Hiding in the tundra...[theory?]

[MexicoDoug at aol.com]

fnkwp at aurora.alaska.edu (Kenelm Philips) escribe:

Ken, this is the second set of comments I wanted to make, concerning the 
effects of higher altitude on organisms, without needing to consider how 
atmospheric pressure and oxygen availability varies with latitude extremes.   
 I might have titled it "Can a butterfly get tired?  and "Can a butterfly get 
tired especially at high altitude?" and "Under what conditions?".  Is there 
an answer to that?  My responses follow yours:

> I was more interested in 6,000-12,000 feet at +65 F.

Here's a quote from Mani's book: 'Ecology and Biogeography of High Altitude
Insects':

-"In the case of insects, however, the increasing oxygen deficiency of the
-air at high elevations does not seem to have any appreciable direct effect.
-Most insects are know to be extraordinarily resistant to not only extremely
-low atmospheric pressure, but also to rapid alternations of low and high
-atmospheric pressure."

-"Lutz exposed millipedes, _Drosophila_, beetles, butterflies and bees to
-low atmospheric pressure in the neighborhood of 1/10000 mm Hg for 90 se-
-conds without visible harm."


I haven't had access to even a copy of Scott for over a year since I last 
moved,  thanks for taking the time to look up a "hard" reference on high 
altitude on bugs.  My interpretation of the text indicates that the authors 
were really after hardiness/resilence of the insect body, when compared to 
vertebrates.  The source certainly indicates that insect bodies are able to 
withstand far more stress where vertebrate bodies might explode or at least 
sustain damage to vertebrates respiratory and other sensitive equilibrium 
determined metabolic systems.  While it is easy to imagine insects packed 
inside skeletons handling environmental extremes better than organisms with 
internal skeletons (evolution didn't face us with getting stepped on or 
clamped in birds' bills)  it is hard to see how that can extend to assuming 
insects at high altitude necesarily can fly with similar efficiency - at 
constant temperature - and relatively more efectively avoid Lepsters trying 
to chase them.  I see no reason to think the ability to fly is comparable 
with the ability to survive stresses in hostile environments.  Note, if 
temperature weren't constant, at constant pressure (altitude), a reasonable 
Lepping day, many species of Leps can no longer fly while we humans have no 
problem running around picking them up.  This speaks of the limitations of 
their flight metabolism worse than we vertebrates have at this reasonable 
Lepping and nectaring ambient range.  And certainly a millipedes and beetles 
are designed better to not get killed on impact at reasonable speeds when 
getting hit by cars, whereas butterflies are not, so while that is getting 
away from the authors stream of thinking on pressures, I think it is worth 
keeping in mind. 


-"Such experimental investigations do, however, emphasize the fact that
-insects are not likely to be directly influenced, to any significant effect,
-by the reduced atmospheric pressure at high altiutudes in the same way as
-Vertebrata are affected."

This seems to contradict what I just responded above, though I don't think it 
does, taking into consideration the authors' thinking.  It is a gross 
generalization and I wouldn't read too much into it.  That Vertebrates and 
insects are not affected in the "same way" is certainly not doubted, that 
most insects can handle more pressure stress than most vertebrates is not 
doubted. But walking and the respiratory support in humans, as a reference 
point, vs. flying and the supporting metabolism seem an order of magnitude 
different in effort.  Certainly an insect can probably happily burrow under 
conditions we suffer frostbite, but can those insects with reasonable ranges 
(which are not necessarily Sherpa-optimized) fly unaffected?  I would doubt 
that.  They are not superbugs and while evolution may have given cockroaches 
certain conserved advantages after being around 50 times longer than humans, 
and 6 times longer than Leps, I wonder how long butterflies have had to 
optimize to stresses unique to low-pressure/oxygen conditions?

-Insects in these tests seemed to function fine up to elevations of over
-17,000 meters--more than twice the height of Mt. Everest. Note that some
-species of _Parnassius_ live at 6000 meters elevation in the Himalaya.

17,700 meters (58,070 feet), twice Mt. Everest elevation?  The pressure there 
is only 9.146% that at sea level.  I seriously doubt any butterfly will 
"function fine", I.e., fly without a problem, at these elevations.  What does 
"function fine" mean?  I assume, succesfully breath at minimum activity.  And 
maybe an ant can walk around almost fine since under other conditions it can 
carry several times it weight easily.

