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A new species of papilionid butterfly, officially named Papilio natewa, has been discovered on a Fijian island, bringing to three the total number of swallowtail butterflies known from the region.
This is such a remarkable butterfly that scientists are wondering how it has gone unnoticed for so long.
It is a relatively large insect, measuring some eight centimetres across. True to its name, the swallowtail butterfly has two elongated edges projecting from the hind wings, which trail as it flutters through the canopy of the forest in which the species was found.
It has striking black and white zigzags emblazoned on the top or its wings, and a cream and black speckled pattern underneath. All of this is gilded with soft yellows and blue eye spots.
John Tennent, a scientific associate at the Museum, says, 'The discovery of a new swallowtail in the Pacific is hard to believe.
'The new swallowtail is a big butterfly, recognizable from a distance. There were previously only two swallowtail butterflies known from the region, endemic to Fiji and Samoa. Both are large but dull in appearance.
'To find a third as large and colourful and unusual, with its long, sword-like tails really is remarkable.'
The butterfly was actually first found and photographed by the ornithologist Greg Kerr, who was working on the Natewa Peninsula on the Fijian island of Vanua Levu in 2017.
So striking was the butterfly that lepidopterists who first saw the photographs thought the images may have been faked. It didn't seem plausible that such an insect could have gone unnoticed all this time.
Not only that, but the butterfly simply did not fit with what was known about butterfly diversity on Fiji, or even in the wider region as a whole.
After confirming with Greg that not only were the photographs genuine but that the butterfly had been spotted on multiple occasions, the following year John and a colleague, Visheshni Chandra, arrived on Vanua Levu to see for themselves.
Initial sightings of the butterfly were sporadic, hindered by the fact that no one was quite sure of its habitat.
After a few months of field work, its true habitat was finally discovered. The insect was regularly spotted along a former logging track that was bounded by forest gardens and deep, undisturbed primary rainforest.
'It is a forest butterfly,' explains John, 'and although almost everyone in the camp was aware of its importance it was rarely seen, and then only fleetingly.
'I arrived in July 2018, but it was not until early August that I found its probable true habitat and was able to make observations on its behaviour, habitat and ecology.'
Within just a couple of days the researchers made multiple sightings and were able to collect several specimens. They named the new species Papilio natewa after the peninsula on which it was found.
'Most islands and island groups have been moderately well surveyed now,' explains John. 'Although there surely remain some new butterfly discoveries to be made, they are most likely to be in the very small and/or fast-flying butterfly groups.'
There is still much about P. natewa that remains a mystery, including almost everything about its natural history.
'The early stages of its life and even its host plant remain unknown,' says John. 'And figuring that out will be a big job for someone in the future.'
Even how the butterfly ended up on the island is not fully understood. The insect may be related to two other species of Papilio butterflies, P. demoleus and P. machaon, which have much wider distributions across much of Asia. Genetic analysis shows that the new species has some affinity to a third butterfly, P. anactus, found in eastern Australia.