Purple Emperor

Fascinating facts about the Purple Emperor

• A male’s wings shimmer with a purple-blue iridescence that only appears in the 70–80 mm wingspan of the smaller sexes, while the larger 80–92 mm females stay matte brown, showing how a tiny color trick can turn a modest butterfly into a forest jewel.
• Unlike most butterflies that sip nectar, these emperors sip honeydew, oak sap, and even the liquid from dung, urine, and road-kill, a diet that lets them thrive where flowers are scarce and reveals a hidden ecological role in recycling forest waste.
• Collectors once dangled a 4.5-metre (about 15-foot) high net from a pole to snare a male; males sometimes descend to feed on decaying carcasses.
• Larvae spend the winter curled in the forks of sallow branches, changing from green to brown to blend in, then pupate in a leaf-shaped chrysalis 30–35 mm long before the adults burst forth in July and linger into August, demonstrating a precise seasonal choreography tied to woodland cycles.
• Historical records show the butterfly vanished from much of southern England after World War I timber drives, and Heslop estimated that a viable colony needs at least 1,000 adults each year.

At a glance

About the Purple Emperor

The purple emperor, Apatura iris, drifts through the dense, mature oak woodlands of Europe with a regal air. Males flash a violet-blue iridescence across dark brown wings that bear delicate white bands, spots and a modest orange ring on each hindwing, while the slightly larger females (80–92 mm) display the same pattern without the sheen. Their larvae, green with yellow and white markings and crowned by two prominent anterior “horns,” hide along the midrib of sallow leaves, emerging at night to feed before hibernating in the forked branches where they turn brown to match the winter bark. In June the caterpillars spin a pale-green chrysalis that mimics a leaf shoot, and by July the adults take to the canopy, lingering above the treetops where females lay their eggs on broad-leaved sallow (Salix caprea) and related willows. Unlike most butterflies, the purple emperor shuns nectar, sipping instead on aphid honeydew, oak sap, and the occasional dung, urine or animal carcass, a habit that once lured collectors to set out decaying roadkill to draw males down. Males defend lofty territories, descending only to drink from puddles or to investigate the scent of a fresh kill, a behavior that sadly makes them vulnerable to traffic. Their life, a delicate balance of canopy flight, nocturnal larval feeding, and opportunistic scavenging, unfolds across the broad Palearctic, from southern Britain’s ancient woodlands to the forests of central and western China.

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