NABOKV-L post 0006773, Tue, 10 Sep 2002 10:27:13 -0700

----- Original Message -----
From: Dieter E. Zimmer
To: Vladimir Nabokov Forum
Sent: Tuesday, September 10, 2002 12:08 AM
Subject: Re: Victoria Alexander: A nice example of non-utilitarian "mimicry"


Dr. Alexander does not seem to be aware than one of the very few examples of mimicry Nabokov gave is exactly "the cunning butterfly in the Brazilian forest which imitates the whir of a local bird" ("The Gift", p.110). I have gone through dozens of book shelves without finding the merest indication that there actually is such a case and what it might be. So I finally decided that Nabokov was referring to a picture in a wonderful book he knew thoroughly, "The Naturalist on the River Amazons" (2nd ed. 1864) by William Henry Bates, the godfather of Batesian mimicry, and I have reproduced it in my "Guide to Nabokov's Butterflies 2001." It shows a bird and a moth of about the same size hovering in front of a bunch of corollas, obviously intent on their nectar. The moth is the White-banded Day-sphinx (_Aellopos titan_ CRAMER, 1777, family Sphingidae, subfamily Macroglossinae).


This is what Bates wrote about it: "This moth is somewhat smaller than humming-birds generally are; but its manner of flight, and the way it poises itself before a flower whilst probing it with its proboscis, are precisely like the same actions of humming-birds [...] This resemblance has attracted the notice of the natives, all of whom, even educated whites, firmly believe that one is transmutable into the other. [...] But, of course, all these points of resemblance are merely superficial [...] there being no indication that the one having adapted in outward appearance with reference to the other." (Bates 1864: 115)

And that's exactly the point. Mimicry is when one animal adapts in outward appearance with reference to another. The normal natural selection explanation for such an adaptation is that it is advantageous, conferring the protection the model enjoys on the mimic.

Dr. Alexander does not quite call her case of a moth resembling a humming-bird mimicry, but she calls it "mimicry," performing a dizzying slalom: "... the clearwing hummingbird moth... seems to be attempting to mimic the appearance of the hummingbird with the clearwing innovation. This is a truly remarkable non-utilitarian resemblance, a coincidence, one that Nabokov would have appreciated. To my knowledge, no one has ever made the argument that the resemblance between the hummingbird and the hummingbird moth confers a reproductive advantage. The hummingbird moth is not a mimic of the hummingbird. Neither the moth nor the bird required the other as a model (for predators to recognize) on which to base its appearance. The resemblance between hummingbird and hummingbird moth is one that was created by natural selection, but which does not serve a purpose."

To set things straight, because Dr. Alexander has got it right but then immediately goes on to obfuscate her own insights: Both the moth and the bird were created by natural selection, including their outward appearance and their peculiar manner of hovering flight. Independently, evolution was pursuing the same purpose: to enable them to draw nectar (presumably giving them a reproductive advantage over moths and birds that exploited the nectar of flowers less well). It is an instance of convergent evolution and doesn't have anything to do with mimicry. If we extended the concept of mimicry to all resemblances we discover in nature, it would become utterly void and meaningless. The cat does not "seem to be attempting to mimic the appearance" of the dog just because it also has four legs. There are zillions of resemblances in nature, zillions of features produced by the Darwinian mechanism of mutation and selection, all optimized for specific purposes, and everyone is invited to appreciate and enjoy those he discovers. But arguing that actual mimicry does not necessarily serve a purpose, as Nabokov has done a couple of times and in which Dr. Alexander is supporting him, is something entirely different, and contrary to what she seems to think herself, she does not give the slightest evidence that it has ever happened.
Dieter E. Zimmer
Berlin, Sep 11, 2002 -- 8:30am

PS. Dr. Alexander's humming-bird moth has transparent wings, and she thinks this is an "innovation" and "a bit unusual for a moth." Well, what can I say without sounding inpolite? As any look into one of those pretty and useful field guides to butterflies and moths would have shown her, there is a whole (and large) family of clear-wing moths (Sesiidae). There also is a large bunch of clearwinged hawkmoths (Sphingidae). The biggest one in North America probably is _Hemaris thysbe_ FABRICIUS, 1775. You may have a look at it at www.silkmoths.bizland.com/shthysbe.htm. I can't help believing that a certain basic knowledge of a field of nature is useful if you want to embark on some of its most difficult questions.