In the framework of the Mosquito Monitor project launched in 2019 by the ELKH Centre for Ecological Research (CER), researchers are asking the public to keep a close eye on invasive biting mosquitoes and report when they see any specimen of this species to www.szunyogmonitor.hu. The citizen science project, launched to assess the spread of invasive biting mosquito species in the country, which also spread pathogens and viruses that are dangerous to humans, will help the public assess the threats and support the development of appropriate protection strategies.
The three species studied – the Asian tiger mosquito, the Asian bush mosquito and the Korean mosquito – are opportunistic, actively biting humans, domestic and wild animals, amphibians, reptiles and birds. In this way, they can spread pathogens from animals to humans that are not carried by our native biting mosquito species. It is important to know, however, that the establishment of a dangerous invasive biting mosquito vector in Hungary requires a stable population of large numbers of the vectors, i.e. the invasive species. Therefore, one of the main objectives of the Mosquito Monitor project is to monitor the distribution of invasive species in the country.
Under this program, researchers are asking the public to send the mosquitoes they find to the Centre for Ecological Research site in Vácrátót, addressed to Dr Zoltán Soltész (Institute of Ecology and Botany, Centre for Ecological Research, 2163 Vácrátót, Alkotmány u. 2-4.), or send a photo of the insect to @email or use the MosquitoAlert mobile phone application for mosquito monitoring. The researchers will respond to emails and regular mail within a few days, and to data sent via the app a little later due to more complex validation, but in all cases they will send feedback on which species have been observed. If it happens not to be an invasive biting mosquito, they will explain in detail how the specimen submitted differs from the invasive ones.
In 2021, the researchers received 1,160 mosquitoes, of which 407 were found to be Asian tiger mosquitoes, 86 were Asian bush mosquitoes and 54 were Korean mosquitoes. The Asian tiger mosquito was mostly reported from Budapest and its surroundings, but was also sporadically present in the Transdanubian region. Most Asian bush mosquitoes were reported in and around Budapest, but the species was also found scattered across western Hungary and the north of the country. Most Korean mosquitoes were reported from Budapest and settlements northeast of the city, with scattered reports from the western part of the country.
How do biting mosquitoes overwinter?
This year's mild winter has favored biting mosquitoes, as colder weather means fewer overwintering individuals in spring. Biting mosquitoes have several strategies to get through this risky period: as adult imago, larvae or eggs. The earliest species to be seen are those that overwinter as imago, as some of the braver individuals may fly out of their hiding places – such as cellars, caves, sheds, mammal burrows – earlier on a sunny day, and as the weather warms up, more and more of these overwintered imago can be seen. However, the biting mosquito season really starts when warming of the weather is accompanied by rainfall. When this happens, rain or flooding rivers inundate the areas where the overwintering eggs are located. Thus, two factors are necessary for the development of biting mosquito larvae: suitable wetland habitat and higher temperatures. The warm April-May rains thus trigger an explosion in the development of biting mosquitoes. However, there was virtually no significant rainfall until the end of March this year.
Invasive species also overwinter as eggs. The females look for places that somewhat resemble a tree hole and where the water is not in contact with the soil. Examples include a rainwater barrel, a blocked gutter or discarded rubbish. If these laying sites dry out, the eggs have no problem and can even survive the winter in a more sheltered location. During spring rains, these cavities fill with rainwater and, if it is warm enough, the larvae hatch and start to develop.