324-million-year-old fossil reveals how insects conquered land

The rise of complex ecosystems on land was one of the major turning points in the history of life. As organisms expanded beyond the oceans, terrestrial environments became home to increasingly diverse communities. Insects, which today make up the most species-rich animal group on Earth, eventually became central to these ecosystems. Yet important parts of their early transition from water to land have remained unclear.

An international team of researchers has now identified a stem group insect from the Late Mississippian period, about 324 million years ago. By studying this fossil alongside other puzzling specimens from much earlier and later periods, the researchers reconstructed a critical stage in early insect evolution.

Their findings suggest that insects did not become fully terrestrial immediately after beginning to colonize land. Instead, early forms retained and modified features inherited from aquatic ancestors, spending an extended period in a semi-aquatic, amphibious way of life.