A rare 46-million-year-old mosquito fossil containing dried animal blood in its belly has been discovered for the first time in a Montana riverbed in the US.
The insect's bloated abdomen carries traces of blood molecules dating back to 46 million years, researchers said.
Although scientists have found fossils of suspected blood-sucking insects, the creatures' feeding habits have mostly been inferred from their anatomy or the presence of blood-borne parasites in their guts.
A team led by Dale Greenwalt at the US National Museum of Natural History in Washington found that the fossilised mosquito contains molecules that provide strong evidence of blood-feeding among ancient the insects, 'nature.Com' reported.
"The abdomen of a blood-engorged mosquito is like a balloon ready to burst. It is very fragile. The chances that it wouldn't have disintegrated prior to fossilisation were infinitesimally small," said Greenwalt.
The insect was found not in amber, but in shale sediments from Montana. After 46 million years, any DNA would be long degraded, but other molecules can survive.
Researchers showed that the insect's abdomen still contains large traces of iron and the organic molecule porphyrin - both constituents of hemoglobin, the oxygen-carrying pigment found in vertebrate blood.
These molecules were either rare or absent in the abdomen of a fossilised male mosquito - which does not suck blood - of the same age, found at the same location.
The study was published in the journal Proceedings of the National Academy of Sciences.
