The Amazing Butt of the Dragonfly Nymph

The dragonfly is an amazing creature. Like sharks, dragonflies have changed very little since they first appeared during the Carboniferous era.

And the nymphs are equally if not more amazing than the adults, because these tiny critters could do a lot of things using their BUTT.

Image: blog.cat.org.uk

Dragonfly nymphs are ferocious predators. They feed on other aquatic insects, other nymphs, small fish and even tadpoles. But their prey items are often fast-moving creatures themselves, and so the nymphs have to act quicker.


Dragonfly nymphs have a functional lower lip called labium, and it can be extended to incredible length to snatch food. The ability of the labium to perform this fascinating act is closely related to its anus.

Image: bugs.bio.usyd.edu.au

The nymph draws water in through the anus, clenches, then compresses its abdominal and thoracic muscles against the water-filled rectal chamber. This raises the pressure of the internal body cavity, and pushes the labium out –in a strike that lasts 10 to 30 milliseconds. The amount of internal pressure generated is about 6000 Pa, or 6 kPa; equivalent to 0.87 psi. -- wired.com

That doesn’t seem like a lot, until you put it into human perspective. A typical dragonfly nymph weighs only 0.1g, and when you convert it into human form you'll get a 58kg man generating 555930 psi. Note: I pump my car tyres with only 32 psi of pressure.

A dragonfly nymph rectum can also help the animal move through the water, pretty much like the jet-propulsion of an octopus.

A nymph devouring a tadpole. Image: www.lifeinfreshwater.org.uk

By un-clenching their rectum, water in the rectal chamber can be jetted out at high pressure, pushing the nymph forward through the water. The forward thrust generated is 1.5 g in 0.1 second; nymphs’ top speed is 10cm/second. -- wired.com

Again, doesn't seem like much, but when you consider that a nymphs is only 2.5~6.0cm long; that's moving at four times its own body length in a second. Convert it to human form, you'll get a 1.8-meter-tall man moving at 7.2m/second (25km/hour) all with the thrust generated solely through his butt.

If this isn't amazing(-ly funny), I don't know what is.

Malcolm