Birdwing butterflies are named due to its large angular wings and birdlike flight. In the instance of the Wallace’s Golden Birdwing, the male wingspan can reach 150 mm and the female 190 mm.  The females are mostly brown with white markings on the forewings and yellow marks on the hindwing, the same can be observed on the underside. Whereas, the male forewings are black with an orange/red streak with a black odour-spot (used to attract females). The hindwing is orange with large golden spots with smaller gold and black spots. Underneath the male forewings are black with pale green spots and the hindwings are yellow and black, with black spots on the outer edge. It was the male’s vivid colour that first attracted Alfred Wallace.

Wallace Golden Birdwing Butterfly (1 and 2 are males, 3 and 4 are females) by Robert Henry Fernando Rippon licenced under CC-BY 2.0

Discovery

On the Bacan Island, Indonesia, in 1859, Wallace discovered this species. Within his book ‘The Malay Archipelago’ he described the female as being ‘immense’. He distinguished it as a Birdwing Butterfly. Therefore, he knew the male would be colourful. Eventually he caught one, writing:

“On taking it out of my net and opening the glorious wings, my heart began to beat violently, the blood rushed to my head…I had a headache the rest of the day, so great was the excitement produced by what will appear to most people a very inadequate cause.”

In 1865, Wallace wrote ‘On the phenomena of variation and geographical distribution as illustrated by the Papilionidae of the Malayan region’. Here he used the 37 butterflies of the Papilionidae family to describe evolution through islandisation. Thus, ensuing the Wallace’s Golden Birdwing Butterfly became one of Wallace’s most known discoveries.

Warning Colour

Aposematism is a theory by Wallace in 1867. He wrote it in response to a letter from Charles Darwin. In the letter Darwin enquires “why are caterpillars sometimes so beautifully and artistically coloured?”. Darwin was perplexed. Caterpillars are not sexually active so wouldn’t need bright colours. Aposematism hypothesis instead proposes that bright colours can be used to indicate that the animal is dangerous so should not be pestered or consumed. For example, the Wasp (Vespa) has black and yellow stripes warning of its sting. Birdwing butterflies’ caterpillars, including the Golden Birdwing, feed on Aristolochia plants. However, the poisons do not affect the caterpillar. Instead, the caterpillars are now toxic to predators. The red tipped spines of Wallace’s Golden Birdwing caterpillar indicate it is poisonous, so must be avoided.

Threats

Wallace’s Golden Birdwing Butterfly resides in highly productive wet lowland forests. It is a prime area for logging and plantations of crops such as coconut and nutmeg. Deforestation results in a decline of plants such as Aristolochia, required by the butterfly to feed and reproduce. Also, this butterfly features in commercial export of dead specimens for collections, decorations and live individuals for butterfly houses. The species go for high prices due to demand and low reproductive rates. Banned since 1987, wild-caught specimens can no longer be traded, but there are captive breeding programmes. Most consider these to be both sustainable and economically viable. However, conservationists disagree due to the lack of monitoring of exported butterflies, since it’s unknown whether they are from wild or captive origins.