Although the newfound genus is extinct, bat flies still exist today, feeding exclusively on bats' blood. Some of the insects have even become specialized to live on specific bat species.

(Related: "Vampire Bats Have Vein Sensors.")

While there are hundreds of known bat fly species, most are poorly understood.

"First of all, it's hard to catch bats," Poinar said, "and [combing the bats for parasites is] like looking for fleas on mice. You don't see them."

Before Poinar discovered the amber containing the fossilized fly, nobody knew how recently the bugs had evolved to prey on bats alone. But even the 20-million-year-old fossil shows interesting bat-specific modifications, he said.

"The front legs are flattened, and they're held up between the head. These flattened legs