , the highest recorded abundance for the species to date. Moreover, we detected traces of environmental DNA in a newly designed targeted eDNA assay. 4. In our modelling approach we define the species' niche in a theoretically available niche space given by the Vjosa River network and predict a high probability of presence (θ) in downstream located sections of this river. Expected abundances (λ) could Gabriel Singer and Simon Vitecek shared senior authors.

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 differs 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).