Via The Verge:

according to new research, mosquitoes that feed on blood have been
around for at least 46 million years. Researchers led from
the Smithsonian’s National Museum of Natural History made the discovery
by studying fossilized mosquitoes. Eventually, they came across one that
appeared to still be filled with its final meal of blood — though that
may not sound like a rare phenomenon, it is. The researchers write that
such a finding has never been described before.