The continuing spread of the Asian tiger mosquito Aedes albopictus , a vector of many arboviruses and some dirofilarial worms, in Europe calls for advanced investigations on its ecological ability to establish and overwinter in temperate, more northern geographic regions. To meet this purpose, eggs of Ae . albopictus laboratory strains of tropical, subtropical and temperate origin were exposed to field conditions during one or two winter seasons in northeastern Germany. After 1 to 16 weeks of outdoor exposure, eggs were flooded in the laboratory, and the hatching rates were determined. During the winter season 2015/2016, when temperatures reached –10°C, the subtropical strain showed hatching after all time periods while the tropical strain displayed hatching only until two weeks of cold exposure. In the winter season 2016/2017, with temperatures as low as ‒6°C, all three strains produced hatching larvae after all time periods. Both the hatching rates and the hatching behaviour differed between the strains. Larvae of the subtropical and temperate strains hatched in installments over a period of four weeks while the larvae of the tropical strain hatched within a short time period, often one week. The results of the study demonstrate that Ae . albopictus strains of different, even tropical, origin might be able to survive a central European winter, although this is likely to depend on the specific course of the temperatures. Further studies with different temperature regimes and different mosquito strains are needed to specify these findings.

Background Aedes albopictus, a vector of numerous viruses and filarial worms, has already established in 20 countries in Europe, mainly colonising subtropical regions. Continuing adaptation to climatic conditions in temperate areas would probably result in a spread to more northern European countries, producing an increasing risk of mosquito-borne pathogen transmission over a much greater area. Based on previous studies showing that Ae. albopictus is able to overwinter in Germany, this study aims to determine more exactly its ecological limits of enduring low temperatures. Methods Non-diapausing and experimentally induced diapausing eggs of three different Ae. albopictus strains (tropical, subtropical and temperate origins) were exposed to four different regimes with constant temperatures and three different regimes with fluctuating temperatures in a course of a day for a minimum of 2 and a maximum of 30 days. The hatching rate of larvae after cold exposure of the eggs was taken as a measure of cold tolerance. Results The experiments showed that the tropical Ae. albopictus strain had a lower cold tolerance than the subtropical and the temperate strains. The eggs of all used strains were able to survive constant temperatures as low as −5 °C for an exposure period of 30 days, while constant temperatures as low as −10 °C were endured for 2 days by the tropical strain and for 10 and 20 days by the subtropical and temperate strains, respectively. At fluctuating temperatures, both the subtropical and the temperate strains exhibited hatching under all temperature regimes, even with a minimum temperature of −10 °C, whereas the tropical strain ceased hatching after an exposure period of 30 days under the temperature regime with a minimum temperature of −10 °C. The analyses showed that the temperature played the major role in interpreting the hatching rates of the eggs. The condition, whether the eggs were diapausing or not, had no significant influence, although results indicated a slightly higher cold tolerance of diapausing eggs at −10 °C. Conclusions It must be expected that subtropical and temperate strains of Ae. albopictus are able to withstand common central European winters and are able to establish in considerable parts of the continent.

Anopheles algeriensis, a thermophilic mosquito species widely distributed in the Mediterranean, is supposed to be extremely rare and to occur in very low abundances in central and northern Europe. Being one of seven native Anopheles species, it has been reported from Germany a few times only, with all but one report several decades ago. Only in 2013, the endemic persistence of the species was confirmed when two larval specimens were found north of Hamburg. We here report the trapping of An. algeriensis adults at three additional sites in northeastern Germany, with one of them representing two thirds of all mosquitoes collected over two monitored seasons, 2015 and 2017, and a second one with still 12.3% of all specimens caught during the mosquito season 2016. At a third site, one single female was trapped in 2015. Despite considerable efforts, breeding sites could not be identified at the two locations characterised by the high abundances. Anopheles algeriensis has been shown to be vector-competent for Plasmodium parasites and might locally play a role in malaria epidemiology when abundance is high.

Herein we describe nine species of Eocyzicus from Australia and re-describe the morphological variability of Eocyzicus parooensis Richter Timms, 2005 and Eocyzicus argillaquus Timms Richter, 2009. All species were previously delimited by molecular phylogenetic analyses and the species descriptions are based on the same individuals. Characters were scored with the aid of the taxonomic software DELTA. The morphological analyses largely corroborated the previously delimited species despite high levels of intraspecific variability that overlapped with interspecific variation in many instances. Morphological species delimitation was generally supported by principal component and canonical variate analyses. Characters best suited for morphological species identification were the numbers of growth lines on the carapace, the number of telsonic spines and the number of setae on the furca.

Uranotaenia unguiculata is a thermophilic mosquito species frequently occurring in the Mediterranean. Its first detection in the southern German Upper Rhine Valley in 1994 represented its northernmost distribution limit for a long time. During recent mosquito monitoring activities, two specimens of the species were trapped at different localities, about 70 km apart, in northeastern Germany, some 300-km latitude north of previous collection sites. It is not known whether Ur. unguiculata is vector-competent for disease agents although specimens collected in the field were found infected with West Nile virus and Dirofilaria repens. The finding of the species in northern Germany is probably a further example of mosquito species spreading northwards as a consequence of climate warming.