Explanation for why we don't see two-foot-long dragonflies anymore fails
2 days ago
- #entomology
- #palaeontology
- #evolutionary biology
- During the late Palaeozoic era, giant insects like Meganeuropsis permiana had wingspans exceeding 70 cm, sparking questions about why such large insects no longer exist.
- The 'oxygen constraint hypothesis' suggested giant insects required high oxygen levels due to inefficient breathing systems, but this theory is now considered incorrect.
- Insects breathe via a tracheal system with spiracles, tracheae, and tracheoles delivering oxygen through passive diffusion in the smallest tubes.
- Diffusion's slow nature limits oxygen delivery to deep tissues as insects grow larger, potentially requiring more or wider tracheoles that could crowd muscle fibers.
- A structural tipping point exists where overly large tracheoles could impair flight performance by occupying too much space within muscles.