text: chrysiridia rhipheus chrysiridia rhipheus ( madagascan sunset moth ) is a day - flying moth of the family . it is considered one of the most impressive and appealing - looking lepidopterans . famous worldwide , it is featured in most coffee table books on lepidoptera and is much sought after by collectors . it is very colourful , though the iridescent parts of the wings do not have pigment ; rather the colours originate from optical interference . adults have a wingspan of 7 – 9 cm ( 2 . 8 – 3 . 5 in ) . dru drury , who described the moth in 1773 , placed it in the genus papilio , considering it a butterfly . jacob hübner placed it in the moth genus chrysiridia in 1823 . later led to junior synonyms such as chrysiridia madagascariensis ( lesson , 1831 ) . at first the moth was thought to be from china or bengal , but was later found to be endemic to madagascar . it is found throughout the year in most parts of the island , with peak populations between march and august , and smallest numbers between october and december . females lay about 80 eggs under the leaves of omphalea spp . the caterpillars are whitish - yellow with black spots and red feet and are covered in club - ended black setae . silk spun from the mouth helps the caterpillars hold on to smooth leaves and climb back to the plant when they fall . after completing four instars , the caterpillars spin an open network cocoon . the pupal stage lasts from 17 to 23 days . chrysiridia rhipheus is the sole specialist herbivore of the four species of omphalea in madagascar . omphalea is toxic : the toxins are sequestered by the feeding caterpillar and retained in the pupal and adult stages . thousands of these moths migrate between the eastern and western ranges of their host plants . taxonomy the madagascan sunset moth was first described by the british entomologist dru drury in 1773 from a specimen obtained from a captain may of hammersmith . because of its resemblance to swallowtail butterflies , drury described the species as papilio the specimen drury received had the head of a different species attached , probably that of a butterfly , which had clubbed antennae — this trait is frequently used to differentiate moths from butterflies . once the inaccuracy in drury 's specimen was found , the moth was placed in the genus urania , until 1823 when the german entomologist jacob hübner placed it in a new genus , chrysiridia . the moth has also been described under other names . because drury described his specimen as having clubbed antennae and being tailless , william swainson thought it was a different species than the complete specimen described by cramer . in 1833 , swainson named the butterfly and the moth orientalis . other synonyms include u. by maassen in 1879 and u. var. madagascariensis by lesson in 1831 . native malagasy people call it or , from for " spirit " or " butterfly " and andriana for " noble " or " king " , therefore meaning " noble butterfly " , " noble spirit " , " king butterfly " or " king spirit " . the genus chrysiridia is entirely african and the only other species in the genus is the east african c. . chrysiridia is one of three diurnal genera . the other two genera are urania , its sister taxon , and alcides , the most basal . in the group , the use of is an ancestral state ( a ) . the more basal alcides feed on and omphalea , while urania and chrysiridia feed only on omphalea . description chrysiridia rhipheus has a wingspan of 7 – 9 centimetres ( 2 . 8 – 3 . 5 in ) , and sometimes up to 11 centimetres ( 4 . 3 in ) . moths from the highlands , 900 – 1 , 080 metres ( 2 , 950 – 3 , 540 ft ) , have a median wingspan of 7 cm ( 2 . 8 in ) ; moths from lower altitudes , 600 m ( 2 , 000 ft ) , have a median wingspan of 9 cm ( 3 . 5 in ) . like many other moths , the sunset moth has an uncanny resemblance to swallowtail butterflies , especially in its tails and colourful wings , and can easily be mistaken for a butterfly . the sunset moth is black with iridescent red , blue and green markings . there is a fringe of white scales on the wing edges , wider on the hindwings . the moth has six tails , very often lost or damaged during its life . pattern variations are common , and the moth is often partly asymmetrical ; one of the factors causing this is temperature shock during the pupal stage . wing microstructure unlike in many other moths , the colour of c. rhipheus 's wings does not come from pigments . the colour originates from coherent scattering and interference of light by the microstructure of the ribbon - like scales covering the moth 's wings . these structural characteristics make this species and its neotropical relative urania common subjects of research in optical science . the colours on the madagascan sunset moth 's wings are produced by the conjunction of two optical phenomena : an air - cuticle multilayer in the scales creates optical interference . each scale contains cuticle layers with randomly located blocks of cuticle that hold them in place and maintain an air gap between them . the layers and air gaps are narrower than the wavelength of visible light . the structure varies from one layer at the proximal end of each scale , to about six layers at the distal end . this multilayer structure strongly reflects certain wavelengths of light , which are determined by the thicknesses of the layers and the angle at which the light hits the scale . the scales are highly curved , which creates inter - scale reflection . this mechanism is unusual among lepidoptera . the proximal part of each scale is almost flat ; the scale then gradually curves up and then steeply bends down at the distal end , covering the proximal part of the next row of scales . because of this shape , adjacent rows of scales have valley - like grooves between them . this allows light to strike one scale , reflect at a roughly 90 ° angle , strike the next scale , and be reflected away from the wing . because the angle of each reflection is far from normal incidence , the interference effect favours reflection of different colours of light than are seen when light strikes near the top of the curved part of the scale . the colour seen in each part of the wing is the combination of the colours reflected by these two effects . because the cuticle layers are arranged in rows , with a cylindrical curve , the amount of the second type of reflection is dependent on the polarization of the incoming light . this makes the moth 's overall colour polarization - dependent . many insects can detect polarization of light , so it has been proposed that this feature may be used as a visual signal between moths . this has not yet been studied , however . distribution and habitat drury 's specimen was given to him by captain may of hammersmith and believed to have come from china . cramer believed the specimen came from chandernagore in bengal , however , giving rise to the french name " page de " . it is now known that chrysiridia rhipheus is endemic to madagascar . thousands of adult moths seasonally migrate between geographically isolated populations of their host plant omphalea spp . they can be found almost everywhere on the island , except in the south - west and the extreme south of the where their host plant is absent . they migrate from the three species in the dry deciduous forest in the west ( o. ankaranensis , o. occidentalis and o. palmata ) to the eastern rainforest species ( o. oppositifolia ) . the western species are largely in protected areas . the eastern species , on the other hand , is mostly unprotected and dispersed in widely scattered populations threatened by deforestation . being the only evergreen species , o. oppositifolia is probably crucial for the moth 's survival . the jamaican moth urania , from the same subfamily ( ) , most likely became extinct after the loss of one of its host plant species . the moths migrate in response to changes in the host plants . chrysiridia larvae defoliate the whole plant , and even eat the flowers and fruit , and thus have a considerable negative impact on the reproduction and survival of seedlings . the plants probably react by changing their nutrient and secondary compound levels , becoming toxic to the larvae and causing high mortality . omphalea populations that are not damaged by moths for long periods of time have lower toxicity . these factors cause mass increases in local population , followed by sudden crashes . the population crashes might result from increased larval mortality , but are more likely caused by the emigration of the adult moths . through semiochemicals , the plant may recruit hymenopteran parasitoids as a protection , hence playing a role in the population dynamics of the moth . host plants like c. and species of the genus urania , c. rhipheus is a specialist species whose caterpillars feed strictly on species of the pantropical genus omphalea ( euphorbiaceae ) . four species of the genus omphalea are endemic to madagascar : o. ankaranensis , a shrub from the limestone karst of northern madagascar o. palmata , a dry forest shrub , closely related to o. ankaranensis , but from western madagascar o. occidentalis , also a dry forest species of western madagascar o. oppositifolia , a tree from the east coast rainforest of madagascar omphalea , like many other members of the euphorbiaceae , possesses leaf nectaries that attract wasps , which are predators of early instar caterpillars . the leaf nectaries also attract ants . the ants usually protect their host plant , eating both the nectar and plant - eating insects on it . however , they generally completely ignore chrysiridia caterpillars , making it likely that the caterpillars possess a chemical deterrent as a primary defence . this chemical deterrent comes from the host plants . omphalea species contain alkaloids potentially sequestered or excreted by the caterpillar , the pupa and the adult moth . behaviour unlike most moths , the sunset moth is day flying and the bright aposematic colours warn predators of its toxicity , a strategy seen in many diurnal moths . another habit the moth has in common with many butterflies is the night resting posture — the wings are held vertically over the back . during their migrations they roost in a group for the night . the moth flies over the crown of trees and in clearings . sometimes because of high winds it is carried about 100 m ( 300 ft ) , it then falls , inert and wings closed , to the ground . life cycle continuous generations of the moth are present all year . the highest populations are found from march to august ( fall and winter ) , while the lowest are from october to december ( spring ) . the females lay their eggs late in the afternoon or at nightfall , and locate potential oviposition sites visually . like the eggs of other , the sunset moth 's eggs are domed with projecting ribs . a single egg weighs about 1 milligram ( 3 . 