Wallace's Golden Birdwing (Ornithoptera croesus)

In this guide

1. Description and identification
2. Life cycle: egg, caterpillar, chrysalis and adult
3. Where Wallace's golden birdwing lives
4. Host plants and diet
5. Behavior: flight, courtship and daily routine
6. Similar butterflies and how to tell them apart
7. Quick facts
8. Did you know?
9. Frequently asked questions

Description and identification

Wallace's golden birdwing is one of the birdwings, the giant tropical members of the tribe Troidini within the swallowtail family, Papilionidae. Despite the family name it has no tails: birdwings have long, narrow, angular forewings and a rounded hindwing, and their slow, gliding, powerful flight is the reason for the name. Alfred Russel Wallace described the species in 1859 from a specimen he took on the island of Bacan, and it remains restricted to a small group of islands in eastern Indonesia.

Adult butterfly

• Wingspan: about 5–7.5 in (13–19 cm). Males sit at the lower end of that range and females at the upper, and a large female is one of the biggest butterflies in Asia.
• Male upperside: the forewing is velvety black with a broad wedge of metallic orange-gold along the leading edge, and a long black scent fold, the androconial fold, runs down the inner margin. The hindwing is orange to golden-red, crossed by black veins, with a black outer border enclosing a chain of small golden and black spots. The gold is partly structural, so it shifts between orange, brass and green-gold with the angle of view.
• Male underside: the forewing is black with a scatter of green-gold patches; the hindwing is deep gold with heavy black veins and a row of black submarginal spots.
• Female: considerably larger and quite different. The ground colour is dark brown to blackish-brown, with a series of small white to cream spots on the forewing and a row of large pale yellow blocks, often with dark centres, across the hindwing. The underside is a faded copy of the upperside.
• Body: black thorax with a bright red patch of hair on the underside, typical of the pipevine-feeding Troidini, and a yellow or cream abdomen.

How to identify a Wallace's golden birdwing

Geography does most of the work: this is the only golden birdwing in North Maluku. A huge butterfly gliding slowly along the forest canopy on Halmahera, Bacan, Ternate, Tidore or Morotai, black with a burning orange-gold hindwing, is a male Wallace's golden birdwing. The green-and-black common green birdwing shares parts of the region but is emerald rather than gold, and the yellow-and-black goliath birdwing belongs to New Guinea and its satellites. Females are harder: look for the size, the red hair on the underside of the thorax and the row of large pale hindwing blocks.

Life cycle: egg, caterpillar, chrysalis and adult

Much of the early biology of this butterfly is still poorly documented in the wild, and the account below combines what has been recorded for Ornithoptera croesus with the well-established pattern shared by every birdwing. In the lowland tropics the species breeds through the year, and the cycle from egg to adult takes roughly two to three months.

Eggs

The female lays her eggs singly on or beside the leaves of a pipevine, usually on the underside of a leaf or on a tendril of new growth. Birdwing eggs are among the largest laid by any butterfly, roughly 2–3 mm across, spherical to slightly flattened, and golden-yellow to orange, coated with a sticky secretion that glues them in place. A female inspects a vine carefully first, drumming the leaf with her forelegs, and lays few eggs on any one plant, because a single caterpillar can strip a small vine on its own.

Caterpillar

The caterpillar is dark brown to blackish-grey and thickly set with soft, fleshy, finger-like tubercles, usually with a pale cream or whitish saddle band across the middle of the body. Like all swallowtails it carries an osmeterium, a forked orange-red gland that everts from behind the head when the larva is disturbed and releases a sharp, unpleasant smell. It eats steadily, first the soft new leaves and later the tougher ones, and will chew the stem of the vine as well. The larva stores the aristolochic acids present in its food plant, which makes both the caterpillar and the adult butterfly distasteful to birds, and the warning is advertised by the red hair on the adult's thorax.

Chrysalis

The full-grown larva leaves the vine and pupates on a nearby stem or the underside of a leaf, held upright by a silk girdle around the middle with the tail fixed to a silk pad. The chrysalis is large, brown to golden-brown with darker markings and pale raised flanges, and looks convincingly like a curled dead leaf. The adult emerges after about four to six weeks, a long pupal stage even by tropical standards.

Adult butterfly

Newly emerged adults hang for an hour or more while the huge wings harden. Precise lifespan data for wild O. croesus is scarce, but birdwings in general live for several weeks and can reach around three months when nectar is plentiful, which is exceptionally long for a butterfly and allows a female to lay over a long period rather than all at once.

