For decades, the story of the "tube mosquito" has circulated: a mosquito that appeared during World War II in the tunnels of the London Underground. People slept on platforms to shelter from air raids and were bitten. Scientists long assumed a new mosquito had adapted to life below ground within just a few generations. But that's not true. The new study shows that evolution works on a much longer timescale. The mosquito form Culex pipiens molestus thrives in warm, humid, often subterranean habitats in urban environments. It mates in confined spaces, remains active during winter, and bites humans. Females can produce their first batch of eggs without a blood meal, a rare ability called autogeny. But even though they are not forced to bite, they still do: they need blood to produce additional clutches, and the biting instinct remains. Its close relative, the above-ground form Cx. pipiens pipiens, prefers birds, requires open spaces for mating and enters winter dormancy. The two are morphologically indistinguishable. Genome data and historic specimens debunk the myth The research consortium led by Prof. Lindy McBride and Yuki Haba (Princeton University) sequenced the genomes of more than 800 mosquitoes from 44 countries, including historical specimens from London museums. Their extensive analysis shows: molestus did not arise in the underground, but aboveground in Mediterranean region. The researchers also found evidence that molestus adapted to human environments more than 1,000 years ago, long before modern cities emerged. "What I find most striking is that these mosquitoes began adapting to human environments thousands of years ago, above ground, in early settlements," says Dr Mine Altinli (BNITM), who contributed mosquito samples to the study along with Dr Tatiana Sulesco (BNITM). "Traits that likely emerged in response to those ancient settings now help them thrive in today's cities and underground spaces. Understanding this long-term relationship is essential for tackling the public health challenges they still pose." Implications for public health The study not only tells a surprising evolutionary story, it is also relevant to current public health. Cx. pipiens molestus is a potent vector for viruses such as West Nile virus. Knowing that this mosquito form is widespread and genetically diverse helps us better understand transmission routes, and offers clues about how disease vectors might behave in future urban settings.