Further contributions from Cook and Sargent
Cook (2); Sargent(2)
Laurence Cook's 1st reply to Ted Sargent (8/11/04):
Well, there are cases like that. Larval papilionids sometimes respond with different colours on different substrates. Where is the evidence that this has any relevance to the peppered moth?
L. M. Cook
Sargent's 2nd reply to Cook (8/12/04):
I will try to write a more complete response in a little while.
For now, I would simply say that this is an alternative hypothesis (to the so-called "classical" hypothesis); and, as such, might stimulate re-examination of some past data, and suggest some new observations and experiments designed to falsify it (and/or the "classical" hypothesis). I think this alternate hypothesis better fits some of the data we have (e.g., the speed with which melanics may appear, and the short time frame within which the frequency of the melanic form may increase or decrease - sometimes to essentially dominate a population, and then just as quickly essentially disappear). I find it difficult to attribute these changes entirely to selective predation by birds on the adult moths. We need more information on bird predation, and its place among the many mortality factors that affect the moth populations in question. I also think that the incidence of so-called "rural" melanism, especially in North America, should be more rigorously examined, partly in light of my "alternative" hypothesis.
Finally, I would point to my data on Panthea furcilla (now P. palescens) that was reported in the Texas A&M University symposium publication, "Adaptive Coloration in Invertebrates" (1990). There I found an effect on adult phenotype (namely, an increase in the frequency of melanics) when the larvae were fed on the "young," as opposed to the "old," needles of white pine. The sample was small, but the experiment (or similar ones) should be repeated.