The Parnassians at 6,000 meters (19,685 feet), presumibly flying, certainly 
present a challenge to understanding flight, and to the entire reasoning I 
have used, and possibly refute it, though I bet instead they probably present 
a wonderful opportunity to look for differences vs. other species which can't 
fly at these altitudes.  For one, their wings are probably extremely rigid as 
I believe the deformation of wings common to flight and especially takeoffs 
of of less use, whearas gliding on perfect wings at maximum efficiency might 
be more important.  It is interesting if they are white, as a darker color 
would act as a better Solar collector.  Or perhaps those only fly on Sunny 
days when, on the contrary, they collect more heat than they need to counter 
ambient temperatures (seem to recall a reference somewhere, Scott?, where 
some Parnassians were seen flying in cool snowstorms).  One thing I would 
bet, however, is that a Sherpa would be better at catching one of these bugs 
at 19,685 feet than I can photograph one at 4,000 feet in California.

-Now, as regards 'burrowing' behavior. I was referring to the way
-arctic butterflies will burrow into the tundra (and vanish) when they are
-under one's net. Same thing for scree. When they are being pursued, however,
-they will normally escape by flight. Oddly, it was only a couple of weeks
-ago that I observed a textbook case of escaping pursuit by abruptly drop-
-ping into low vegetation--and this was a _Speyeria zerene_ in Haines,
-Alaska, in coastal rain forest habitat. This was clearly a predator-eluding
-strategy: the drop was very abrupt just after the butterfly had changed
-direction--so that one's eye was led to look past the spot where it
-dropped. The same butterfly did this 4 times in row before it finally took
-off into the forest.

Nice set of observations!  Were you the predator?  Here there is no 
pressure-altitude effect, and it is first hand data, though you didn't 
mention whether it was 'warm' and 'Sunny' or not.  So I assume you mean to 
support that flight limitations are not the factors to consider when a bug 
does the burrowing, or at least drop to the ground maneuver.  It was a nice 
point you made in warning not to get carried away with any too much "catch 
all" explanations.  But a preponderance of first hand Lepster evidence seems 
to suggest that this burrowing-playing 'possum behavior is more prevalent at 
higher altitudes, at least in the experience of the field Lepsters of the 
list.  

-As regards butterfly flight, I believe the mechanisms involved are
-fairly well known now. They are rather complex--but no violations of
-physics are involved. The old claim that "science has proven that the
-bumblebee can't fly. The bumblebee, being ignorant of this fact, goes on
-flying." is based on a faulty model of insect flight, which assumed the
-wings are rigid. They aren't.

Yes, I also mentioned basically the same comments regarding "deforming and 
snapping wings" to provide lift and flight in my original post, an I am 
certainly not trying to doubt a bumble-bee!  On the contrary!  You add, 
though, that the physics of the mechanisms of (at least bumble-bee?) flight 
are well understood.  I would be indebted to you for any guidance on where to 
go for further information.  Specifically to see if any work relating ambient 
pressure and lift are gleanable from these models.  And I really doubt that 
respiration has been added to these physical models, so there may still be a 
lot of interesting new science to be done...

-It is quite possible that butterflies could chnage their predator-
-escape strategies at high altitudes. But I doubt that lack of oxygen or
-low air pressure is the main factor. After all, the same factors would
-influence their non-arthropod predators even more severely. I can't run
-down _Colias nastes_ at sea level--I wouldn't even _think_ of trying to
-run them down at 10,000 feet!
-Ken Philip

Well, I am pleased that you ever-so slightly restated your opinion here from 
"obvious fact of there being no where else to hide", to a more diplomatic 
"not a main factor".  While the _Colias nastes_ may have us soundly whipped 
under the conditions you describe, I bet Mark would give it the ol' college 
try.  I'll just mention that flying vs. walking around, or even running would 
seem not to be comparing apples to apples (due to the proportional 
consumption of flight), and whether the pursued or pursuor wins doesn't seem 
to be a given.  Some of this answer might be hiding in the fact as to what 
percent of resting energy a butterfly needs for flight vs. a human needs to 
run.  At both altitudes...

I would think that like all living organisms butterflies will have limits 
probably defined by their habitats, and some butterflies might just get the 
shorter end of the stick vs. us.  At least I would like to believe that on a 
hot day in the field when it is wishful thinking that a Lep will tire and 
pause long enough to smile for a photo before resuming to play non-stop tag 
with leaves and a enthusiastic photographer or collector who perpetually 
feels like he is "it". 

Best wishes...Douglas Dawn
Monterrey, Mexico
Elevation, 570 meters
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