Tiny Flies Offer Clue to History of Land Masses

Millions of tiny flies living in special habitats all around the world may hold the key to some of Earth’s best-kept secrets about how the continents were formed.

A theory, being advanced by an insect specialist, may provide biological evidence for an idea advanced years ago by geologists--that the world once consisted of a great supercontinent that broke into the land masses known today.

“I think this is another piece in the puzzle of the grand scheme of things,” said Charles Hogue, entomology curator at the Los Angeles County Natural History Museum.

“These flies are an ancient group that have come down to us from the Permian Age roughly 250 million years ago,” he said. “They still have the same basic structure, so we know that we are dealing with a continuous line.”

Earth’s Early Inhabitants

Hogue thinks that the flies, known as gnat-winged midges, once lived on the supercontinent of Pangaea where, together with other simple life-forms, they made up the first communities of Earth’s living inhabitants. These were the days before the evolution of big-brained mammals.

The tiny midges thrive only near freshwater streams and waterfalls, and oddly enough, outside of such habitats they die within an hour, the entomologist said.

“I am postulating that they never moved across ocean groups; they cannot exist away from a stream. Even if people wanted to move them from place to place, they wouldn’t live because all of their stages are so closely adapted to stream conditions.”

Because of midges’ ancient roots and special requirements for survival, when the land masses broke into the continents and drifted apart, the midges, fragile wisps of life that they were, drifted with them.

150 Million Years Ago

The idea of continental drift was first postulated by geologist Arthur Wegener in 1912. Since that time it has been believed that Pangaea existed from about 300 million years ago until it broke up around 150 million years ago.

With Wegener’s model of the world in mind, one would be able drive from New York to Morocco and veer northeast to Spain or travel from southwest Africa to a warm and dry Antarctica (the ice ages had not yet occurred) and onto Australia without once touching water.

Wegener’s theory was revised about a decade ago when geologists suggested that ancient rocks that became frozen preserve their magnetism, a telling feature that lets scientists know approximately when and where they formed.

Shorter Time Period

Such findings lent credence to the existence of Pangaea, although some scientists now contend that the supercontinent may have existed for a much shorter geological period.

But after 20 years of searching, Hogue has located the flies on virtually every major land mass. He has not found the midges in extremely cold climates, nor has he found them on any Pacific islands, volcanic land masses that developed after the supposed existence of Pangaea.

“They’re the closest to being one of the best biogeographic indicators that we have of continental drift theory,” Hogue said. “These flies are like markers and I think they give us some clues about the past position of the continents.”

Perhaps more important, he says, the largest distribution of the midges have been found along the southern tips of South America, Africa, Madagascar and Australia, a continuum that he believes illustrates a previous connection.