Hiding in the tundra...[theory?]
MexicoDoug at aol.com
MexicoDoug at aol.com
Tue Aug 6 17:47:03 EDT 2002
Ken, Re: my question on the significance of the impact at northerly latitudes
lowering absolute atmospheric pressures was a little too much wishful
thinking to make it fit with the thread [theory?].
However how about comments in general on the concept of flight, lift, and
tired butterflies, the real point of my post without the Arctic addition? My
comments to your kind remarks follow your text.
En un mensaje con fecha 08/06/2002 2:00:49 PM Central Daylight Time,
fnkwp at aurora.alaska.edu escribe:
> > but it is also true that as you get further north, air pressures are
> > somewhat lower at the same altitude. By Alaska this certainly ought
> > to be noticable.
> Well, not very. The pressure difference due to the thinner atmosphere at
> high latitudes is a millibar or so, or around 1 per mil (= 0.1%)--and
> that applies for the same elevation _and the same temperature_, and also
> the same conditions regarding cyclones and anticyclones.
Based on your feedback, I'll bag the sub-arctic areas from my original
thinking, but that does not change the [theory?] significantly for temperate
latitudes. Please do keep in mind, that I mentioned two factors- total air
pressure (physics) and oxygen availability (physiological). Perhaps the
extra pressure you mention is caused by water vapor, and though I don't mean
to debate your local weather statistics.
> The North Slope lies at low elevations--the Arctic Coastal Plain
> is essentially at sea level. Furthermore, during clear summer weather the
> Slope often lies within the Polar High. Finally, air temperatures are
> cooler than in similar elevations at lower latitudes. The result is that
> atmospheric pressures are normally _higher_ than at lower latitudes at
> the same date.
OK, that a lot of water is available to add to the partial pressure of the
atmosphere is more likely here, raising your area pressures. I do want to
comment that my initial observations should have been obviously prefaced, "At
constant temperature..." so to remove this variable. At colder temperatures
butterflies here in Mexico frequently don't motivate to fly either, they will
hit the ground and hide, and it has less to do with pressure than with
By the way, note that a few years ago commercial airliners were
> unable to land at Fairbanks because a Siberian air mass had moved in, with
> no temperature inversion at all, and ground temperatures around -55F. The
> result was that pressure was so high that the planes' altimeters were
> reading off scale. Temperature wins as against the thinner atmosphere!
> According to the local Weather Bureau people, Alaska is one of the few
> places in the US where atmospheric pressure often exceeds 31 inches.
OK, I am and was definitely a believer that temperature wins against a
thinner atmosphere! I wasn't trying to explain the lift nor flight of
butterflies at -55F extreme, I am sure you know, in case any alien species
were on the wing. I was more interested in 6,000-12,000 feet at +65 F. And
perhaps that temp. is impossible in Alaska. As an aside, the trivia of the
insufficient altimeter design you described is quite interesting, though I
suppose could be deadly serious. While we are on interesting trivia, 1
millibar pressure difference you mention at higher latitudes...(at just 0.1%
per your post, how can I reconcile that with the commonly stated "fact" that
if Everest were at the same height as McKinley-Denali it would have an
oxygen/atmospheric? pressure equivalent of 3,000 feet higher than present and
be beyond the human ability to climb without supplemental oxygen? That is a
10% difference, 100 times greater than the insignificant amount you
mentioned, or is my logic wrong?
In my opinion, the tundra-hiding behavior of arctic butterflies>
> has nothing to do with atmospheric pressure--and everything to do with
> the obvious fact that there's nowhere else to hide. :-)
Well, thanks. I understand and agree with the rest of you post, but I would
definitely subject this last humorous statement to a little more vigor. As
far as I know, it is still greatly a puzzle as to how a butterfly manages to
fly regarding its coordination of energy, wing, muscular and aerodynamic
movements. The choice of hiding in the undergrowth vs. flying to safety
seems to me a lot more interesting and worthy of study to understand the
limits of flight. I don't buy the 'obvious fact' you propose, at all, that
there is _no where_ else to hide. On the contrary, I have been in many very
barren warm habitats except for easy hiding turf, were butterflies almost
invariably choose flight to hide. Except when I hit 6,000 feet or more, here
in Mexican latitudes, and the hiding starts. I have never chased a Dainty
Sulphur (_Nathalis iole_) below 3000 feet on a warm day and had it burrow.
But at 6,000 feet this has happened on a warm day. We also had Guy's example
from Turkish Tauruses (latitude N. 37.5-38.5 degrees) of hiding.
The obvious fact I would counter with is, butterflies that have to exert
themselves to the point of diminished flight response, at some point will
have better success at burrowing, when being pursued by enthusiastic
Lepsters, if that opportunity to burrow exists, right?:)
Further study of these types of limitations observed by many of us seem quite
promising to unravel the butterly flight dynamics (physiology & physics),
wouldn't you agree. Clearly experiments at constant pressure varying
pressure and oxygen partial pressure, and compressible gas partial pressure
now that you mention it sound like a real fun study.
Perhaps swapping habitats of butterfly individuals for species who extend the
range of both habitats and measuring resulting hiding frequency vs.
'controls' is worth a thesis, along will some measurements of insect
metabolism and wing deformation. Of course, in light of what you mention,
holding pressure constant and varying temperature will give a lot more data
points, but temperature affects might require more of an understanding of
physiology to deconvolute the data. I mention all the above as I find it
quite interesting that I claim to be a Lepidopterist, and honestly can't
easily name the first reason as to how our bugs manage to fly. [And I don't
mean, "flap their wings". I tried that and it doesn't work!] Quite a big
hole there, in my opinion since flight is such an interesting subject certral
Best butterflying...Doug Dawn
> Ken Philip
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