Solitary trap-nesting wasps are prospective bioindicators of anthropogenic pressures on natural ecosystems and one of the surrogate taxa for biodiversity assessments. The implementation of these studies is taxonomy-based and relies on accurate identification of species. The identification of larval stages of cavity-nesting Hymenoptera, collected using trap-nests, is complicated or impossible before the post-hibernation hatching of adults. DNA barcoding may allow the identification of the trap-nesting Hymenoptera species immediately after collection of the trap-nests, using larvae or dead specimens as sources of DNA. Using the standard barcoding sequence, we identified 33 wasp species from the families Vespidae, Pompilidae and Crabronidae, inhabiting trap-nests in Europe. Within-species and between-species genetic distances were estimated to evaluate the differences of intraspecific and interspecific genetic diversity. Genetic distances between related species indicated an obvious “barcoding gap”. Neighbour-joining analysis revealed that groups corresponding to taxa of genus level are cohesive as well. COI barcode approach was confirmed as a valuable tool for taxonomy-based biodiversity studies of the trap-nesting Hymenoptera.

A total of 693 small rodents were live-trapped in Lithuania and Norway. In Lithuania, the mice Apodemus flavicollis and A. agrarius were more frequently infested with ticks than the voles Microtus arvalis and Myodes glareolus. The overall prevalence of infestation with Ixodes ricinus in different sampling locations of Lithuania ranged for A. flavicollis from 0% to 92.3%, for M. glareolus from 5.9% to 100%, and for M. arvalis from 0% to 37.8%. In Norwegian sites the prevalence of infestation was higher for A. flavicollis (62.7–98% in different sites) than for A. sylvaticus (42.9–77.8%). The most intensive infestation of rodents with I. ricinus larvae was observed in May and June. Contrasting patterns of infestation with larvae and nymphs were observed in males and females of M. glareolus and A. flavicollis.

Phylogenetic relationships among Palaearctic Ribes and/or Onagraceae inhabiting Aphis species from five countries were examined using mitochondrial gene cytochrome oxidase I (CO-I) and nuclear gene elongation factor 1 α (EF-1α) sequences. There was no major conflict between the trees obtained from two data sets; nodes with strong bootstrap support from one analysis never contradicted those strongly supported by the other analysis. Palaearctic species of the subgenus Bursaphis (= "grossulariae" species group of the genus Aphis) form a monophyletic group within the genus Aphis. All these analyses indicated that Aphis grossulariae and A. schneideri are close relatives, which is supported by the information on experimental and probably also natural hybridisation. Our data indicate the independent colonisation of Ribes spp. by two species groups of the genus Aphis: A. triglochinis (subgenus Aphis s. str.), and A. grossulariae and A. schneideri (subgenus Bursaphis). Once the subgenus Bursaphis (and other subgenera) is accepted, the subgenus Aphis s. str. will require further subdivision.

Trypanosomatids from the Tabanidae family have not been studied in Lithuania in any detail. In this study, a nested PCR amplifying the DNA fragment coding the SSU rRNA was used to determine the Trypanosoma spp. prevalence and diversity in the Tabanidae family collected in Lithuania in 2018–2019. In total, 101 Tabanidae individuals were investigated from six areas in Lithuania, and 14 different species were identified. The overall positivity of Trypanosoma spp. DNA in tabanids was 50.5% (51/101). Tabanus maculicornis was the most abundant species and yielded the highest prevalence of trypanosomatids (84.62%, 22/26), while Hybomitra nitidifrons showed a high prevalence as well, reaching 77.8% (14/18). In flies of some species (Hybomitra lapponica and Hybomitra lurida), Trypanosoma was detected for the first time. Nine different haplotypes were detected as being distributed in different tabanid species. Analysis showed that most sequences obtained during our study were identical or extremely close to two major T. theileri subclades: TthI and TthII. Our data analysis suggests the presence of different Trypanosoma genotypes in the same tabanid species, meaning that different lineages of Trypanosoma could be more related to the vertebrate host and not the fly species. This is the first study of trypanosomatid parasites in tabanids from Lithuania, and our results are valuable in providing data on the diversity of these parasites in different Tabanidae species.