The rise and fall of a louse is tragic in the eyes of the louse and in the hearts of scientists who love that louse.

Until recently pubic lice, also known as "crabs", were riding high. Studies in the 60s, 70s and 80s reported more of them were taking up residence in their favourite neighbourhoods.

The louse had even overcome its poor reputation with scientists, who believed them to be lazy and slow. That characterisation was smashed to glorious pieces in 1983, thanks to a report by Ian Burgess and John Maunder, of the London School of Hygiene and Tropical Medicine, and Tin Than Myint, of the ministry of health in Rangoon, Burma.

Their study, Maintenance of the Crab Louse, Pthirus pubis, in the Laboratory and Behavioural Studies Using Volunteers, tells how they coated groups of pubic lice with powders that glow different colours under ultraviolet light. They then gave each group of lice a chance to migrate from its old home on one human body to a new home on another. The colours let the scientists see what moved where when - and it revealed a surprise.

Pubic lice showed themselves to be neither sedentary nor sluggish. Nay, says the report, "these observations suggest the converse is true and that these insects are extremely active".

But devastation visited the pubic louse community. A 2006 study called Did the Brazilian Kill the Pubic Louse?, written by NR Armstrong and JD Wilson, of Leeds General Infirmary, wonders at the sudden rarity of pubic lice in the UK and elsewhere. Published in the journal Sexually Transmitted Infections, the study suggests a possible cause:

"The drop in pubic lice in women appears to be most dramatic around 2000 and coincided with the introduction of extensive waxing techniques, such as the 'Brazilian', in women in the United Kingdom."

In this era where more and more animal species face the spectre of extinction, the "Brazilian" study sent alarm through the research community. Dutch naturalist Kees Moeliker, intrigued that the pubic louse might soon vanish altogether, started a campaign to collect and preserve some specimens for the Rotterdam Natural History Museum, of which he is a curator. "When the bamboo forests that the giant panda lives in were cut down, the bear became threatened with extinction," Moeliker explains. "Pubic lice can't live without pubic hair."

Moeliker is coming to Britain to collect some specimens. He will take part in the Ig Nobel Tour for National Science and Engineering Week (March 6-16). If you have a specimen of Phthiris pubis you'd like to donate to science, or know someone who has, please bring them to one of the events.

· Marc Abrahams is editor of the bimonthly Annals of Improbable Research and organiser of the Ig Nobel Prize. Details of this year's Ig Nobel Tour in the UK, which starts on March 6, are on http://improbable.com/improbable-research-shows/ig-uk-tour