Dragonflies and Damselflies

[ISv]

Great photo’s!

This is the obelisk posture, to minimize the area exposed to the sun and prevent overheating.

See: https://en.wikipedia.org/wiki/Obelisk_posture

Without knowing the species behavior the explanation "to minimize the area exposed to the sun and prevent overheating" could be misleading for the Obelisk posture: see the link you posted!

 

[Maximilian]

@Maximilian recently posted some pictures of a large white-faced darter or yellow-spotted whiteface (Leucorrhinia pectoralis) in the obelisk posture and has changed his profile picture.

See: https://www.canonrumors.com/forum/threads/dragonflies-and-damselflies.35543/post-1047073

Thank you for noticing and mentioning the change of my profile photo.
I am sure, I will return to the drinking barn swallow someday but that whiteface is IMO one of my best and important (protection of species) photos in 2026.
I recognized that obelisk posture with several dragonfly species, like common and ruddy darters as well. You mentioned in your posts above that a lot of species do it.

 

[Maximilian]

Am I the only poster here who, despite having a great deal of familiarity (and comfort) with the 'metric' system of measurements, prefers the Fahrenheit scale (over the Celsius scale) for discussion of everyday temperatures?

In a way, the Fahrenheit scale is sort of 'metric-y' in that I daresay that the vast majority of humans on earth (?) live in regions where the temperatures generally range from 0-100 degrees Fahrenheit (two powers of ten!).

To answer your question:
It depends on with which system you grew up.

For me as a German and Continental European the Système international d'unités (SI system) is the one to choose And Celsius is closer to Kelvin than any else.

I teach technical training courses where physical calculations are part of everyday work. For customers from every part of the world.
I keep repeating, like a mantra, that you always have to check the units if you don’t use the formula on a daily basis.
When it comes to temperature scales, I always joke that it just depends on which liquid you consider more important in life:
whether it’s water (Celsius) or ethanol (Fahrenheit and Réaumur).
(disclaimer: I know that this is physically not correct. But jokes don't have to be correct )

 

[AlanF]

To answer your question:
It depends on with which system you grew up.

For me as a German and Continental European the Système international d'unités (SI system) is the one to choose And Celsius is closer to Kelvin than any else.

I teach technical training courses where physical calculations are part of everyday work. For customers from every part of the world.
I keep repeating, like a mantra, that you always have to check the units if you don’t use the formula on a daily basis.
When it comes to temperature scales, I always joke that it just depends on which liquid you consider more important in life:
whether it’s water (Celsius) or ethanol (Fahrenheit and Réaumur).
(disclaimer: I know that this is physically not correct. But jokes don't have to be correct )

Everything in this thread has to be correct.

 

[AlanF]

I just had a visitor in my kitchen, who was quite difficult to remove. He ignored all the signs. I suppose the Southern ones can't read.

 

[P-visie]

EDIT #2 (a comment and a question):

Am I the only poster here who, despite having a great deal of familiarity (and comfort) with the 'metric' system of measurements, prefers the Fahrenheit scale (over the Celsius scale) for discussion of everyday temperatures?

In a way, the Fahrenheit scale is sort of 'metric-y' in that I daresay that the vast majority of humans on earth (?) live in regions where the temperatures generally range from 0-100 degrees Fahrenheit (two powers of ten!).

To add to @Maximilian’s answer: The US is the only large country that uses the Fahrenheit scale. Only 11 countries exclusively use Fahrenheit and 8 countries use Fahrenheit next to Celsius.

Source: https://worldpopulationreview.com/country-rankings/countries-that-use-fahrenheit

 

[AlanF]

I thought I had better go out and do some DIF after the Southern Hawker (R5ii + RF 100-500mm). Four-spotted Chaser, Ruddy Darter, and Blacktailed Skimmer.

 

[josephandrews222]

Good comments here. Where I reside, the temperature is almost always between 0 and 100 degrees Fahrenheit...nice round numbers.

And...in my head, when the temperature reaches 100, it is 100% hot, and when it dives to 0, it is really, really cold (0% hot).

So 0-100 works for me, in this narrow context.

I always enjoy teaching the nuts and bolts of the Kelvin scale (in particular its importance in various constants), and this morning learned something new (to me):

However, the kelvin has been redefined in terms of the Boltzmann constant, which relates the amount of thermodynamic energy in a substance to its temperature. When the revised SI was approved in November 2018, the new definition became:

The kelvin, symbol K, is the SI unit of thermodynamic temperature; its magnitude is set by fixing the numerical value of the Boltzmann constant to be equal to exactly 1.380649 × 10-23...J K-1[joules per kelvin].

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EDIT...rest of this post has been moved to where it belongs