We regard species, subspecies, and genera as measurable steps in an evolutionary process that requires time. Many species seem to require about one million years to become sufficiently distinct to be considered distinct. We test this in the damselfly genus Calopteryx Leach in Brewster, 1815, and especially in the group of Calopteryx splendens, trying to reconcile morphology with biogeography, including glaciations, and molecular phylogeny. We find that the C. splendens-group consists of four species, supported by distribution, morphology (wing patch size), COI, and ITS 1 and 2 (fragments of DNA), viz. C. exul Selys, 1853, C. samarcandica Bartenev, 1912, C. splendens (Harris, 1780), and C. xanthostoma (Charpentier, 1825). Only the first one fulfils the requirement of one million years in isolation, but all four seem to resist introgression. Despite enormous interpopulation variation, only two of the ca 25 named subspecies of C. splendens are considered valid: Calopteryx s. orientalis Selys, 1887, and C. s. syriaca Rambur, 1842. They began developing distinctive phenotypes during the Würm III deglaciation, ca 20 000 years ago, and have not yet reached species status. The taxonomic decisions made in this study include the placing of 17 named subspecies in synonymy with C. splendens splendens.

The last glacial maximum without doubt saw dramatic reductions in dragonfly populations that survived only in refugia. The Mediterranean basin was one of these, and central Asia another, more complex one. The western part of the basin, mainly Iberia, is home to C. xanthostoma, a species that recently became extinct in the Maghreb and is currently being outcompeted from south-western France to Liguria. There it meets C. splendens of various wing-patch morphs, coming from central Asia (Irano-Turania), via Anatolia, the Balkans, and Italy. To understand this, we assume two invasion waves occurred with different temperature preferences, causing them to disperse separately. The first one was cold-adapted, without a dark wing patch, and evolved in early preglacial times. It is still found along part of the southern margin of the Black Sea and probably evolved there. The second wave was warm-adapted with wide wing bands and androchrome females. It probably originated near the Zagros Mountains. All extant morphs can be explained as recent mixtures forming continuous clines of the two extremes.

Throughout the Holocene, the Zagros and the Black Sea populations recolonised central Asia and Siberia, eventually reuniting with those in the Baltic zone in the west, but this enormous territory needs much more study. In the south-east, Calopteryx did not cross the Pamir Mountain Knot. Calopteryx species that have been claimed to occur in the East Palaearctic mainly belong in Oriental genera such as Atrocalopteryx Dumont et al. 2005. The last common ancestor of American and Eurasian Calopteryx is believed to have lived in the Miocene age and migrated between continents via Beringia. It requires a genus name.

Measuring population trends of freshwater insects helps to assess their conservation status and to design management protocols for wetlands. Lestes macrostigma is restricted to temporary brackish waters, a limited and fragmented habitat. Throughout its range this species is threatened at different levels, and, in Bulgaria, it has been assessed as “Critically Endangered”. In the past, along the Black Sea coast, it was known to be abundant and reproducing at two sites: Shablenska Tuzla Lake and Poda Protected Area. At a third site, Pomorie Lake, only a few individuals were recorded without clear evidence of reproduction. We aimed at updating its distribution along the Bulgarian Black Sea coast and determining the conservation status of its populations by conducting surveys from 2021 to 2024 at 53 localities, mainly within coastal lagoons and estuaries. We recorded all Odonata species along with their various life stages and reproductive behaviour. Other resident species recorded in association with L. macrostigma were Lestes barbarus, L. dryas, Ischnura elegans, Aeshna affinis, Sympetrum fonscolombii, S. meridionale, and S. striolatum. We counted L. macrostigma adults along walks and extrapolated abundance over the entire sites and season. Lestes macrostigma population size reached hundreds of thousands of adults at Shablenska tuzla and Pomorie Lake. At Nanevska tuzla and Atanasovsko Lake, two new sites for the species, thousands of adults were present. However, we found that L. macrostigma had disappeared from at least a part of Poda Protected Area, most likely because of a change in water management practices. As the timing of the flooding period is a key feature of the species' habitat, we found that its presence in the temperate Bulgarian estuaries was unlikely. As conservation management plans are still lacking for Shablenska tuzla and Pomorie Lake, the future of the two largest L. macrostigma populations of Bulgaria of international importance seems tenuous and uncertain. Therefore, key actions for the conservation of L. macrostigma are the proper management of its existing reproductive sites and restoring or recreating temporary wetlands.

Variation in female coloration of Anax imperator has been described and interpreted in several different ways. In particular it has been widely believed that at least some younger green females change colour to blue with increasing age. In this study, the coloration of mature females was analysed using our own photographs from north-western Germany as well as many sourced from the internet. Our results clearly contradict previous explanations of colour change. The existence of different colour forms can be better explained by a model of sex-limited polychromatism. We identified two colour forms of mature females: blue and green. We also tentatively differentiated between two differing forms among the blue females: a deep blue form matching the colour of the males, and a pale blue form, both of which begin oviposition early in the season. The pale form was seen most frequently in our study region and also in photographs on the internet from other regions in Europe, Africa, and Central Asia. By rearing a female of the pale blue form, we followed the development of the juvenile coloration and observed its variability depending on temperature. In pale blue females, S2 was still green at the time of mating when they were still immature, and became blue by the time oviposition had commenced. Although a colour change did occur, it only related to one abdominal segment. Due to their rarity in our study area, little is known about the deep blue androchrome females and those with a predominantly green abdomen. We have never seen gynochrome females with a pure green abdomen, which are known mainly from England, demonstrating that significant regional differences occur in the frequency of green phenotypes. Regional compositions of phenotypes presumably have also changed with time; there are indications that blue or partly blue females have also recently become common in the British Isles. The vast majority of photographs of mating showed females that were not yet fully coloured, with the exception of one old female. We suppose that the vast majority of all mating takes place in the immature stage.

The accurate identification of species is critical for any biological study. Sometimes the morphological similarity between species in the same genus makes this difficult, as with the male larvae and exuviae of Anax imperator and A. parthenope, two dragonflies that often occur syntopically. This paper examines the utility of 13 numerical criteria (based on nine measurements of the mentum, anal pyramid and femur in the metathoracic legs) and one morphological criterion (shape of the margin of the epiproct expansion: straight or notched) to separate exuviae of both species. The shape of the margin of the epiproct expansion provided correct identification of 89 % of exuviae and the ratio between length and width of the epiproct expansion was the most reliable of the criteria used.

Indaeschna baluga was described by Needham & Gyger (1937) based on a male specimen collected from Mount Banahaw, Luzon, the Philippines. We show that the characters mentioned in the original description of I. baluga do not allow separation from the widespread Indaeschna grubaueri. However, the male superior appendages of the two species are morphologically distinct. Material of male I. grubaueri from Negros and Samar, Philippines, is found to belong to I. baluga. For Mindanao only females are available, which can at present not be identified to species level. Based on this, I. baluga is considered the only species of Indaeschna occurring in the Philippines (Luzon, Negros, and Samar), while its close relative I. grubaueri is restricted to Sundaland, distributed as far north as the Krah Isthmus.

Lestes yaojiae sp. nov., a new metallic green coloured Lestes species is described from high montane wetlands along the Yangzi River in Chongqing and Hubei provinces of China, based on both morphological and molecular evidence. The morphological differences between the new species and phylogenetically close species are discussed. The discovery of the new species facilitates the knowledge of the distributional pattern of the metallic green Lestes group in China.