The Central European fauna, in the last decades, has been undergoing a strong transformation due to four main factors: the retreat of living organisms that require cool and wet habitats, the proliferation of organisms that thrive in warm and dry conditions, the northward migration of Mediterranean organisms, and the gradual establishment of plants and animals with tropical origins. In this study, we detail the changes in the orders Diptera, Hymenoptera, and Lepidoptera and analyze the establishment of non native insects and the northward migration of Mediterranean insect species. The transformation towards a Mediterranean-type fauna is prominently indicated by the population in total abundance increase of xerothermic Aculeata, bee flies (Bombyliidae), and horse flies (Tabanidae). Additionally, groups that require cool and wet ecological conditions, particularly hoverflies (Syrphidae), but also sawflies (Tenthredinidae) and tachinid flies (Tachinidae), have shown a notable decline. In nocturnal moths, we observe a decrease in species richness in certain areas, as well as frequent outbreaks in populations of some less climate-sensitive species. Some species of butterflies are less sensitive to the current extent of climate change, exhibiting significant population in total abundance growth under protected conditions. However, most of the previously sporadic and rare butterfly species have proven to be climate-sensitive, unable to achieve significant population in abundance growth even under strict nature conservation. In recent decades, the influx from Mediterranean regions and the establishment of tropical non native insect species have turned at an exponential rate. We have reviewed the presence of alien insect species, recording 803 alien insect species in our region; 298 of them have arrived in the past quarter-century, with a significant proportion (54%) originating from tropical and Mediterranean regions.

Temporal changes in population densities and species richness of three main pollinator groups—moths and butterflies (Lepidoptera); bees, wasps and sawflies (Hymenoptera); and hoverflies, horseflies, tachinids and bee flies (Diptera)—were investigated in the Carpathian Basin. Maintaining pollinator diversity is a crucial factor for preserving our biodiversity and ecosystems; furthermore, several pollinator species have a strong economic role in maintaining crop and fruit cultures. Our conclusions are based on our three and four decades of faunistic surveys in various regions of the Carpathian Basin. Analyzing and comparing our data with the historical data of the last 50 years, we concluded that densities of some pollinators declined during the past decade and a half (Symphyta, hoverflies), although populations of several species of Mediterranean origin grew (Aculeata) and new species even migrated from the warmer regions. In numerous cases, this decrease was dramatic: more than 90% decline of certain butterfly species were detected. On the other hand, the composition of pollinator fauna significantly changed due to the disappearance of some mountainous or mesophile species. The main reason for the decrease in pollinator communities is due partly to climatic change and partly to anthropogenic factors. Different groups of pollinators react differently: some groups like Syrphidae, Tachinidae, most of the butterfly families and bumblebees suffered a strong decline in the last two decades; other warm-loving groups like most of Aculeata and horseflies and bee flies showed a significant increase in population densities. Our conclusion: in our region, the pollinator crisis is present but moderate; however, there is a clear sign of the gradual transition of our pollinator fauna towards the Mediterranean type.

Temporal changes of population densities and species richness of three main pollinator groups: moths and butterflies (Lepidoptera), bees, wasps and sawflies (Hymenoptera) and hoverflies, horse-flies, tachninids and bee flies (Diptera) were investigated in the Carpathian Basin. Maintaining pollinator divesrity is a crucial factor for preserving our biodiversity and ecosystems, furthermore several pollinator species has strong economic role in maintaning crop and fruit cultures. Our conclusions are based on our three or four decades of faunistic surveys in various regions of the Carpathian Basin. Analysing and comparing our data with the historical data of the last 50 years, we concluded, densities of some pollinators were declined during the past decade and the half (Symphyta, hoverflies), although populations of several species of Mediterranean-origin were grown (Aculeata) and even new species were migrated from the warmer regions. In numerous cases, this decrease was dramatic: more than 90% decrease of certain butterfly species were detected. On the other hand, the composition of pollinator fauna significantly changed due to the disappearance of some montaneous or mesophyle species. The main reason of decrease of pollinator communities is partly the climatic change and partly anthropogenic factors. Our conclusion: in our region, the pollinator crisis is present, but moderate; however, there is clear sign of the gradual transition of our pollinator fauna towards the Mediterranean type.

The Central European fauna, in the last decades, has been undergoing a strong transformation due to four main factors: the retreat of species that require cool and wet habitats, the proliferation of species that thrive in warm and dry conditions, the northward migration of Mediterranean species, and the gradual establishment of species with tropical origins. In this study, we detail the changes in the orders Hymenoptera, Diptera, and Lepidoptera, and analyze the establishment of non native insects and the northward migration of Mediterranean species. The transformation towards a Mediterranean-type fauna is prominently indicated by the population increase of xerothermic Aculeata, bee flies (Bombyliidae), and horse flies (Tabanidae). Additionally, groups that require cool and wet ecological conditions, particularly hoverflies (Syrphidae), but also sawflies (Tenthredinidae) and tachinid flies (Tachinidae), have shown notable decline. In nocturnal moths, we observe a decrease in species richness in certain areas, as well as frequent outbreaks in populations of some less climate-sensitive species. Some species of butterflies are less sensitive to the current extent of climate change, exhibiting significant population growth under protected conditions. However, most of the previously sporadic and rare butterfly species have proven to be climate-sensitive, unable to achieve significant population growth even under strict nature conservation. In recent decades, the influx from Mediterranean regions and the establishment of tropical non native insect species have turned into exponential rate. We have reviewed the presence of alien species, recording 803 alien insect species in our region, 298 of them have arrived in the past quarter-century, with a significant proportion (54%) originating from tropical and Mediterranean regions.