What Is The London Underground Mosquito?

By Owen Jones


Who would have thought that the London Underground is home to a unique species of mosquito? The species is called the London Underground mosquito and is considered to have evolved from Culex pipiens. The London Underground species has been dubbed Culex pipiens molestus, because it is a vigorous biter.

It is not new, but it is comparatively new in biological terms. Molestus is known to have bitten Londoners during the Second World War whilst they were taking refuge during the air raids. However, there are other references to a mosquito with the same name, molestus, 170 years before the war, when there was no underground railway system in London or anywhere else in the world.

This mosquito was first discovered in the London Underground, which is why it got its name, but it can be discovered in metro and underground railway stations all over the world. No one actually knows much about this insect species yet.

Some individuals suggest that it is a variant of a local Culex pipiens that has adapted to living in warmer, underground tunnels, while others say that is a southern (and therefore warmer) variant of C. pipiens that is able to live in the colder north because it has inhabited the warm train tunnels of the underground railways.

Yet others, notably Kate Byrne and Richard Nichols, suggest that it is a totally different species from Culex pipiens. Their proof for saying this is that there are differences between pipiens and molestus: they display very different behavioural patterns and do not mate readily with one other.

C. pipiens molestus will bite rats, mice and humans and dies in cold temperatures but remains active all year round, whereas C. pipiens can tolerate cold weather, only bites birds and hibernates if the weather gets very cold.

On the rare occasions when the two species cross breed, the eggs are infertile, which implies that they are distantly related if at all. Recent studies indicate that molestus originated in one source but spread rapidly throughout the world, perhaps in freight.

Second-hand tyres have been held responsible for spreading molestus around the world. There is a colossal international trade in second hand tyres and it is notoriously difficult to get all the water out of a tyre that has been left in the rain. Mosquitoes can breed in a minuscule amount of water, so this is a possibility.

There is a strange and not entirely explained twist to the story of the molestus, the American version of molestus pipiens still bites birds which leads some people to suggest that molestus is a separate species, but that it has become a hybrid in America with pipiens.

This is quite frightening, but quite possible, because the American pipiens can transmit human encephalitis brought about by the West Nile virus, an eruption of which hit New York in 1999.

There is much more to find out concerning the London Underground mosquito, since the story is only just beginning to unfold. The true story will probably come out of America where this new mosquito has proved to be the most dangerous.




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