5 × 10 − 5 oz ) and usually has 17 ribs , but sometimes 18 or less often 16 . the eggs are usually laid on the lower surface of omphalea leaves , but occasionally on the upper surface . eggs are laid in groups of 60 to 110 , usually about 80 . after they hatch , the small caterpillars only eat the tissue ( parenchyma ) between the veins of the leaves . they do this to avoid the sticky and toxic latex produced by the plant 's and transported in the veins . after 3 – 4 days , the caterpillars also eat flowers , fruit , tendrils , petioles and young stems ( as well as continuing to eat leaves ) , defoliating the entire plant . they are particularly fond of the glands at the base of the leaf , near the petiole . they can deal with the chemical defences in the latex , which does not cause the problem of mouthpart coagulation . the caterpillars spin silk from their mouth with an ' ∞ ' motion of the head as they walk , this keeps them from falling from the smooth surface of the leaves . the silk also permits them to climb back to the plant should they fall . strong rain makes them fall despite the silk . there are four instars , and the caterpillar stage lasts from two months in the warm season to two and a half to three months in the cold season . the caterpillar is whitish - yellow with black spots and red feet and is covered in club - ended black setae . it has five pairs of prolegs on segments 3 to 6 and 10 , and six true legs attached to the thorax . after completing all but its last moult , the caterpillar spins a cocoon out of silk . the cocoon can be in the tree crown or between two leaves , but is most often near the ground , between moss and bark . it is an open network cocoon with large and irregular mesh . in the warm season , the cocoon takes about 10 hours to spin , the metamorphosis takes place about 29 hours later and lasts about 6 minutes . these durations are slightly longer in the cold season . the chrysalis stage lasts 17 days in november , the warmest month , and 23 days in july , the coldest month . five to six days before eclosion , the motifs of the wings start to become visible . the moth emerges during the night or in low light , by splitting the pupal case from the top . once out of the pupal exuvia ( the pupal exoskeleton ) , the moth finds a horizontal surface , from which it suspends itself by its four anterior legs . the wings are deployed in about 10 minutes , by pumping haemolymph into the wing veins . the moth then beats them a few times , waits 45 minutes to let them harden , then beats them lightly again . the moth finally takes flight between one and a half to two hours later . nectar sources adult moths prefer white or whitish - yellow flowers as a nectar source , which indicates that visual cues play a large role in their selection . most flowers visited are inflorescences of small flowers or have dense filaments , giving them the appearance of a bottle brush , often because of the conspicuous projecting stamens as in many leguminosae ( , myrtaceae and ) . however , not all white flowers elicit a response : the white and showy flowers of omphalea oppositifolia are not visited by the adult moths . nectar sources include the flowers of : terminalia ( indian almond ) camellia sinensis ( tea plant ) japonica ( ) eucalyptus spp . , especially e. saligna indica ( common mango tree ) all these flowers are white , with the exception of camellia sinensis which has a yellow centre , and all either have dense filaments or are formed of tight clusters of small flowers . in culture this spectacular moth is considered one of the most impressive and beautiful lepidoptera , rivalling almost any of the butterflies in brilliance of colouring and form . it is featured in most coffee table books on the lepidoptera , and is much sought after by collectors . it is collected in the wild , and raised commercially for the international butterfly trade ; its wings were used to make jewellery in the victorian era . the madagascan sunset moth appeared on a 6 postage stamp in the lesotho postal services butterflies of africa issue of 20 august 2007 . only one of the four species of host plants , omphalea oppositifolia , is used to raise the moth commercially , mainly using plants collected in the wild , but also some cultivated for the purpose . in malagasy , is polysemous for " butterfly " or " moth " and " soul " , there is little doubt that this is because a pupa resembles a covered corpse and that the adult emerges from it — like the soul from body of the dead . the malagasy people believe the soul of the dead or of ancestors appears in the form of a lepidopteran , and thus to attack it is to attack the ancestors .