As Boyd notes in Vladimir Nabokov: The American Years, "He could not accept that the undirected randomness of natural selection would ever explain the elaborateness of nature's designs, especially in the most complex cases of mimicry where the design appears to exceed any predator’s powers of apprehension."
Boyd summarized the artist's scientific bona fides in an appreciation in Natural History.

For most of the 1940s, he served as de facto curator of lepidoptera at Harvard University’s Museum of Comparative Zoology, and became the authority on the little-studied blue butterflies (Polyommatini) of North and South America. He was also a pioneer in the study of butterflies' microscopic anatomy, distinguishing otherwise almost identical blues by differences in their genital parts.

Later employed at Harvard as a research fellow in entomology while teaching comp lit at Wellesley, Nabokov published scientific journal articles in The Entomologist, The Bulletin of the Museum of Comparative Zoology, The Lepidopterists' News, and Psyche: A Journal of Entomology.

According to Boyd, Nabokov wrote "a major article," subsequently lost, "with 'furious refutations of "natural selection" and "the struggle for life."'" He completed the paper in 1941 but all that survives is a fragment in his memoir, Speak, Memory:

The mysteries of mimicry had a special attraction for me. Its phenomena showed an artistic perfection usually associated with man-wrought things. Consider the imitation of oozing poison by bubblelike macules on a wing (complete with pseudo-refraction) or by glossy yellow knobs on a chrysalis ("Don’t eat me--I have already been squashed, sampled and rejected"). Consider the tricks of an acrobatic caterpillar (of the Lobster Moth) which in infancy looks like bird's dung, but after molting develops scrabbly hymenopteroid appendages and baroque characteristics, allowing the extraordinary fellow to play two parts at once (like the actor in Oriental shows who becomes a pair of intertwisted wrestlers): that of a writhing larva and that of a big ant seemingly harrowing it. When a certain moth resembles a certain wasp in shape and color, it also walks and moves its antennae in a waspish, unmothlike manner. When a butterfly has to look like a leaf, not only are all the details of a leaf beautifully rendered but markings mimicking grub-bored holes are generously thrown in. "Natural Selection," in the Darwinian sense, could not explain the miraculous coincidence of imitative aspect and imitative behavior, nor could one appeal to the theory of "the struggle for life" when a protective device was carried to a point of mimetic subtlety, exuberance, and luxury far in excess of a predator's power of appreciation. I discovered in nature the nonutilitarian delights that I sought in art. Both were a form of magic, both were a game of intricate enchantment and deception.

Sounds like…intelligent design?

That’s what Amardeep Singh thought. He teaches literature at the same university (Lehigh) where Darwin-doubter Michael Behe has been made to feel very unwelcome. Singh comments in a blog entry that his students are startled to read the passage from Speak, Memory. I bet.

My students, I was happy to see, were a little shocked that someone with Nabokov's way of seeing things would say something that might even remotely be construed as Intelligent Design-ish. And indeed, Darwinian natural selection, as I understand it, does have a fine explanation for the "miraculous coincidence of imitative aspect and imitative behavior": any mutant variety that doesn't exhibit a perfect imitation is going to get eaten. And if you have enough random-pattern butterflies getting eaten over time, eventually a strain that has a slightly better design is going to come around and not get eaten.

Comforting! But Singh misses the point of Nabokov's question. It's not the perfection of the pattern that needs an explanation. The novelist/lepidopterist asked, if a particular artistic subtlety in that perfection is beyond the ability of a predator to perceive, how did nature select it?