Vanessa at night

[Ron Gatrelle]

snip
>
> It is not possible to prove a negative.

snip

Paul's solicitation of information relative to butterfly flight at night
(in the dark) in conjunction with his field-observations-based conclusion
that they do not fly in a sustained, directional,  migratory (or dispersal)
manner in the dark is not trying to prove a negative (hypothetical).  It is
a conclusion reached through that which is plainly observable.

How do we know the Miami Blue is in trouble?  Because we _see_ they are
_not_ there.  It would be ridiculous for someone or group to come along and
tritely dismiss the move to protect and prosper the Miami Blue by saying:
"How do they know that there are _not_ Miami Blues all over - one can not
prove a negative.  Just because they don't see them does not mean that they
are not there when no one is looking."

The reason I know there are no orange trees in my yard is that I _do_   not
see any there.  The _do_ makes this a positive (factual, actual, real)
conclusion based on _observable_ facts.  This is how we _know_ that a tree
falling in a forest generates sound whether or not there is a human ear
there to hear it or not.  (Yet, there are probably some intellectually keen
people in this world that are so dumb they would have to set up an
"experiment" - with a million dollar government grant of course- to fell a
tree remotely from 10 miles away with video cameras in place at the tree's
location to observe the reactions of several confined rabbits, deer, and
raccoons at the moment the tree hit the ground.  But this too would be
inconclusive as perhaps it was sight that startled the animals and there
was only a false conclusion reached.  Thus, the experiment would need to be
carried out again with blindfolded animals.  There are inconclusive factors
here too, so that ultimately one would have to find Dr. Do-little and have
the animals report directly to him.  But then how are we to know the
creatures are telling the truth?)

Now, Paul's (as probably all or our) observations are very limited so there
is a wide open door for some further testing, which, with the advent of
night vision technology makes observing leps in the dark very easy.  One
could tell fairly easily the vast majority of moths in flight from
butterflies in flight.  As others have suggested here - there is a student
project waiting for someone to do it ( if it has not yet been accomplished
yet).  However, this will be a waste of money as the answer is already
known as evidenced by our _seeing_ that the clouds of thousands of XX which
have been moving across the desert floor, the highway, and onto the car
windshields and grills has now completely stopped as we stand on the same
spot by the side of the far-from-human-lighting road at midnight.  And as
the sun comes up again the next day - slowly they return to the sky and
repeat the second day the dispersal of the first. And perhaps the third,
fourth, and fifth DAY -  then they are gone.

For decades I have seen most butterflies in the field fly till the last bit
of light.  I, like many others, have seen butterflies attracted to
(confused by) artificial light - with some types showing up much more
frequently than others.  However, none of this has anything to do with the
question as to whether butterflies (Pierids and Nymphalids in dispersal or
Monarchs in migration) engage in this activity (and by necessity have done
so for a few thousand years) _in the dark_  of the dead of night.  My
answer in no, they do not.  IF they did this would already be well
documented by people seeing clouds of them at night.

We are not talking about a couple individuals flitting about after dark for
some unknown unusual reason -- we are talking about 1) migratory and
dispersal flight at night and 2) night flight as a regular local activity.
We need to remember that butterflies don't just fly because they like it.
Their flight is related to species function - like mate location/mating,
feeding (nectar, dung, sap, etc.), escape from predators, mobility to
warmer spots for basking, etc.  In other words they need a stimulus (cause
and effect) to fly _any_ time.

Ron



 
 ------------------------------------------------------------ 

   For subscription and related information about LEPS-L visit:

   http://www.peabody.yale.edu/other/lepsl