The Magellan Birdwing (Troides magellanus) is a large and striking Birdwing

Birdwing

Birdwings are papilionid butterflies native to the Indian Subcontinent, mainland and archipelagic Southeast Asia and Australasia, and are usually regarded as belonging to three genera: Ornithoptera, Trogonoptera and Troides. Some authorities include additional genera...

 butterfly

Butterfly

A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured...

 found in the Philippines

Philippines

The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...

 and on Taiwan

Taiwan

Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...

's Orchid Island

Orchid Island

Orchid Island is a 45-km² volcanic island off the southeastern coast of Taiwan island and separated from the Batanes of the Philippines by the Bashi Channel of the Luzon Strait. It is governed as Lanyu Township of Taitung County...

.

This butterfly is named for the explorer Ferdinand Magellan

Ferdinand Magellan

Ferdinand Magellan was a Portuguese explorer. He was born in Sabrosa, in northern Portugal, and served King Charles I of Spain in search of a westward route to the "Spice Islands" ....

 who was killed in the Philippines in 1521.

Description

T. magellanus shows a blue-green sheen if viewed from an oblique angle.
Troides magellanus and the much rarer T. prattorum, are noted for their use of limited-view iridescence

Iridescence

Iridescence is generally known as the property of certain surfaces which appear to change color as the angle of view or the angle of illumination changes...

: the yellow of the dorsal hindwings is modified by bright blue-green iridescence which is only seen when the butterfly is viewed at a narrow, oblique angle. This "grazing iridescence" is brought about through diffraction

Diffraction

Diffraction refers to various phenomena which occur when a wave encounters an obstacle. Italian scientist Francesco Maria Grimaldi coined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1665...

 of light

Light

Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...

 (after back-reflection) by the wings' extremely steeply-set, multilayered rib-like scale

Scale (zoology)

In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...

s (rather than the ridge-lamellae of most other iridescent butterflies, such as Morpho

Morpho (butterfly)

A Morpho butterfly may be one of over 80 species of butterflies in the genus Morpho. They are Neotropical butterflies found mostly in South America as well as Mexico and Central America. Morphos range in wingspan from the 7.5 cm M. rhodopteron to the imposing 20 cm Sunset Morpho, M....

species). Such limited-view iridescence was previously only known from one other species, the lycaenid

Lycaenidae

The Lycaenidae are the second-largest family of butterflies, with about 6000 species worldwide, whose members are also called gossamer-winged butterflies...

 Ancyluris meliboeus

Ancyluris meliboeus

The Meliboeus Swordtail is a butterfly of the Riodinidae family. It is found in Surinam, Brazil, Colombia, Bolivia and Peru....

. In A. meliboeus, however, the iridescence is produced by ridge-lamellar scales and features a wider range of colours.