Big-headed fossil flies track major ecological revolution

According to their research, published recently by The Canadian Entomologist, these fossils show their early evolution parallels an ecological revolution, one that formed the character of our modern natural communities.

The three new species of fossil big-headed flies are members of the living family Pipunculidae. One fossil, Metanephrocerus belgardeae, is well-enough preserved to name as a new species. It is named in honor of its finder, Azure Rain Belgarde, a student at the Paschal Sherman Indian School, who uncovered it on a field trip to the fossil deposits at Republic, Washington state.

The other two unnamed, more enigmatic species are described from less complete fossils uncovered at Quilchena in southern British Columbia.

"Big-headed flies are a group of bizarre insects whose round heads are almost entirely covered by their bulging compound eyes, which they use to hunt for mainly leafhoppers and planthoppers, renowned common garden insect pests," says Archibald.

"The newly discovered species were preserved in Eocene epoch fossil beds that are 49 million to 52 million years old, which is about 12 million to 15 million years after the extinction of the dinosaurs. This great extinction event also disrupted forests in which the dinosaurs had lived, with mostly low diversity and greatly disrupted food webs for millions of years."

By the time of these flies in the Eocene, however, forests had diversified again, but this time with many new kinds of flowering plants that are familiar to us today, such as birches, maples, and many others.

Along with these new, rich forests came an expanding diversity of pollinators and herbivorous insects, and with them, diversification of their insect predators, including these big-headed flies.

"With these new discoveries, we see that the early history of these oddly shaped insect predators provides a part of the puzzle revealing the broad ecological-evolutionary revolution of expanding predator-prey relationships and increasing biodiversity during the formation of new ecosystems," says Archibald.