More and more often we find mosquitoes in our homes even in the middle of autumn or winter: this is due toincrease in average temperatures due to global warming, especially in “heat islands” of cities, and tonight lighting. The mild temperatures and the abundance of hours of light “deceive” these insects by moving the moment in which they enter their breeding phase further and further forward. winter quiescence said diapause.
The change in the life cycles of mosquitoes also has potential repercussions on public healthbecause it allows for greater permanence of infected mosquitoes, possible vectors of viral diseases such as Dengue Fever, Zika virus infection or West Nile Fever,
The life cycle of mosquitoes and when they are active
Mosquitoes are active at high temperatures, therefore mainly in summer, and then go through a period of winter quiescence (diapause) influenced both by the drop in temperatures and by the duration of daylight hours (photoperiod). When temperatures drop and the days “get shorter” in autumn, the common mosquito (Culex pipiens) goes into diapause in the adult phase, seeking shelter in cracks and ravines. The tiger mosquito (Aedes albopictus) instead overcomes the cold period at the stage of egg: the female, not being able to resist winter temperatures, ensures the survival of the species by laying thousands of eggs in sheltered places which will hatch when the heat arrives.
Because mosquitoes are also active in winter and in the cold months: the factors that modify their life cycle
In our latitudes, diapause in the common mosquito is stimulated by a day length of less than 12 hours and an average temperature of less than 18 °C. Currently, however, these insects are modifying their life cycle by shortening diapause in response to three factors: the mild and prolonged autumn climatethe “heat islands” of cities andlight pollution. In fact, artificial light at night can interrupt the diapause of mosquitoes, helping to prolong the survival of specimens in urban environments, compared to natural rhythms.
Furthermore, laboratory simulations have shown that the exposure of specimens of Culex at high temperatures that mimic the “heat island” effect induced it ovarian development and the blood feeding of females even in winter. Other studies conducted in the USA have found that short periods of increase in autumn temperatures in our latitudes keep females from Culex fertile and induce them to take another blood meal at the end of autumn.
It is also evident that the populations of tiger mosquito they are evolving and adapting to new environments: the adult females are acclimatizing to the cold and the diapausing eggs resist rather harsh winter temperatures allowing the geographical expansion of these insects further north. This is confirmed by a study published in 2024 by a group of researchers from the University of Thessaly and the University of Attica in Greece, which showed that warm winters prolong the active phase of many mosquito species, in particular Culex pipiens (the common mosquito) e Aedes albopictus (the tiger mosquito).
The survival of mosquitoes in winter is also a public health concern
The alteration of seasonal temperatures favors not only the survival of exotic species that accidentally arrived in Europe, but also the spread of viral diseases which in the past were present only in tropical and subtropical countries. Mosquitoes like that Culex are in fact vectors of the West Nile Fever virus and the tiger mosquito (Aedes albopictus), currently widespread in much of Italy, in areas of France and Spain and in other locations in the Mediterranean, is a vector of the Dengue, Chikungunya, Zika and Yellow Fever viruses.
In tropical environments, tiger mosquito populations are active all year round without going into diapause, but currently even in our latitudes the persistence of the activity throughout December and the delay in diapause means that infected mosquitoes carry viruses even in autumn and winter promote winter survival.
Understanding mosquito adaptation mechanisms is critical to developing effective prevention strategies of the diseases they can carry. For this reason, since 2014 “Mosquito Alert”, a project by, has been active in many European countries citizen science coordinated by several research centers with the aim of monitoring the spread of invasive mosquitoes, possible vectors of Zika, Dengue and West Nile Fever.
