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London underground source of new insect forms



London Times   August 26 1998
   
   
   A NEW species of mosquito is evolving on the London Underground in a
   development that has astonished scientists.
   
   The insects are believed to be the descendants of mosquitoes which
   colonised the tunnels a hundred years ago when the Tube was being dug.
   
   When they went below ground they were bird-biting pests. But over a
   century, deprived of their normal diet, the mosquitoes have evolved
   new feeding behaviour, dining on mammals including rats and mice - and
   human beings. They now plague maintenance workers.
   
   Kate Byne and Richard Nichols of Queen Mary and Westfield College in
   London have carried out tests to see if the Tube's mosquitoes, which
   have been named molestus, are now different from Culex pipiens, the
   bird-biting species which entered the Underground last century.
   
   To their amazement they found that it was almost impossible to mate
   those living above ground with those in the subterranean world,
   indicating that the genetic differences are now so great that the ones
   underground are well on their way to becoming a separate species.
   
   This usually happens only when species are isolated for thousands
   rather than tens of years.
   
   The team, whose findings are reported in BBC Wildlife magazine today,
   have also found genetic differences between mosquitoes on different
   Tube lines. They believe this is due to the draughts dispersing the
   insects along but not between lines.
   
   During the Second World War the insects attacked Londoners sheltering
   from Hitler's bombs.
   
   Roz Kidman Cox, the magazine editor, said: "It's a remarkable story of
   evolution. The scientists say that the differences between the above
   and below-ground forms are as great as if the species had been
   separated for thousands of years."
   
   The conditions on the Underground are probably ideal for mosquitoes to
   breed rapidly and frequently throughout the year. Temperatures can be
   balmy and the network is prone to penetration by water creating pools
   of stagnant water for breeding.
   
   There are more than 1,600 varieties of mosquitoes which live from the
   Arctic tundra to the tropical rain forests.
   
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