Where Wallace's golden birdwing lives

Wallace's golden birdwing is endemic to the northern Maluku islands, the Moluccas, in eastern Indonesia. It is recorded from Bacan, where Wallace first found it, and from Halmahera, Ternate, Tidore, Morotai and Kasiruta. That is the entire world range: a scatter of volcanic islands smaller in total than many single national parks. Around six subspecies are recognised, one or two to an island group, and they differ in the width and tone of the golden area; the form from Halmahera is the one most often illustrated and the most intensely golden.

The butterfly is a creature of wet lowland forest. It is most often seen in primary and old secondary rainforest below about 1,000 ft, along river valleys, in swamp forest and freshwater swamp margins, and at forest edges and clearings where flowering trees and climbing pipevines grow together. Males come out into sunlit gaps and along watercourses; females stay closer to cover, where the host vines are.

Habitat is the whole conservation problem. Lowland forest on Halmahera and Bacan has been cleared for logging, oil palm and, increasingly, large-scale nickel mining, and because the pipevine hosts are forest-interior climbers, the butterfly cannot follow onto plantation land. The IUCN lists Ornithoptera croesus as Endangered, all birdwings of this genus are on Appendix II of CITES, restricting international trade, and the species is protected under Indonesian law. Managed butterfly farming, in which villagers plant pipevines and rear larvae for a legal export quota, has been promoted as an alternative to wild collecting.

Host plants and diet

Caterpillar host plants. The larvae feed on pipevines of the family Aristolochiaceae, above all species of Pararistolochia and to a lesser extent Aristolochia. These woody climbers are loaded with aristolochic acids, compounds toxic to most herbivores; the birdwing caterpillars not only tolerate them but store them in their tissues and carry them through the chrysalis into the adult. It is the same chemical strategy used half a world away by the pipevine swallowtail of North America. The dependence is absolute: no pipevine, no birdwing, which is why forest clearance removes the butterfly even when flowers remain.

Adult diet. Adults drink flower nectar and need a great deal of it to power such a large body. They visit the flowers of forest trees, vines and shrubs, including hibiscus, Ixora, Mussaenda, Bauhinia and lantana at forest edges, feeding on the wing with the wings still beating rather than settling fully. Males also take moisture from damp ground and riverbanks. Adults do not feed on foliage or fruit in any significant way, and the long adult life depends on a continuous nectar supply.

Behavior: flight, courtship and daily routine

Flight. The flight is slow, deep and powerful, with long glides on flat wings between heavy wingbeats, and it looks far more like a bird than an insect. That deliberate, unhurried movement is characteristic of a toxic butterfly with little to fear, and it is the origin of the name birdwing. Males fly higher than females, patrolling along the canopy, ridge lines and river courses, and they descend to flowering trees and to sunlit gaps.

Daily rhythm. Activity is concentrated into the early morning and the late afternoon. Males are most often seen between about eight and eleven in the morning, feeding at flowers and patrolling; through the hottest hours both sexes rest in the shade of the canopy, and there is a second burst of activity before dusk. In heavy rain the butterflies shelter under large leaves and do not fly at all.

Courtship. A male that meets a female hovers above and slightly behind her, beating his wings rapidly and fanning scent from the androconial fold along the inner margin of his forewing over her antennae. A receptive female settles and lowers her wings; an unwilling one flies steeply upward or drops into cover. Mating can last several hours and the pair is vulnerable throughout. The general sequence is set out in our guide to how butterflies mate and reproduce.

Sexual dimorphism and why it exists. The difference between the sexes is among the most extreme in the butterfly world. The male advertises: his gold is a signal to females and a warning to predators, and he can afford it because he spends his time in flight high in the open. The female must spend hours crawling over vines in the understorey searching for egg sites, and her brown and cream pattern breaks up her outline against dappled leaf litter and bark. The same logic separates the sexes of other birdwings, including Queen Alexandra's birdwing, the largest butterfly on Earth.

Similar butterflies and how to tell them apart

Quick facts

Did you know?

• In The Malay Archipelago (1869) Alfred Russel Wallace described catching the first specimen on Bacan and wrote that the sight set his heart beating violently, the blood rushed to his head, and he had a headache for the rest of the day. It is probably the most quoted passage ever written about catching a butterfly.
• Wallace named the species croesus after the fabulously rich king of Lydia, for the colour of the male's hindwing.
• The gold is not only pigment. Ridged scales on the male's hindwing scatter light so that the colour slides between orange, brass and green-gold as the butterfly turns, which is why photographs of the same individual can look like different insects.
• Birdwing eggs are the largest of any butterfly, up to about 3 mm across, and the caterpillar that hatches is big enough to eat a whole young pipevine leaf in its first day.
• Every member of the genus Ornithoptera is on CITES Appendix II, and the closely related Queen Alexandra's birdwing is on Appendix I, which means the birdwings are among the most tightly trade-regulated insects in the world.
• Village butterfly farms in Maluku and neighbouring provinces now rear birdwings on planted pipevines. Done properly this raises far more butterflies than it removes and gives local people a reason to keep the forest standing.

