Culex pipiens, or the northern house mosquito (NHM), is the most common mosquito species in urban and suburban areas of Massachusetts. This species is also the most dangerous mosquito species to humans in the state due to its habit of frequently invading homes year round, as well as its status as the primary vector of the West Nile virus and St. Louis Encephalitis. The NHM is also capable of transmitting eastern equine encephalitis and western equine encephalitis, and this species breeds in marshes and in standing water sources on residential lawns, making it the primary target of vector control operations in Massachusetts and other human-populated areas throughout the northern two thirds of the US. Unlike most mosquito species, the NHM is active year round due to its habit of overwintering within homes, garages, sheds and barns where it may become a nuisance on sunny and unseasonably warm winter days in Massachusetts.

Only fertilized NHM females overwinter within homes, and from spring until fall, they travel long distances in order to collect blood meals from humans during the first few hours following sunset. During the late summer and fall, NHMs cease feeding on blood in favor of nectar and other sugar-rich food sources in order to build up the body fat they need to survive indoors until the spring season. Before human dwellings were constructed, these mosquitoes overwintered within caves and tree hollows where they remained protected from the harsh winter climate. Today, NHMs prefer to overwinter within homes due to the greater number of available harborages where they remain hidden from humans. However, these mosquitoes can remain in heated homes throughout the winter and they often emerge from their harborages during sunny and warm winter days. Luckily, this species is not considered a disease threat within homes during the winter, but they usually pose a nuisance within the homes that they inhabit.

Have you ever encountered indoor mosquitoes during the winter?