A "Cool" Fly - a photo on Flickriver

A "Cool" Fly

My best photos are here: www.lacerta-bilineata.com/ticino-best-photos-of-southern-...

Blue Blow Fly | Calliphora vicina | Monteggio (CH) | May 2021

More TICINO/TESSIN Wildlife Photos (all taken in my garden in Monteggio/Ti, Switzerland): it.lacerta-bilineata.com/ramarro-occidentale-lacerta-bili... (the website exists in ESPAÑOL, FRANÇAIS, ITALIANO, ENGLISH, DEUTSCH)

My latest ANIMAL VIDEO (warning, it's a bit shocking): www.youtube.com/watch?v=4T2-Xszz7FI

ABOUT THIS PHOTO:
At first I wanted to title this photo "My Portrait In A Fly's Vomit" because upon closer inspection of the photo I discovered my own reflection on the tiny droplet of (what I assumed to be) puke that hangs out of the fly's mouth - and also because I just thought this was a really cool title (as you might have guessed, I'm probably not the most mature of people ;-)

But then I wanted to know what that droplet really was, because I photographed quite a few flies with this kind of "bubble" in front of their mouths, and since I wasn't sure about the puke, and scientists are adamant that flies don't chew gum, I had to get at the bottom of this (sligthly disgusting but still very intriguing) mystery.

Turns out, researchers only discovered relatively recently why certain flies and other insects like to have a droplet of saliva (because that's what it actually is) hanging out their mouths, and it's for a really interesting and quite practical reason: they use that "spit bubble" to cool themselves.

Here's a summary of an article published in the journal "Scientific Reports" from 2018: "Humans sweat to cool their heated bodies. blow flies have developed a different, unusual method for this purpose, but it is based on the same physical principle: They let a large drop of saliva hang from their mouths, which cools as some of it evaporates. By then reabsorbing the drop, they lower the temperature in the front part of the body.

It was already known that some flies temporarily secrete a drop of saliva, let it hang out of their mouths and then take it up again - repeating the whole process up to six times. But for most, this process was related to the digestive process.

Now temperature measurements by infrared imagers showed that a drop hanging from the "lick trunk" of a fly can cool as much as eight degrees below ambient temperature within 15 seconds. After the droplet is sucked in for the first time, the temperature in the head region drops by about one degree. If the process is repeated, the temperature there drops by as much as three degrees, and in the chest region by another 1.6 degrees.

"The large amount of energy required to evaporate water provides living creatures with highly effective ways to lower their body temperature," write the researchers led by Guilherme Gomes of the University of São Paulo and Denis Vieira de Andrade of São Paulo State University. For example, sweating evaporates water from the moist surface of the body, cooling the skin.

And by panting, dogs and other animals release excess heat by increasing water evaporation on the mucous membranes of the upper respiratory tract. The chitinous exoskeleton of insects, on the other hand, makes effective sweating difficult. Their tracheal system, which serves respiration, is also less suitable for cooling."

But apparently, letting a large bubble of drool hang out of their mouths, then sucking it in only to let it out again, and then constantly repeating that process, works perfectly well for flies. I tried to apply this cooling technique myself the other day (I work at an airport, the air condition was down, and it was really hot - and I was bored... what can I say). Well, I do not recommend it; it might have worked, but the horrified looks on the passengers' faces (not to mention my superiors') were enough to convince me to end my "fly-cooling-technique" experiment somewhat prematurely and put my mask back on ;-)

ABOUT THE SPECIES (from Wiki slightly abbreviated by me):
Calliphora vicina - the blue bottle fly - is a member of the family Calliphoridae, which includes blow flies and bottle flies. These flies are important in the field of forensic entomology, being used to estimate the time of a person's death when a corpse is found and then examined. It is currently one of the most entomologically important fly species for this purpose because it arrives at and colonizes a body following death in consistent timeframes.

The species predominates in Europe and the New World, but has found its way into other countries via harbors and airports. It was first recorded in South Africa in 1965 when a specimen was collected near Johannesburg, but specimen collections have been few and sporadic since then. It also occurs as an exotic in Australia and New Zealand.

Taken in: Switzerland / Ticino / Monteggio (show map)

Taken on: May 15, 2021

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Camera: Sony DSC-RX10M4, f/4.0, 1/250 sec, 220mm, ISO 125 (more info) (hide info)

Camera:	Sony DSC-RX10M4
Aperture:	f/4.0
Exposure Time:	0.004 sec (1/250)
Focal Length:	220mm
ISO:	125
Exposure Bias:	0 EV
Flash:	Off, Did not fire
Exposure Program:	Program AE
Exposure Mode:	Auto
Metering Mode:	Multi-segment
White Balance:	Auto
Contrast:	High
Color Space:	sRGB
Software:	DSC-RX10M4 v2.00
Show full info

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