IN Jamaica the fifth instar larvae of the New World hawkmoth, Erinnyis ello, exhibit four basic colours: green, blue, green-grey and brown. The green, blue and green-grey larvae feed and rest on the leaves of their commonest food plant (Poinsettia pulcherrima). The brown larvae also feed on these leaves, but they rest for many hours during the day on the base of the trunk, sometimes several yards below where they feed1. All the larvae are preyed on during the day by wasps (Polistes crinitus) and to a very small extent by an anole (Anolis lineatopus). Because the wasps search for their prey only in the foliage of the Poinsettia bushes, the three forms staying constantly on its leaves suffer heavily from predation, as selection experiments in the wild have demonstrated1. By contrast, all the larvae which rest from time to time on the trunk of the food plant enjoy an almost complete freedom from predators.