In summary

Wallace's golden birdwing, Ornithoptera croesus, is an Endangered swallowtail endemic to Bacan, Halmahera and neighbouring islands of North Maluku, Indonesia, where it lives in wet lowland rainforest. Males span about 13 cm and are black with a metallic orange-gold hindwing and a golden wedge on the forewing; females reach 19 cm and are dark brown with cream forewing spots and large pale yellow hindwing blocks. Females lay big golden eggs singly on pipevines, the dark tubercled caterpillar stores the plant's aristolochic acids and so is toxic, and the leaf-like chrysalis takes four to six weeks. The butterfly glides slowly along the canopy, feeds at forest flowers, and survives only where lowland forest and its host vines remain.

Frequently asked questions about the wallace's golden birdwing butterfly

What is Wallace's golden birdwing?

Wallace's golden birdwing, Ornithoptera croesus, is a very large swallowtail butterfly endemic to the northern Maluku islands of Indonesia. The male is black with a metallic orange-gold hindwing, the female is larger and brown with cream and yellow markings, and the caterpillars feed on poisonous pipevines. The IUCN lists the species as Endangered because its lowland rainforest is being cleared.

Where does Wallace's golden birdwing live?

It is found only in North Maluku in eastern Indonesia, on Bacan, Halmahera, Ternate, Tidore, Morotai and Kasiruta. Within those islands it keeps to wet lowland rainforest, swamp forest, river valleys and forest edges, mostly below about 1,000 feet, wherever climbing pipevines grow. Around six subspecies are recognised across that small range.

How can you tell the difference between male and female Wallace's golden birdwings?

Colour and size separate them at a glance. The male is black with a broad orange-gold wedge on the forewing and an orange to golden hindwing crossed by black veins. The female is considerably larger, dark brown to blackish, with small white spots on the forewing and a row of large pale yellow blocks on the hindwing.

What is the conservation status of Wallace's golden birdwing?

The IUCN Red List classifies Ornithoptera croesus as Endangered, meaning it faces a very high risk of extinction in the wild. All Ornithoptera birdwings are also listed on Appendix II of CITES, which regulates international trade, and the species is protected under Indonesian law. Logging, oil palm and nickel mining on Halmahera and Bacan are the main threats.

Who was Wallace's golden birdwing named after?

It honours Alfred Russel Wallace, the British naturalist who co-founded the theory of evolution by natural selection and who collected the first specimen on the island of Bacan in 1859. Wallace also chose the scientific name croesus, after the legendarily wealthy king of Lydia, because of the gold colour on the male's hindwing.

What does the caterpillar of a Wallace's golden birdwing look like?

The caterpillar is dark brown to blackish-grey, thickly covered with soft fleshy finger-like tubercles, and usually carries a pale cream saddle band across the middle of the body. Like all swallowtail larvae it can evert a forked orange-red gland called an osmeterium when threatened, releasing a strong smell. It feeds on pipevine leaves and stems.

How big is Wallace's golden birdwing?

The wingspan ranges from about 5 to 7.5 inches, or 13 to 19 centimetres. Males are at the smaller end and females at the larger, so a big female is among the biggest butterflies in Asia. Even so, it is smaller than Queen Alexandra's birdwing of Papua New Guinea, the largest butterfly in the world.

What do Wallace's golden birdwings eat?

The caterpillars feed only on pipevines, chiefly species of Pararistolochia and Aristolochia, whose aristolochic acids they store as a chemical defence. Adults drink flower nectar, visiting hibiscus, Ixora, Mussaenda and other forest trees, vines and shrubs, often feeding on the wing. Males also take mineral-rich moisture from damp ground and riverbanks.

Is Wallace's golden birdwing poisonous?

It is unpalatable to predators but harmless to people. The caterpillar stores aristolochic acids from its pipevine food plant and passes them on to the adult, so birds that try one learn to leave the species alone. The red hair on the underside of the adult's thorax advertises this. The butterfly cannot bite or sting.

Can you legally buy a Wallace's golden birdwing specimen?

Only under permit. The species is on Appendix II of CITES, so any international trade needs export and import documentation, and Indonesia protects it under national law with a limited quota system. Legally traded specimens come from registered butterfly farms that rear larvae on planted pipevines rather than from wild collecting.