Re: My last word

Brian D Harper (
Wed, 21 Apr 1999 14:03:19 -0700

At 10:20 AM 4/20/99 EDT, Kevin wrote:

>In a message dated 4/20/99 12:14:26 AM Mountain Daylight Time,
> writes:
>> Thanks for your considerate reply. It was exactly the kind of
>> response I was hoping for. My post was not intended to be an
>> endorsement of Wells but rather it was kind of a knee jerk
>> reaction against the approach to debate that seems to be favored
>> by some. Wells made some specific allegations that can be dealt
>> with specifically. Instead, some seem to want to take the track
>> that Wells has no right to raise these objections since his
>> robes are not long enough and his hood is of the wrong color.
>> This I find enormously irritating and contrary to the spirit of
>> science.
>To my knowledge, no one said that Wells did not have the RIGHT to raise
>objections. What we were saying is that his lack of knowledge of the
>peppered moth and his lack of experience in biological field work (and
>apparantly in scientific research in general), not to mention his more
>political ambitions, has led him to make foolish accussations that he cannot
>support, yet stubbornly clings to even after more knowledgeable and
>experienced people have explained how and why he is wrong. We do not object
>to Wells because he has the wrong credentials; we object to Wells because he
>is a fool.

How nice for you. I have no expertise in industrial melanism,
biological field work etc. I do know something, however, about
experimental methods. Nothing Wells has said in this regard
strikes me as foolish. In fact, quite the opposite.

BTW, I take it you are an expert in this field?

[skipping some]

>> What occurred to me originally was that a photograph of a moth
>> sitting on an exposed tree trunk will reinforce not only the
>> idea of increased visibility due to coloration but also increased
>> visibility due to being out in the open on an exposed tree trunk.

>If you did not already know that the moths were resting on tree trunks, how
>could you distinguish that from say a large diameter bough? The point is
>still, though, that the PLACE mattered little, only the color contrast.

Interesting. Below you give differences in hunting styles which
show that the place does matter. Of course, this would matter
little wrt the central claim that bird predation is the cause
for the differential success of the two colorations. Nevertheless,
it is an indication that place *might* matter. Has anyone demonstrated
empirically that selective predation occurs where moths normally
rest? As another possible influence of location, would you happen to
know off hand whether lichens grow better on tree trunks as opposed
to branches?

The brief quote I gave from Futuyma indicated that viability
of the two forms differs even in the absence of predation.
This suggests to me that it might be important to figure
out what the mechanism for this is (perhaps someone already
has) and then to check whether air pollution might have some
effect on this mechanism.

>> Perhaps I'm feeble minded, but being in an exposed position
>> seems to accentuate the importance of coloration and to accentuate
>> the hypothesis that such coloration affects bird predation. One gets
>> a ready minds eye picture of how easy it would be for a bird to
>> swoop in and nail that sitting duck :).
>That's part of the reason why the situation is more complicated than Wells
>(or the standard high school textbook description) make it out to be.
>However, there are bird species -- nuthatches, titmouses, chickadees, small
>woodpeckers and the like -- who actually hunt insects by crawling around the
>upper trunks and smaller branches up inside the canopy. As such, these birds
>would be the most likely predators rather than say blue jays that hunt "on
>the wing" so to speak, and while they would be closer to their prey, a well
>camouflaged moth that remains still would be overlooked, whereas one whose
>body color was a sharp contrast to the background would be attacked even if
>it did not move. These small "creeper" birds hunt by movement and color
>contrast, not by pattern recognition.

Which brings me back to one of my questions above. Is there
empirical evidence for differential predation in an environment
such as you describe above?

Please accept my humblest apologies if I am acting overly
foolish :).

Brian Harper
Associate Professor
Applied Mechanics
The Ohio State University

"All kinds of private metaphysics and theology have
grown like weeds in the garden of thermodynamics"
-- E. H. Hiebert