In grad school, I read and learned from Ernst Mayr’s Populations, Species, and Evolution (1963, 1970, Harvard University Press). I think that “Alarming butterflies and go-getter fish” extremely simplifies Mayr’s position on speciation. The article says that Mayr focuses solely on geographic separation, “allopathic speciation.” This ignores the fact that Mayr discussed a variety of other isolating mechanisms besides allopathic speciation. The article also discusses possible genetic differences between populations of R. pomonella but offers no evidence that those allegedly different genetic populations are incapable of interbreeding. Thomas W. Kavanagh
Indiana University
Bloomington, Ind.

I noticed in “Alarming butterflies and go-getter fish” an example of an oft-repeated misinterpretation of the theory of evolution. The article states that some butterflies “happened upon” color variations that resembled the older species. Evolution works negatively rather than positively: Those ancestors that didn’t exhibit the color variation were more likely to be killed by predators and less likely to produce offspring. The butterflies that exhibited color variations did not happen upon them as if they went shopping for new clothes. They manifested a mutation that happened to give them a survival advantage. They had no choice in the matter. Chip Wolfe
Austin, Texas