Cicadas' unique urination unlocks new understanding of fluid dynamics | Hacker News Reader

Cicadas' unique urination unlocks new understanding of fluid dynamics

phys.org

84 pointsgmays23 comments

> However, while cicadas are easily heard, they hide in trees, making them hard to observe. As such, seeing a cicada pee is an event.

Here in the tropics, a tree that is full of cicadas will reliably have a steady "mist" of pee underneath its canopy, the ground will be damp, leaves of understory flora wet/shiny, and the air noticeably cooler than outside of the pee zone. Put a camera in the tree and I bet you can get footage easily.

Also observable in the US: https://www.washingtonpost.com/weather/2021/05/25/partly-clo..., https://www.thecut.com/2021/05/bad-news-cicadas-pee-a-lot.ht...

"Droplet superpropulsion in an energetically constrained insect"(https://www.nature.com/articles/s41467-023-36376-5 ) is a great paper from the same authors - I came across it last year when I was deep in a project involving droplet manipulation on superhydrophobic surfaces. Nature is wild!

Indeed. It reminds me of that species of planthopper whose rear legs have interlocking "gears", allowing the insect to jump with both legs together in perfect synchrony:

https://www.smithsonianmag.com/science-nature/this-insect-ha...

Nature is probably richer than we yet know with ideas for physical systems that would boggle our minds.

It made me very happy, for some reason, that people are systematically and thoroughly studying a subject as obscure as this (fluid dynamics of peeing in insects). I now question if research is happening on every single ridiculous notion that crosses my mind. I bet a bunch of people are actually interested enough in that computation that a field of study exists for it, that I know nothing of, and couldn't find out about if I tried. What all of actual fuck are people looking into?!

Reminds me of the first time a bought a mattress. The guy was 60 years old and had been doing it his entire life. I was blown away at the depth of knowledge one could have on mattresses and mattress technology.

Ive posted it before, but i once learned way more than i ever wanted to know about time, specifically time regarding computers, all to answer a question from the business side of "well why cant we have nanosecond time matching across 10+ systems", and the reason is, because its really really hard and really expensive. This wasnt for science either, it was for VR, making the request even more ridiculous, and putting me in an even deeper hole, finding out the minimum response time of the human brain and eyes. I could talk a lot about it, but most peoples eyes glaze over about 30 seconds in

i didn't think that video would be so interesting. so it is a volume constraint? why don't other bugs do this? just hold more liquid? or do they face other constraints that cicadas don't have?

Very curious.

constraints meaning those that would influence evolution ofc

Warning, the video is footage of cicadas peeing. It's not a physics diagram or animation of the fluid dynamics involved.

Why is this a warning? I'm very confused, is it somehow "inappropriate"?

Some people on this site could be triggered, aroused, or subject to monitoring and adverse action by their employer by viewing such content.

I hope you are joking but at this point I don't know anymore.

I mean, I wasn't offended, but I was also expecting a diagram and was a little surprised to just see high quality cicada piss footage.

Link to paper:

https://arxiv.org/abs/2403.02359

Thus, larger animals expel larger amounts of liquid in a brief period of time with high flow rates, resulting in an almost constant duration across large mammals (21±13 seconds) following the ‘law of urination’

Awesome. I've bookmarked this to read later, perhaps tonight if I wake up to have a pee.

21 +- 13 is stretching the definition of “almost constant.”

Yes, although I'll forgive them that for using the 'We' ratio unironically.

Contains a reference to an article

> The researchers published this challenge to the paradigm as a brief, "Unifying Fluidic Excretion Across Life from Cicadas to Elephants," in Proceedings of the National Academy of Sciences.

"Then, while doing fieldwork in Peru, the team got lucky: They saw numerous cicadas in a tree, peeing." scientists are weird

I thought that they pee in droplets for the simple reason that they don't have bladders.

To pee in a jet requires them to have an entire additional organ to store the pee before ejecting it.

Ig Noble winner if there ever was one, I bet.

[stub for offtopicness]

Note to self: Don't stand under trees this summer.

Impressive alliteration in the headline.

Reply on news.ycombinator.com