If the new study is valid, there is \u201cno physiological reason why insects the size of griffinflies could not fly in today\u2019s atmosphere,\u201d the researchers wrote in a column about the work for The Conversation<\/a>. \u201cAnd yet they don\u2019t exist today.\u201d<\/p>\n The giant bug-o-sphere <\/p>\n According to the new paper, it\u2019s a \u201cbroadly accepted paradigm that oxygen enabled the evolution of complex life.\u201d That led researchers to consider whether levels of oxygen in the atmosphere, which has changed<\/a> throughout Earth\u2019s history, would effectively \u201cconstrain\u201d the evolution of body size for different species.<\/p>\n Throughout the 20th century, researchers discovered multiple fossils of giant insects with incomprehensibly wide wingspans. One of these was the griffinfly<\/a>, which was later found to have lived in a time when Earth\u2019s atmospheric oxygen levels were 9% higher than that today.<\/p>\n At the time, it made a lot of sense to assume that the two variables\u2014the griffinfly\u2019s size and higher oxygen levels\u2014were connected, since the giant bugs \u201crequired these high external oxygen levels to power the rapid burn of energy during flight,\u201d the team wrote in its column. Staying airborne requires that the flier defy gravity, so to speak, and the \u201crate of oxygen consumption increases roughly in proportion to the weight of the flier,\u201d the researchers added.<\/p>\n Untapped flight potential <\/p>\n But the team wondered if insects could self-supply that oxygen demand, given how they have a unique biological, tree-like mechanism called the tracheal system<\/a>. This structure delivers oxygen to insect flight muscles via a network of air-filled tubes called tracheoles, the development for which previous research confirmed was \u201cheritable\u201d and \u201chighly plastic,\u201d the paper noted.<\/p>\n The team arrived at this hypothesis during a separate investigation on the flight muscles of locusts, which revealed that tracheoles took up a measly 1% of the muscle fibers. The researchers then measured 44 species of flying insects across different sizes, taking 1,320 microscopic photos over five years.<\/p>\n ![\"Electron](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/03\/electron-microscope-images-flight-muscles.jpg\")
Under the electron microscope, thin slices of insect muscle (left) and mammal muscle (right) show the tracheoles and capillaries in white. \u00a9 Antoinette Lensink and Edward Snelling <\/p>\n