New records of Protonemura species are enumerated on the basis of specimens collected between 2015 and 2019 in the Greater and Lesser Caucasus. Three new species are proposed on the basis of males, females and nymphs: P. apetor sp. n. from Georgia, P. boris sp. n. from Azerbaijan and Georgia, and P. soad sp. n. from Armenia and Georgia. Comments are given on the variability of the adults of P. spinulata Martynov, 1928 and P. viridis Balinsky, 1950 on the basis of Azerbaijani and Georgian specimens. The hitherto unknown nymph of P. aculeata Theischinger, 1976, P. bacurianica bacurianica Zhiltzova, 1957, P. oreas Martynov, 1928, P. spinulata and P. viridis are described on the basis of association by pharate adults. Protonemura spinulata is new for Armenia, P. triangulata Martynov, 1928 is new for the Lesser Caucasus, and Nemoura dromokeryx Theischinger, 1976 is new for Georgia and the Caucasus. A checklist of the Protonemura species known from Anatolia, the Caucasus, the Alborz and the Levant is presented.

Known Plecoptera data published from Azerbaijan are critically reviewed. New records of 28 species are enumerated on the basis of specimens collected between 2017 and 2019, among them 16 are new for the fauna of Azerbaijan. Nemoura irani Aubert, 1964 is new for the whole Caucasian region, Leuctra sanainica Zhiltzova, 1960 and Plesioperla sakartvella (Zhiltzova, 1956) are new for the Greater Caucasus. The female and larva of an unknown Protonemura Kempny, 1898 species, collected in the Talysh Mts, are illustrated and described under temporary name Protonemura sp. AZE-1. A new species of Protonemura, collected both in the Azerbaijan and Georgian areas of the Greater Caucasus, will be formally described in a further paper. A male Protonemura specimen was found to be infected by mermithid worms, morphological lesions are illustrated and commented; this is the second documented case of mermithid infection in stoneflies. Subspecies level identity of Azerbaijani populations of Leuctra fusca (Linnaeus, 1758) proved to be problematic, morphological characters of the specimens are illustrated. Synonymy of Isoperla caucasica Balinsky, 1950 and I. pulchra Balinsky, 1950 under I. bithynica (Kempny, 1908) is disputed, the two names are combined under I. grammatica (Poda, 1761) sensu lato.

Throughout the ages, geological bedrock has significantly determined the structure of the Tatra stonefly taxocoenoses. Because of the high altitude and discharge of the streams, stoneflies are mainly affected by alkalinity, Ca, and Si. Statistical analysis has previously shown that alkalinity, Ca and Si content, catchment area, and altitude are correlated with the stonefly Tatrataxocenoses. In the present study, we recorded two different stonefly taxocenoses attached to different types of bedrock. For example, the stonefly species Amphinemura sulcicollis (Stephens, 1835), Protonemura auberti Illies, 1954, Protonemura nitida (Pictet, 1835), Leuctra braueri Kempny, 1898, and Dinocras cephalotes (Curtis, 1827) are characteristic for limestone brooks, while the genera Brachyptera Newport, 1848, Rhabdiopteryx Klapálek, 1902, Capnia Pictet, 1841, Perlodes Banks, 1903, Leuctra nigra (Olivier, 1811), and Perla grandis Rambur, 1842 are characteristic for crystalline streams. Furthermore, the Amphinemura sulcicollis species is characteristic of carbonate streams of the Carpathian Mts., while Brachyptera seticornis (Klapálek, 1902) is typical of crystalline streams. In crystalline streams, Perloidae represent 24–25%, however, just 13–15% in carbonate streams. Taeniopterygidae represent 11–14% in crystalline streams, while only 1–4% in carbonate streams. Finally, we recorded Nemouridae and Leuctridae as the dominate species in carbonate streams.

A new micropterous species, Leuctra khachapuri Žiak et Martynov, sp. nov., from the hippopus species-group is described and illustrated based on morphological features of males and females. The new species occurs in crenal waterbodies of the alpine zone of the Adjaro-Imeretian (Meskhetian) Mountain Range, the Lesser Caucasus.

Stonefly samples were collected from disturbed and undisturbed regions of two river basins, tributaries of the Upper Vah River basin (the West Carpathians). Water temperature, oxygen content, coarse benthic matter and some stonefly metrics (abundance, biomass, richness, index of diversity, % predators, % shredders, stonefly total score and stonefly average score) were all negatively influenced by the extent of urban and field land cover. Rivers with a high proportion of human land-use activities were positively correlated with fine benthic organic matter and the share of collector-gatherers and saprobic indices (organic pollution), as well as with a higher trophic status of streams. Taxa of different species groups or genera have different demands for microhabitats. The cumulative curve of stonefly distribution in microhabitats of the river bed has, in the L'ubochnianka River, an exponential form (reflecting an increase in stonefly density on coarse substrata and moss). In the human-influenced Revuca River, the curve's form is logarithmic, representing a reverse trend.