Lizzie Wade in Anthropocene:
During World War II, Londoners often sought shelter from German bombs in the city’s subway tunnels. There, they encountered another type of enemy: hordes of voracious mosquitoes. These weren’t your typical above-ground mosquitoes. They were natives of the Underground, born in pools of standing water that pockmarked the underground passageways. And unlike their open-air cousins, London’s subterranean skeeters seemed to love biting humans.
Fifty years after the war ended, scientists at the University of London decided to investigate the subway population. They collected eggs and larvae from subway tunnels and garden ponds and reared both populations in the lab. The outdoor mosquitoes fed on birds, but the tunnel bugs preferred mammal blood. And when the scientists put males and females from the different populations into close quarters designed to encourage mating, not a single pairing produced offspring. That sealed the deal: the underground mosquitoes were a whole new species, adapted to life in the subway tunnels people had built.
More here.