Life › Seas, forests & the move to land › Insects: the first animals to fly
Giant insects (Meganeura)
c. 305–299 million years ago· Organism or group· Animals
Strong evidenceGood evidence; dates or details still being refined.
Griffinflies such as Meganeura, dragonfly relatives with wingspans near 70 cm, the largest insects known.
See it on the Life map →What happened
Meganeura monyi, found in 1880 in coal-measure rocks about 300 million years old at Commentry, France, had wings spanning roughly 65–70 cm. It and its relatives, the griffinflies, hunted other insects in flight. Meganeuropsis from early Permian Kansas was similar in size, and the millipede relative Arthropleura reached over 2 m long. Many scientists link this gigantism to high oxygen, perhaps 30% or more of the air, compared with 21% today.
Why it matters
A classic case of the environment setting size limits. Insects breathe through tiny tubes, so oxygen levels may cap how big they can grow.
Think of it like
Like a building limited by its ventilation design: tube-based air supply works well only up to a certain size.
The evidence (fossils, genes, rocks)
Wing fossils from France and Kansas; oxygen estimates from geochemical models such as Robert Berner's; experiments in which some insects, including dragonflies, grow larger in oxygen-rich air.
Still debated
Oxygen may not be the whole story. Before pterosaurs and birds, insects had no flying vertebrate predators, and which factor mattered more is debated.
Connections (2)
▸Carboniferous coal forests were home to Giant insects (Meganeura)Well established
The connection
The coal forests gave giant insects food, perches and warm, humid air. Vast plant growth and buried carbon are thought to have raised oxygen to perhaps 30% or more of the air, which may have let insects, which breathe through tiny tubes, grow far larger than any alive today.
When and how
Late Carboniferous swamp forests, about 305–299 million years ago; Meganeura comes from coal-measure rocks at Commentry in central France.
The evidence
Giant griffinfly wings occur in coal-forest deposits. The oxygen link rests on geochemical models and insect-rearing experiments: well supported, but not proven.
Debates and open questions
Whether high oxygen or the absence of flying predators mattered more is debated, and past oxygen estimates carry wide uncertainty.
▸Insects: the first animals to fly grew to record size as Giant insects (Meganeura)Well established
The connection
Late in the Carboniferous, some flying insects reached sizes never matched since. Meganeura, a dragonfly relative called a griffinfly, had wings spanning about 65–70 cm. A leading explanation is the oxygen-rich air of the time, which let insects' simple breathing tubes supply bigger bodies.
When and how
Coal-forest swamps about 305–299 million years ago; Meganeura fossils were found at Commentry, France, in 1880.
The evidence
Fossil wings from France and elsewhere, oxygen estimates from rock chemistry, and lab experiments in which some insects grew larger in high oxygen.
Debates and open questions
Oxygen may not be the whole story; the absence of flying vertebrate predators before pterosaurs and birds may also have allowed giants.