Dale E. Greenwalt from the National Museum of Natural History in Washington D. C. and colleagues from the United Kingdom, and Sweden announced the discovery of the oldest known fossil mosquito that has blood in its stomach in the Oct. 14, 2013, edition of the journal Proceedings of the National Academy of Sciences.
The 46-million-year-old blood-engorged mosquito was discovered in shale in the Coal Creek Member of the Kishenehn Formation in northwestern Montana. The mosquito died soon after feeding and was encased in shale sediments after drowning. Thirty-six specimens of ancient mosquitoes were found at the site including 10 new mosquito species.
The blood-engorged mosquito was female. Male mosquitoes do not drink blood. Comparison of the female mosquito fossil to male mosquito fossils found at the same site through energy dispersive X-ray analysis revealed the same concentrations of carbon, oxygen, and other minerals in both the male and the female. The female abdomen contained nine times more iron than the male abdomen.
Further investigation of the iron structure indicated that the iron came from hemoglobin originally. The levels of iron in the female mosquito’s abdomen were found to be comparable to the levels of iron in human and animal blood. The iron source was identified as heme, the molecule that allows hemoglobin to transport oxygen. There was not sufficient genetic evidence in the fossil to determine what animal the blood came from
Blood containing fossil insects are exceedingly rare. Oxidation of blood components can eliminate the evidence of any blood consumption over time.
This fossil is the oldest know insect containing blood found to date.