Scientists who study why species vanish are increasingly looking for ancient DNA. They find it easily enough in the movies; remember the mosquito blood in Jurassic Park that contained dinosaur DNA from the bug's last bite? But in real life, scientists haven't turned up multi-million-year-old DNA in any useable form.

Fortunately, a team at the Smithsonian Institution has now found something unique in a 46-million-year-old, fossilized mosquito — not DNA, but the chemical remains of the insect's last bloody meal.

California scientists are reporting a pair of victories in the epic struggle between man and mosquito.

A team at the University of California, Riverside, appears to have finally figured out how bugs detect the insect repellent known as DEET. And the team used its discovery to identify several chemical compounds that promise to be safer and cheaper than DEET, according to the report in the journal Nature.