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Size limits on dragonflies
by
Stephen W. Hurrell
by
Stephen W. Hurrell
Abstract
Dragonflies are obviously limited in size by physical constants during flight. However, various studies on dragonflies have shown that the exact physical mechanism limiting their size is still unclear. This paper shows that increasing dragonfly size would increase the stress levels in the wing. The increasing wing stress must exceed the maximum allowable stress in the wing tissue at some point and the wing would begin to fail if the dragonfly became any larger. It is proposed that failure of the wing is the true physical size limit for dragonflies.
Suggested Citing Format
Hurrell, S.W. (2022). Size limits on dragonflies. Dinox.org
Page updated 11 Mar 2025
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Florian Nachon on Facebook. Insect size is also limited by oxygen level because their respiratory system is not very efficient. You need both low gravity and high oxygen level to reach this size.
Stephen Hurrell. Yes, it is commonly suggested that a high oxygen content is needed for insects to grow large. But after the Carboniferous oxygen level reduced. Nel et al (2008), The Odonatoptera of the Late Permian, detailed several large dragonflies during this period of low oxygen. This would contradict any relationship between size and oxygen concentration.
Vedat Shehu - Florian Nachon; What about the atmosphere's density?
Bill Erickson on Facebook. Have you seen the recent (2021) film version of DUNE. The characters fly helicopter-like aircraft called "ornithopters," which are based on the dragonfly design. I loved them even though I realized that they were probably physically impossible. As always, it's a problem of scale.
https://www.youtube.com/watch?v=VeOLDSunFWo
https://www.youtube.com/watch?v=VeOLDSunFWo
Stephen Hurrell. Yes, I love the "ornithopters" as well. I think they were in the original Dune book if I remember correctly. Interestingly, standard helicopter theory predicts a size limit as a power function and this was originally assumed to apply to dragonflies. However, Marden (1987) found this wasn't true for dragonflies - all dragonflies lift capacity tracks their mass. So if the same was true for an "ornithopter" power shouldn't be a problem. The limit would be the strength of the wing and since we could use stronger materials the size limit would be higher. We might well be able to build large "ornithopters" about the size of a helicopter.
The real problem with designing an "ornithopter" would be the control of the wings. Dragonflies have members that are thought to act as gyroscopes to provide positioning information that then controls the wings. It would certainly be an interesting engineering problem!
Ramin Amirmardfar on Linkedin
Ramin Amirmardfar on Linkedin
Why insects have small bulks?
https://www.linkedin.com/pulse/new-theory-why-insects-have-small-bulks-ramin-amirmardfar/
https://www.linkedin.com/pulse/new-theory-why-insects-have-small-bulks-ramin-amirmardfar/
Relationship between the power of the blood/fluid circulatory system and size of animals and plants
https://mardfar.webs.com/sizeofanimalsplants.htm
https://mardfar.webs.com/sizeofanimalsplants.htm
