<![CDATA[How do flies stay cool on hot days if they can't sweat?]]>How do flies stay cool on hot days if they can't sweat? 🤨

They blow bubbles of watery saliva; some of it evaporates & loses heat; they then re-ingest the cooler liquid.

Simple 🤷‍♂️

Two flies seen at it this evening: a lesser dung fly (Sepsis fulgens; 🇩🇪 Glänzende Schwingfliege) & a fruit fly (Scaptomyza pallida; 🇩🇪 Taufliege).

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]]>https://board.circlewithadot.net/topic/f2074240-bf2c-4793-ba9f-8792ace94161/how-do-flies-stay-cool-on-hot-days-if-they-can-t-sweatRSS for NodeFri, 15 May 2026 05:57:59 GMTSun, 10 May 2026 18:05:55 GMT60<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Mon, 11 May 2026 07:34:48 GMT]]>@hans Thank you in return. I’m not sure how long this evaporative thermoregulation mechanism has been suspected, but the proof came via thermal-IR imaging as recently as 2018:

Mark McCaughrean (@markmccaughrean@mastodon.social)

For the discovery that bubble blowing helps with fly thermoregulation, see Gomes+18 who used thermal-IR imaging to observe blowflies doing it. Droplets cool by up to 8°C below ambient in just 15 secs under some conditions, & when re-ingested, it lowers the temperatures of the head, thorax, & abdomen by 1, 0.5, & 0.2°C, respectively. The fly repeatedly blow bubbles, to cool further, only losing a little at a time. Lots of other interesting details in the paper too 👍 https://www.nature.com/articles/s41598-018-23670-2

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]]>https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116554785663172798https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116554785663172798Mon, 11 May 2026 07:34:48 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Mon, 11 May 2026 07:32:27 GMT]]>@gregr Thanks 🙂 You took your lovely image a year before the Gomes+18 paper was published (see other posts in my thread), so it’s perfectly reasonable that you didn’t know 😉

]]>https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116554776441055790https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116554776441055790Mon, 11 May 2026 07:32:27 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Mon, 11 May 2026 07:30:28 GMT]]>@etp Thanks – that’s very kind.

The first image is effectively straight from the camera – just exposure & contrast tweaks, plus noise reduction, nothing else.

The second one is the same, except I had a slightly sharper image of the inside of the water droplet, so comped that into the other one. I doubt anyone would be able spot it, but since I had it, I thought I might as well use it.

Have been thinking about the thermodynamics overnight too & may post some more info 🙂

]]>https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116554768603069213https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116554768603069213Mon, 11 May 2026 07:30:28 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Mon, 11 May 2026 06:54:44 GMT]]>@markmccaughrean Astonishingly beautiful images and great science too.

]]>https://board.circlewithadot.net/post/https://indieweb.social/users/etp/statuses/116554628114763012https://board.circlewithadot.net/post/https://indieweb.social/users/etp/statuses/116554628114763012Mon, 11 May 2026 06:54:44 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Mon, 11 May 2026 02:39:12 GMT]]>@markmccaughrean Cool! Got one of those but didn't know for thermoregulation
https://images.gregr.fr/2017-05-06-yeched-mad.html

]]>https://board.circlewithadot.net/post/https://mamot.fr/users/gregr/statuses/116553623284827990https://board.circlewithadot.net/post/https://mamot.fr/users/gregr/statuses/116553623284827990Mon, 11 May 2026 02:39:12 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Mon, 11 May 2026 00:51:02 GMT]]> Vor einigen Jahren beobachtete ich solche Tropfen und hatte keine Idee wozu.]]>https://board.circlewithadot.net/post/https://instapix.org/p/hans/959253525133268196https://board.circlewithadot.net/post/https://instapix.org/p/hans/959253525133268196Mon, 11 May 2026 00:51:02 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Mon, 11 May 2026 00:04:06 GMT]]>@markmccaughrean
Fabulous pictures, and fascinating science. I had seen this behaviour before and wondered about it.

]]>https://board.circlewithadot.net/post/https://mastodon.social/users/robloblaw/statuses/116553013442469229https://board.circlewithadot.net/post/https://mastodon.social/users/robloblaw/statuses/116553013442469229Mon, 11 May 2026 00:04:06 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 23:18:39 GMT]]>@jussi Thanks – you never know how these things are going to turn out when you spot a tiny beast & struggle to get your tripod & camera set up before they scarper. But I’m happy with the results & glad that you like them too 🙂👍

]]>https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116552834734283630https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116552834734283630Sun, 10 May 2026 23:18:39 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 22:53:08 GMT]]>@markmccaughrean Cool science, but this is _gorgeous_ macro work!

