Each of these butterflies, the fruit of two or three broods of this summer, had hatched successfully from one of those emerald cases that Teale's caterpillar had been about to form when the parasitic larvae snapped it limp, eating their way out of its side. They had hatched, many of them, just before a thunderstorm, when winds lifted the silver leaves of trees and birds sought the shelter of shrubbery, uttering cries.