Hiding in the tundra...[theory?]

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 
physiological temperature. 

   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 
to Leps.

Best butterflying...Doug Dawn
Monterrey, Mexico

>                             Ken Philip
> 
> 
> 
> 
> 
> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.yale.edu/mailman/private/leps-l/attachments/20020806/9a02a51c/attachment.html 