UCL News


Press cutting: The germ that leaves butterflies all a-flutter

6 February 2007

Bacteria that specialise in killing only the male of the species have led to the creation of the demanding female that never has a headache.

Biologists studying the Hypolimnas bolina butterfly in the Pacific have found that its patterns of sexual behaviour are turned upside down by Wolbachia bacteria.

Males start turning down opportunities to procreate because they are too tired to go on while females become promiscuous sexual predators.

"Female promiscuity actually rises when male numbers are reduced," said Dr Sylvain Charlat [UCL Biology], who led the study published in the journal 'Current Biology'.

"Greater numbers of female partners leads to fatigue in males. They start producing smaller sperm packages. Unfortunately, the female butterflies instinctively know. This just makes them more rampant." …

Dr Greg Hurst [UCL Biology], one of the senior researchers, said that one of the key findings of the butterfly study was that while a huge proportion of the males could be wiped out by the bacteria the overall population of the colony remained viable.

"It's amazing that the numbers of male butterflies can get so low and yet the population is sustainable and stable," he said.

"You don't need many male butterflies to continue the population. This is partly because the decision to mate is mainly under female control. But the males have to work harder. We think the males must be able to get through 50 females - though they put less effort into each mating." …

Previous studies have suggested that understanding the role of Wolbachia in insects may lead to the possibility that malaria-carrying mosquitoes can be controlled effectively. …

Lewis Smith, 'The Times'