Insects of a Lost World

The Permian period was a time of enormous change for insects. It began with the continuation of the Carboniferous pattern — diverse insect faunas in forested environments, with some truly giant species still present — and ended with the most catastrophic mass extinction in Earth's history. Between these two extremes, insects underwent rapid diversification, with many new groups appearing, including the first insects to develop complete metamorphosis.

The Permian World

During the Permian, the continents were assembling into the supercontinent Pangaea. This had major effects on climate: continental interiors became increasingly arid, and the vast coastal swamp forests of the Carboniferous gradually disappeared, replaced by drier forest types dominated by conifers, seed ferns, and ginkgoes.

Atmospheric oxygen, which had peaked at around 35% in the Late Carboniferous, declined significantly during the Permian, falling to perhaps 15% by the end of the period. This decline is thought to be one reason why giant insects became less common during the Permian, as lower oxygen levels made it harder for the tracheal respiratory system to support very large body sizes. See Oxygen and Gigantism for a detailed discussion.

Insect Diversification

Despite the changing conditions, the Permian was an enormously productive time for insect evolution. Many modern insect orders either originated or diversified significantly during this period.

Meganeuropsis permiana, from the Early Permian of Kansas, holds the record for the largest flying insect ever known, with a wingspan estimated at up to 71 cm. This giant griffinfly represents one of the last of its kind — the Meganisoptera declined through the Permian and were extinct by its end.

The Protelytroptera appeared during the Permian. These insects had hardened forewings similar to the elytra of modern beetles, though they were not true beetles. They represent an early experiment in wing modification that paralleled what beetles would later achieve independently.

The Permian also saw the possible first appearance of complete metamorphosis (holometaboly) — the developmental pattern where insects pass through a larval stage, a pupal stage, and then emerge as adults. This innovation, discussed further in Complete Metamorphosis: Origins, would eventually become the dominant life strategy among insects, used today by beetles, flies, butterflies, wasps, and many other groups.

The Elmo Limestone in Kansas is one of the most important Permian insect fossil sites, yielding thousands of well-preserved specimens representing dozens of species.

The Great Dying

The Permian ended with the Permian-Triassic extinction event approximately 252 million years ago — the most severe mass extinction in the history of life. An estimated 90-96% of all marine species and about 70% of terrestrial vertebrate species disappeared. The causes are thought to include massive volcanic eruptions in what is now Siberia (the Siberian Traps), which released enormous quantities of carbon dioxide and sulfur dioxide, triggering extreme global warming, ocean acidification, and widespread anoxia.

The effect on insects was devastating. Several entire orders went extinct, including the Palaeodictyoptera, the Megasecoptera, the Diaphanopterodea, and the Miomoptera. The Meganisoptera (giant griffinflies) also disappeared. Estimates suggest that insect diversity at the family level dropped by about 60% across the Permian-Triassic boundary.

However, insects as a whole survived. Many of the lineages that made it through the extinction — beetles, flies, various hemipterans — went on to become the dominant insect groups of the Triassic and beyond. The Great Dying fundamentally reshuffled which insect lineages would dominate, clearing ecological space for new groups to radiate. See Mass Extinctions and Insects for more.