THE CRYPTIC MOTH
Until recently the great majority of naturalists
believed that the species were immutable
productions, and had been separately created.
-- Charles Darwin, The Origin of Species
England's amateur naturalists of the nineteenth century formed a large and dedicated fraternity. Still, not one of them so much as suspected that a recently documented change in the color of an insect was a sign that the world, together with its climate, was being forever altered. Among the fraternity's more avid members was the lepidopterist R. S. Edleston, whose well-documented observations on butterflies and moths occasionally made their way into the pages of such scientific journals as Entomologist and Zoologist. Yet each time the bespectacled Edleston peered into the glass-covered case on his wall, he was haunted by the same recurring question: What strange alchemy had given rise to the pinioned and mute creature before him?
Edleston lived about a mile from the center of Manchester, whose population had risen from some 10,000 early in the eighteenth century to 300,000 by 1848, when the collector's story began to unfold. He had already gathered and carefully preserved many of England's estimated 780 species of larger moths, and he knew their major characteristics well. In contrast to butterflies, which are active during the daylight hours, moths emerge at twilight and retire before sunrise, a trait