20 January 2008

The Flying Tigers of Singapore

Featuring the Five Flying TIGERS of Singapore

Not of the feline variety, but butterflies (what else?!).

Singapore is home to five species of butterflies from the sub-family Danainae which have been given the common name "TIGER". The origin of the common name probably referred to the striped wing patterns and, in a number of species, the orange colour of the wings.

The sub-family Danainae features medium sized to large butterflies which are showy, and tend to fly slowly and gracefully. As they fly from flower to flower in search of nectar, one can appreciate their beauty and colours at close range. There is an explanation for their nonchalance and devil-may-care behaviour, due to the fact that almost all the species in the sub-family have "built-in" immunity to predators. In their early stages as leaf-munching caterpillars, the species of this sub-family feed on lactiferous vines and plants which makes the caterpillars and later on, the adult butterflies, distasteful to birds and other predators.

The very obvious markings and colours of the Danainae species is a purposeful 'advertisement' to predators that they are unpleasant to eat, and to stay away from them. So successful is this display, that several other species of butterflies, which do not have this protection, mimics the colours and patterns of the Danainae to benefit from their immunity to predators.

The five Tiger species found in Singapore are :

  • Plain Tiger (Danaus chrysippus chrysippus)
  • Common Tiger (Danaus genutia genutia)
  • Black Veined Tiger (Danaus melanippus hegesippus)
  • Blue Glassy Tiger (Ideopsis vulgaris macrina)
  • Dark Glassy Tiger (Parantica agleoides agleiodes)

The Plain Tiger is probably the commonest Danaus species and is found in parks and gardens where its preferred host plant, Calotropis gigantea is cultivated. The Plain Tiger has orange forewings with a broad black apical border bearing a series of white spots. It occurs in two forms where form-chrysippus has its hindwing coloured orange as in the forewings. This form occurs more often in northern Malaysia (Penang, Kedah and Langkawi Islands) and in Singapore.

The white hindwinged form-alcippoides is more common in the rest of Malaysia, but also occurs commonly in Singapore. Generally, this form is the more predominant form of the species in Singapore, outnumbering the orange-hindwinged form-chrysippus by at least 10:1 during a survey of the species in 2004.

Where the host plant is found, one can often find the droppings of of the caterpillars on the large leaves of Calotropis gigantea. It is not unusual to find a large number of the caterpillars on a single plant where the entire plant may defoliated in matter of weeks.

The Common Tiger has the same colouring as the Plain Tiger, except that its wings' veins are strongly marked with black. Sometimes almost as common as the Plain Tiger, the Common Tiger is often found in mangrove areas where its host plant, a lactiferous vine, Raphistemma sp. grows.

As in the case of the Plain Tiger, the Common Tiger occurs in two forms. - the orange hindwinged form-genutia and the white hindwing with orange-tinged border form-intermedius. In Singapore, both forms occur, but again, like the Plain Tiger, the white with orange-tinged border form is the commoner of the two.

The Black Veined Tiger is the least common of the three Danaus species in Singapore. This species is very similar to the Common Tiger and is often mis-identified as such. However, the difference is that the white hindwings do not have an orange tinge as in the form-intermedius of the Common Tiger. The black hindwing border is also much wider than in the Common Tiger. On the offshore island of Pulau Tekong, the Black Veined Tiger is the predominant species and is much more common than the Common Tiger, as compared to the main island of Singapore.

The males of all three Danaus species possess an oval brand enclosing scent scales on the hindwing which appears as a black bordered pouch. The females do not have this feature.

The Blue Glassy Tiger belongs to the genus Ideopsis. It is the only representative of the genus in Singapore. The wings are predominantly a translucent bluish grey, with the veins blackened, giving the butterfly a striped appearance. The Blue Glassy Tiger is common in Singapore, and can be found in gardens, parks and within the nature reserves.

Its lactiferous host plant, Tylophora sp. is a common vine growing in secondary vegetation and particularly in the mangrove areas. The species is likely to have several other alternative host plants.

The Dark Glassy Tiger which, at a glance, appears like the Blue Glassy Tiger, is the only representative of the genus Parantica in Singapore. Its closely related cousin, the Yellow Glassy Tiger (Parantica aspasia aspasia) has not been seen in Singapore for a long time, and feared extinct. The ground colour of the Dark Glassy Tiger appears less bluish in flight, giving a more greyish appearance. It can be distinguished from its lookalike, in that the forewing cell streaks of the Dark Glassy Tiger contain thin longitudinal black lines, whereas there is a diagonal black bar in the Blue Glassy Tiger's forewing cell.

Both the Blue and Dark Glassy Tigers often occur together in the same vicinity and both are common butterflies in Singapore. The males can be separated from the females by the darkened brands at the sub-tornal area of the hindwing.

All the five Tigers are slow flyers and often stop to feed at flowering plants. They are relatively easy subjects to photograph, and are very likely to feature in any enthusiastic butterfly photographer's portfolio of butterfly pictures. All the species are attracted to the flowers of the Indian Heliotrope (Heliotropium indicum) and in particular, the semi-dried leaves and stalks of this plant are particularly attractive to the Tigers.

Text by Khew SK ; Photos by Khew SK, Simon Sng & Wong CM