London Underground mosquito

The London Underground mosquito, Culex pipiens f. molestus, is a form of mosquito. It is named for its biting of people sleeping in the London Underground railway system during the Blitz, but it has a worldwide distribution and long predates the existence of the London Underground. It was first described in the 18th century based on Egyptian specimens by the biologist Peter Forsskål (1732–1763). He named it Culex molestus due to its voracious biting, but later biologists reclassified it as Culex pipiens f. molestus because there were no morphological differences between it and Culex pipiens.

A study from 2004 analyzing DNA microsatellites suggested that it might be a distinct species, but a paper from 2012 reported it to be "a physiological and ecological variant of Cx. pipiens" which should not be considered a distinct species. As of 2024, the consensus among researchers is that it is not a distinct species, but a form of Culex pipiens, which is often referred to as Culex pipiens f. molestus.

It was widely believed that molestus originated in the London Underground less than 100 years ago, representing one of the most rapid events of adaptation and speciation. However, recent meta-analysis and large-scale genomic study have found that molestus instead evolved above ground in the Middle East ~2000 years ago, likely adapting to ancient human agricultural societies. molestus then colonized below ground habitats like subways and basements in northern Europe (and subsequently across the globe) as humans have developed modern cities more recently. The adaptive traits that evolved in the ancient times have become useful for them to colonize more recent urban environments, providing a striking example of 'exaptation'.