Warming up for flight

[Doug Dawn]

Sunsol Daniels wrote:

> Why do butterflies have to sit in the sun to warm up, but moths can fly
> without sunshine?
>
> Sally

Hi Sally,

Nothing too surprising when you think about it - moths are not optimized in
an evolutionary sense for the temperatures butterflies are if we try to
generalize.

Generally, I could think heat is regulated as follows in the insect:

1.-  Free source - Solar power.  The sun and warm rocks, etc. where wings
act as solar collectors  Recall butterflies can't fold their wings if they
want to, though moths typically do due to their niche optimization.

2.-  Internal source is the friction created in the contraction of flight
muscles (just like in humans, we shiver to keep warm and the molecular and
macro resulting friction in our muscles converts fuel into heat).  This has
been called "shivering thermogenisis".

3.- Another internal source of heat, especially for smaller insects are the
organs which increase "blood" temperature and "heart" which sends it to the
thorax where the flight muscles are.

4.- In butterflies, a lot more heat is lost in the abdomen than moths since
the moths typically have a better abdominal heat exchanging system to
deliver heat to their "blood".  In this case many moths have a more
efficient heat exchanger inn the abdomen which actually flows counter
current and provides heat to the thorax.  The thorax temperature is what
determines if the Lep flies since that is where the flight muscles are.  See
NOTE for further information on efficient abdominal heat exchange.

5.- As any air conditioning engineer might point out, "insulation" is
important.  "Regional endothermy" is the so called trait giving the ability
to maintain the little area of flight muscles warm.  Perhaps the "Thermos
effect" might be an alternate term.  Moths can be better insulated than
butterflies, but also see NOTE.

NOTE:  For more information on the benefits of counter current flow, look up
the Lorenz cycle (vs. Carnot) and check out my US patent #4,926,650 if you
want to understand better the efficiency for counter current heat
exchangers, where a practical method is described for achieving this for
industrial application.  But it basically says, when you don't use pure
fluids, the efficiency can be higher when the fluid to be heated and the
fluid to be cooled are closer in temperature.  Being closer in temperature
requires counter current flow of fluid mixtures:  i.e.  Heated fluid from
the abdominal matrix flows into the warmest part of the heat exchanger
between itself and the zone in it preparing the "blood" for thorax.  As the
transfer occurs within the abdomen, the temperature difference is minimized
and matched.  This minimizes heat escape, but a discussion like entropy are
off topic and has already happened once.  As this relates to the insect, the
exit end of the abdominal heat exchanger has maximized the heating ability
of the "blood" now destined to supply the thorax.

http://www.patents.ibm.com/fcgi-bin/any2html?FILENAME=%2Fcache%2F50%2F66%2F4926650.tif&PAGE=3&USER_HTML=%253CA%2BHREF%253D%2Forder%253Fpn%3Dus04926650__%253EOrderPatent%253C%2FA%253E&SCALE=0.35

I am guessing that butterflies do not have the counter-current heat exchange
option, at least during warm days, because at that point heat is a problem
to be dissipated any way it can including by the most inefficient heat
transfer.  I am practically sure someone knows experimentally this but if
not it would be a good subject for a research paper.

Keep in mind there are butterflies that do not even fly in the Sun
(crepuliscars like from the Smyrna genus).  And moths - like Sphinx moths,
which specifically have evolved to fly in the warm season do not have the
heat exchanger setup described above.  They effectively have efficient
cooling exchangers to quickly dissipate the heat buildup expected.  The
"aorta" is much like a set of cooling coils to dissipate heat  So as you can
see they are all in their individual niches and generalizing could cause
problems.  I suspect that day flying moths like Urania have also evolved the
generalized butterfly system.  Finally note, that moths can't just get up
and fly when it is cold and dark.  They have a revving up period which can
be as much as a half hour while the system described above heats them.  Not
a whole lot unlike butterflies basking in the morning sun which accomplish
the same means...And that same moth which does such a good job at on cool
season nights probably isn't around in warm seasons since it would "burn
out".  That brings up another interesting question:  What Lep has the
broadest range of temperature operation and what is its system like?  That's
a good one for an expert.

Hope this is helpful for your question and maybe someone else can clarify
further.  Best wishes.  Doug Dawn.
________________________
Douglas David Dawn
http://www.geocities.com/RainForest/4048/
Dawn Photo
http://members.tripod.com/dawnphoto/
N.  25º 37.408'
W. 100º 22.003'
Altitude 910 meters
Sylvania Pinus-Quercus