IUCN Red List Conservation Status: Endangered
Ornithoptera croesus is a highly attractive birdwing butterfly with a unique golden-yellow coloration in the male. It is restricted, as two well-known subspecies and a little-known third, to a few islands in the Moluccas (Indonesia). It is at risk primarily because of deforestation but possibly also as a result of insecticidal spraying on a large scale. Conservation of O. croesus is inadequate and a thorough assessment of its status followed by protection of suitable habitat is needed.
Ornithoptera croesus has a wingspan of 130-150 mm in the male and 160-190 mm in the female (4). The male is dark brown, orange, and golden with a green and black lower surface. The female of the nominate subspecies is brown with white markings (1, 2, 3, 4, 6). The subspecies O. c. lydius, commonly seen in the butterfly trade, differs widely from the nominate subspecies described below. The female is unique among the birdwings in being a mimic of unpalatable Danainae species. A third subspecies, O. c. sananaensis is only known from a single female and is stated to be intermediate between the first two.
The male upper forewing ground colour is very dark brown with a broad iridescent orange radial band and short anal streak (1, 2, 4, 8). The upper hindwing is orange with a narrow black margin and a golden-yellow subcostal patch, discal and submarginal spots. The lower forewing is black with iridescent green submarginal and discai spots, radial band and a patch in the cell. LHW yellow-green with black veins, subdiscal spots and a narrow margin, a yellow anal area and golden areas as on the upper surface (1, 2, 3, 4, 6).
In the female the upper forewing has a dark brown ground colour with white markings including a cell spot, marginal fringe spots, submarginal and discal spots. The upper hindwing is darker than the forewing with yellow-brown distal patches and black subdiscal spots. The lower forewing and hindwing differ only in having paler markings (1, 2, 3, 4, 6).
The nominate subspecies, Ornithoptera croesus croesus, has been found only on the island of Bacan (Bachan, Batjan) in the Moluccas (Maluku). It is said to be very localized but less rare in its chosen sites than has been once thought (3). O. c. lydius occurs in the neighbouring islands of Halmahera (also known as Jailolo Gilolo or Djailolo), Ternate, Tidore, and possibly Morotai (Morty) (3). Halmahera, by far the largest of these islands, is the most important locality, and is the source of most of the recent captures of this birdwing (9).
The only known specimen of O. c. sananaensis was taken on Sanana, the most southerly of the Sula Islands (8). Sanana lies about 240 km south-west of Bachan and this distribution requires confirmation.
Habitat and Ecology
Ornithoptera croesus is a lowland butterfly in Bachan, where it occurs in swamps and other wet places (4). Its habitat has been regarded as difficult of access since the time of Alfred Russel Wallace, the discoverer of the butterfly (11). The larva and pupa of O. c. croesus have been briefly described but the larvae of O.c.lydius are stated to be unknown(3), which is surprising since many of the recently-collected specimens have been reared in captivity (9). Excellent figures of the larvae and pupae have been published, but of which subspecies is not stated (4). The foodplants are not comprehensively known but include Aristolochia gaudichaudii (4, 8).
In 1982 about 90 per cent of all forest in the northern and central Moluccas was under concession to large-scale commercial logging operations (7). In 1980 the entire production of 1 .4 million cubic metres of logs were exported and government control is reported to be slight (7). As a result, deforestation is being carried out in an irresponsible and unsustainable manner often on steep, easily eroded, slopes and with no reforestation—all in defiance of government regulations (7) . Indonesia is one of the world’s biggest timber producers but such exploitation without regard to conservation can only be short-term. Ornithoptera croesus is only one of many Moluccan endemics that are threatened by the devastating rate and nature of deforestation in the region (8).
Both O. c. croesus and O. c. lydius live in highly productive lowland forest, the most valuable timber concessions and the first areas to be deforested. There can be little doubt that O. croesus is declining in numbers and seriously at risk from further deforestation throughout its range. A further threat, the impact of which has not been assessed, is the reported use of large-scale insecticidal spraying in the swampy lowlands of Bachan (3), perhaps as a mosquito control measure.
Ornithoptera croesus has always been a much sought-after species (4, 9). From about 1979, large numbers of O. c. lydius appeared in trade. Prices were originally U.S. $90 a pair or more but by mid-1982 had fallen to $24 a pair in the U.S.A., perhaps indicating that the market had been satisfied (9). There have been no reports that O. c. lydius has been threatened by this increase in trade, but consideration might be given to the possibility of setting up a ranching programme on Halmahera.
The Halmahera group of islands, including Morotai, Bacan and Obi, has by far the greatest number of endemic species, the widest range of land form types and the most varied climate in the whole of the Moluccas (10). Sadly, there is not a single reserve established or even approved on any of these islands (1985). Seven reserves have been proposed in the National Conservation Plan for Indonesia, including one on Obi, one on Morotai, one on Bacan and four on Halmahera (10). There is no information on the likelihood of Ornithoptera croesus habitat being found within these proposed reserves and a survey is an essential preliminary step towards more specific conservation measures.
The species should be retained, until its status can be reviewed, under Appendix II of the 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Appendix II listing implies that commercial trade is allowed providing a permit from the country of export is obtained. This can provide a method of monitoring trade levels.
This page has been transcribed and edited, with permission, from Threatened Swallowtail Butterflies of the World: the IUCN Red Data Book by N.M. Collins & M.G. Morris. Whilst providing a sound baseline of information, it is in need of updating. The full volume, with references, may be downloaded from the IUCN Library System.
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- Various trade catalogues (1979-82).
- UNDP/FAO National Park Development Project (1981). National Conservation Plan for Indonesia. Vol. 7. Maluku and Irian Jaya. FAO, Bogor.
- Wallace, A.R. (1869). The Malay Archipelago. MacMillan, London. (Dover reprint edition, 1962, pp. 257-8).