This is a large grey mosquito with white rings on the legs. The fertilized females spend the winter in suitable cool places, but if disturbed they may wake up and even start to suck blood. In fact this is the species that is nearly always responsible for mosquito bites in the middle of winter.
Gnats and mosquitoes
These are normally summer insects (see p. 47), but there are two species which are seen in winter, as they sometimes enter houses to spend the cold part of the year.