Giant Griffinfly: Earth’s Largest Insect Ever Discovered

In the realm of extinct creatures, a colossal representative of the ancient order of griffinfly-like insects emerges as the largest known insect species to have inhabited our planet.

A life-sized model of the Permian griffinfly, Meganeura. Image credit: Gene McCarthy

Modern times boast the atlas moth, wielding the largest wingspan among living insects at 160 cm² (25 in²), the white witch moth with its imposing wingspan of nearly 30 cm (12 in), and the goliath beetle, a heavyweight contender tipping the scales at 115 g (4.1 oz).

An intriguing trend observed across various animal groups is the historical prevalence of larger ancestors, and insects are no exception. Among these, giant griffinfly species such as Meganeura monyi and Meganeuropsis permiana stand out as the largest insect species ever documented. With wingspans reaching around 75 cm (28 in) – approximately three times that of the atlas moth – these prehistoric creatures held a notable presence. Their maximum body mass remains uncertain, with estimates ranging from 34 g to 240 g, surpassing the goliath beetle by twofold.

Atlas moths exhibit the largest wings, by surface area, among all extant insects. Image credit: Cocos.Bounty/Shutterstock

The audible crunch when squashing a cockroach, a sound some find oddly satisfying while others find distasteful, results from the compression and cracking of the exoskeleton. This phenomenon particularly manifests in cockroaches due to their exceptionally hard exoskeleton. In contrast, the exoskeleton of other insects may not exhibit the same rigidity throughout different body parts.

Interestingly, the wings of griffinfly species have been identified as their most resilient body parts, often being the ones that fossilize most effectively. Consequently, fossil records of griffinfly species often consist of fragmented specimens, punctuated by a few extraordinary exceptions.

A beautifully preserved fossil of Meganeuropsis permiana, the largest known insect to have existed. Source

Roaming the skies of Earth for over 20 million years during the Late Carboniferous and Late Permian periods (approximately 317-247 million years ago), griffinfly species achieved global distribution. Despite their diversity, with new species regularly described by scientists, not all were massive. Some remained within the size range of modern dragonflies, while others, like Meganeura monyi, attained truly gigantic proportions.

Meganeura monyi, initially described in 1895 based on a single fossilized wing measuring about 12 inches, boasted an estimated wingspan of approximately 27 inches (about 68.5 cm) and was hailed as the largest known insect of its time. However, in 1939, Frank Carpenter introduced Meganeuropsis permiana, described from an incomplete yet sizable wing discovered in two fragments. Carpenter estimated this species’ wingspan to be about 29 inches (almost 75 cm). Today, specialists consider both species of Meganeuropsis to be the same, adhering to the name M. permiana. This species holds the record as the largest known insect to have inhabited Earth.

Size comparison of the largest Carboniferous arthropods. Image credit: Emily Stepp

But why don’t we find such gigantic dragonflies in our modern world? What conditions allowed griffinfly species to attain such immense sizes?

The Late Paleozoic era in Earth’s history was characterized by unique features. During the Late Carboniferous and Early Permian, extensive coal swamp forests produced copious amounts of oxygen as a byproduct of photosynthesis, resulting in a hyperoxic atmosphere with oxygen levels far exceeding those of today.

As insects lack lungs, they breathe through a system of tubes (tracheae) connected to the outside. Oxygen diffuses across the walls of these tubes. With higher atmospheric oxygen levels, insects could absorb more oxygen, potentially allowing for the evolution of larger body sizes. Griffinfly anatomy suggests highly maneuverable flight capabilities, demanding significant metabolic activity and necessitating elevated oxygen levels.