Fossil Insects In 2008, researchers at Tufts University uncovered what they believe is the world's oldest known full-body impression of a primitive flying insect, a 300 million-year-old specimen from the Carboniferous period. The oldest definitive insect fossil is the Devonian Rhyniognatha hirsti, from the 396-million-year-old Rhynie chert. It may have superficially resembled a modern-day silverfish insect. This species already possessed dicondylic mandibles (two articulations in the mandible), a feature associated with winged insects, suggesting that wings may already have evolved at this time. Thus, the first insects probably appeared earlier, in the Silurian period.
Four super radiations of insects have occurred: beetles (evolved about 300 million years ago), flies (evolved about 250 million years ago), and moths and wasps (evolved about 150 million years ago). These four groups account for the majority of described species. The flies and moths along with the fleas evolved from the Mecoptera.
Green River Insect Fossils Rare Beetle, fly larvae & Weevil fossils from Parachute Creek member, Green River Formation, Garfield County, Eocene age (48 MYO), See the photo for scale. The insects are preserved within a fine limestone, which formed at the bottom of vast lakes. When insects and plants died, their remains gradually sank down to the thick and murky, oxygen poor layer at the bottom of the lakes, and were preserved for eternity.