]]>https://board.circlewithadot.net/post/https://sielun.romu.casa/users/jussi/statuses/01KRA1GA7W547E678D50XQF8FRhttps://board.circlewithadot.net/post/https://sielun.romu.casa/users/jussi/statuses/01KRA1GA7W547E678D50XQF8FRSun, 10 May 2026 22:53:08 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 21:11:44 GMT]]>@markmccaughrean

Whoa, it's really a pity that technique doesn't work for me, given the surface tension would be "slightly insufficient" to keep the required amount of liquid together… Imagine you were sitting in a café during summer time, pulling such a stunt… 😂

]]>https://board.circlewithadot.net/post/https://tldr.nettime.org/users/katzenberger/statuses/116552335671149271https://board.circlewithadot.net/post/https://tldr.nettime.org/users/katzenberger/statuses/116552335671149271Sun, 10 May 2026 21:11:44 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 19:12:10 GMT]]>For the discovery that bubble blowing helps with fly thermoregulation, see Gomes+18 who used thermal-IR imaging to observe blowflies doing it.

Droplets cool by up to 8°C below ambient in just 15 secs under some conditions, & when re-ingested, lowering the temperature of the head, thorax, & abdomen by 1, 0.5, & 0.2°C, respectively.

The fly repeatedly blow bubbles, to cool further, only losing a little at a time.

Lots of other interesting details in the paper too 👍

https://www.nature.com/articles/s41598-018-23670-2

]]>https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116551865504028078https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116551865504028078Sun, 10 May 2026 19:12:10 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 19:04:12 GMT]]>@katzenberger Thought as much: this paper by Gomes+ from 2018 did exactly that with a blowfly making water bubbles.

The droplet cooled by up to 8°C below ambient in just 15 seconds under some conditions, & when re-ingested, lowered the temperature of the head, thorax, & abdomen by 1, 0.5, & 0.2°C, respectively.

And of course the fly can repeatedly blow the bubbles, only losing a little at a time.

Lots of other interesting details in the paper too 👍

https://www.nature.com/articles/s41598-018-23670-2

]]>https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116551834183448197https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116551834183448197Sun, 10 May 2026 19:04:12 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 18:42:44 GMT]]>@u0421793 @futurebird Indeed, although bees use active air conditioning (their wings) to get evaporation going, while the flies are passive 🙂

]]>https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116551749776930526https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116551749776930526Sun, 10 May 2026 18:42:44 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 18:33:42 GMT]]>@katzenberger I'm sure someone has done it – perhaps a thermal-IR camera with a good lens could give a result.

]]>https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116551714253025388https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116551714253025388Sun, 10 May 2026 18:33:42 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 18:31:05 GMT]]>@markmccaughrean

Very cool (pun intended).

Would it be possible to measure the decrease in temperature?

]]>https://board.circlewithadot.net/post/https://tldr.nettime.org/users/katzenberger/statuses/116551703964145349https://board.circlewithadot.net/post/https://tldr.nettime.org/users/katzenberger/statuses/116551703964145349Sun, 10 May 2026 18:31:05 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 18:29:49 GMT]]>@futurebird@sauropods.win @markmccaughrean@mastodon.social this is the mechanism of how bees manufacture honey

]]>https://board.circlewithadot.net/post/https://toot.pikopublish.ing/notes/am3o95tb0v0m020whttps://board.circlewithadot.net/post/https://toot.pikopublish.ing/notes/am3o95tb0v0m020wSun, 10 May 2026 18:29:49 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 18:28:01 GMT]]>@markmccaughrean I got fascinated withspiracles recently, and it strikes me that this behavior re temperature and water takes advantage of some of the same geometry & math that make spiracles work for air/oxygen.

]]>https://board.circlewithadot.net/post/https://mastodon.social/users/slowenough/statuses/116551691902310094https://board.circlewithadot.net/post/https://mastodon.social/users/slowenough/statuses/116551691902310094Sun, 10 May 2026 18:28:01 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 18:26:54 GMT]]>@markmccaughrean

dipterans are so damn odd

They inflate their heads and eyes.

Just strange as can be.

]]>https://board.circlewithadot.net/post/https://sauropods.win/users/futurebird/statuses/116551687503943070https://board.circlewithadot.net/post/https://sauropods.win/users/futurebird/statuses/116551687503943070Sun, 10 May 2026 18:26:54 GMT<![CDATA[Reply to How do flies stay cool on hot days if they can't sweat? on Sun, 10 May 2026 18:11:17 GMT]]>That said, it wasn't particularly warm today, & less so this evening as the cloud rolled in. It was humid still though.

The Sepsis fulgens fly was going through a whole preening process at the same time as the droplet of water was hanging from its mouth, turning in circles, & cleaning its wings with its legs.

Then it sucked in the water droplet & flew off 🤷‍♂️

]]>https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116551626119836917https://board.circlewithadot.net/post/https://mastodon.social/users/markmccaughrean/statuses/116551626119836917Sun, 10 May 2026 18:11:17 GMT