Troides helena, locally known as the Common Birdwing, with its distinctive black and yellow wings, is among the most beautiful butterflies in Malaysia. It belongs to the family of Swallowtail butterflies, Papilionidae. It is a large butterfly; its forewing is about 8 cm in length with rich velvety black-edged upperparts and pale greyish streaks in the male which are broader in the female (Corbet & Pendlebury, 1992). The extent of the pale streaks varies between subspecies; in the peninsula, it is usually present in the female but vestigial or absent in the male. The hindwing is golden yellow with black veins and wavy black borders. Females have a complete series of large black spots inner to the black border while these spots are smaller or usually absent in the male.
The Common Birdwing is widely distributed from North India to South China, through Southeast Asia as far as Sulawesi (Kirton, 2014). Two subspecies are found in Malaysia; T. h. cerberus, occurs in Peninsular Malaysia (Corbet & Pendlebury, 1992) while T. h. mosychlus occurs in Sabah and Sarawak (Fruhstorfer, 1913). The Common Birdwing is a forest species that inhabits lowland and montane forests (Kirton, 2014) but is also often seen near villages, town gardens and parks near forests, with both sexes flying around flowering plants (Corbet & Pendlebury, 1992).
Tan (2011) documented the life history of T. h. cerberus where it goes through four stages, namely, egg, caterpillar (larva), pupa and butterfly. After mating with the male, the adult female will lay the eggs singly on the under surface of leaves or stems of the host plant. The eggs hatch in six days into caterpillars. The caterpillar stage consists of 5 instars and takes about 3 weeks to complete. The caterpillar feeds on the wild jungle climbers Aristolochia acuminata and A. foveolata for protection, as these plants contain aristolochic acid which is poisonous to predators (Weintraub, 1995). It stays for about 19-20 days in the pupa stage before emerging as an adult butterfly.
According to the IUCN Red List of Threatened Species, this butterfly has been assessed as Least Concern, but ironically, it is threatened due to habitat loss through wood harvesting activities (Böhm et al., 2018). In Malaysia, it is protected under the Wildlife Conservation Act 2010 (Act 716) and the trade of this species is regulated by CITES Appendix II (CITES, 2015). It is known to occur in some protected areas, for example, Imbak Valley region of Sungai Imbak Forest Reserve in Sabah, Endau Rompin National Park in Johor, nature reserves within Singapore, Gorumara National Park in West Bengal, and Bantimurung Nature Recreation Park in Indonesia (Böhm et al., 2018). However, in Indonesia, together with some other butterflies, declining populations have been reported due to collection activities (Putri, 2016).
Populations of Common Birdwing could also be locally threatened, for example, at the Forest Research Institute Malaysia, this butterfly has not been seen for several years (Phon et al., 2015). Also, in Singapore, it is considered potentially vulnerable to extinction within parts of its range (Khew & Neo, 1997). Apart from protecting its natural habitat and increasing public awareness, the population and visibility of this butterfly species can be increased and maintained by planting preferred host and nectar plants as has been reported in Singapore (in Alexandra Hospital Butterfly Trail; Khew, 2008) and Peninsular Malaysia (in Forest Research Institute Malaysia; Phon et al., 2015).
