Hiding in the tundra...[theory?]

[MexicoDoug at aol.com]

En un mensaje con fecha 08/05/2002 11:57:16 PM Central Daylight Time, 
fnkwp at aurora.alaska.edu escribe:

Ken & Mark, et. al,

I remember once trying to photograph what I believed to be an _Icaricia 
lupini_ (Lupine Blue) in a quite high mountain meadow in the Cascades of 
Washington State (6,800 feet).  As I pursued, my victim gave me a cold 
shoulder: it executed a number tricky manuevers including lethargic milk runs 
to the next convenient plant, and falling to the ground and semidisappearing. 
 True, Mark's observations at 12,000 feet were much higher, 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. Perhaps the 
latitude effectis not too significant but I hope some of the physicists on 
the list can criticize the following attempt at a contributing explanation to 
this adaptative behavior in such environments, brought to our attention by 
Mark:  

"LIFT" and "FLIGHT" for butterflies.

- At 6,800 feet and 47 Degrees North latitude on a nice, warm summer day, 
VERY unscientific sample of one (or a few), burrowing manuevers were 30/70 to 
skipping-out flight manuevers.

- At  12,000 feet and 38.8 Degrees North Latitude on a nice soon to rain 
summer day it appears that the burrowing manuevers are more common from 
Mark's text, than the 30/70.  And on the Alaskan slopes they burrow through 
rocks as seen by Ken:).

- Air pressure is about 55% that of sealevel at 12,000 feet, let me guess 
that this roughly will translate to 55% the lift for a spooked butterfly 
using equivalent force as one at sea level with firm wings (e.g., 
Papilionadae).

- Smaller butterflies, (like Lycaenidae) probably depend more on the "snap" 
caused by near thorax wing deformation to initially generate the lift 
necessary to ascend initially upon take off.  Thus their acceleration efforts 
will be significantly less than the 55%, probably on the order of 30%. 
(square of the 55%)

- Oxygen uptake for muscle function if aerobic respiration, at 12,000 feet 
and 38.8 degrees N. may drop to about 80%, based on human aveolar oxygen 
saturation, a poor, nonetheless worthwile reference point.  This could 
attenuate the available flight energy an additional "20%" or more depending 
upon their energy conversion efficiency for the butterflies.  And the 
saturation may take longer to achieve at these pressures and "deficits".

- While alpine-tundra butterflies are undoubtable more evolved for their 
environmental conditions, the basic premises above will have a strong impact 
and the basic laws of physics not violated.  And I am not so sure that the 
evolution would be so dramatic in many cases, because, the ranges of many of 
these butterfly species include less austere conditions in many cases.  

- Of course, with a possibility of only 20% - 40% the energy-lift available, 
I might decide to adapt, hiding by burrowing into the ground - if I were a 
butterfy being pursued on "The Far Side".  And we think walking is 
complicated, imagine how hard they have to work to fly!

Mark congrats on bringing your son with you, no doubt the experience through 
his senses is nothing short of envious and will be remembered for a 
lifetime...

Ken, you did study physics at one time, so please give me a hand here with 
your opinion...

Best...Doug Dawn
Monterrey, Mexico


> Mark Walker commented, re Rocky Mtn. tundra collecting:
> 
> > Arctic Lepidoptera seem to be well equipped for falling at a whim and
> > disappearing into the darkest depths of the arctic meadow landscape.
> 
>     They do indeed. Many times I have had a specimen under my net, and
> have been unable to find it. The underside color patterns are amazingly
> good camouflage, and the butterflies crawl way down into the vegetation
> and appear to vanish.



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