17 November 2019

Flight of the Imperials

Flight of the Imperials
Featuring Singapore's Imperial Butterflies

A Branded Imperial perches on a leaf in the shaded forest understorey

The English word "imperial" is usually used to refer to things or people that are or were connected with an empire or pertaining to an emperor or empress. When the early collectors coined the name Imperial for some species of the Lycaenidae family, it is highly likely that they were using the word to describe these majestic butterflies that awed them with their breath-taking colours and beauty.

A Green Imperial stops to rest on the flower of the Javanese Ixora

In the world of butterflies, the Imperials are pretty, colourful and usually long-tailed species belonging to the sub-family Theclinae of the Lycaenidae family. Singapore is home to five of these Imperials, all of which are forest-dependent and usually found only in the heavily forested nature reserves. Of the five, only one is considered common and regularly seen by nature enthusiasts.

A female Great Imperial feeding on the flower of the Javanese Ixora

This blogpost takes a look at these five Imperial butterflies found in Singapore. Interestingly, each one of the five belongs to a different genus. All have orange with white undersides and black tornal markings. Their long tails are remarkable features on these species, and two of them probably sport the longest tails amongst the extant butterflies in Singapore.

1. The Branded Imperial (Eooxylides tharis distanti)

A Branded Imperial shares the sweet sap of the Bandicoot Berry with some ants

The first of the Imperials is the Branded Imperial. This species is by far the commonest of the five species and is regularly found along forest paths in the shaded understorey of our nature reserves. At times, several individuals can be seen together, particularly when they are feeding on the young shoots of the Bandicoot Berry (Leea indica).

A male Branded Imperial opens its wings to sunbathe.  Note the prominent brands on its forewings

The wings are black above with blue-dusted tornal area on the hindwing. In the male, a prominent "brand" can be seen on the upperside of the forewing. This could be why the butterfly is named Branded Imperial. The underside is reddish-orange with the hindwing bearing black sub-marginal spots on the white tornal area. There are 3 tails on the hindwing, of which the one along vein 2 is the longest.

The species' caterpillar feeds on the invasive weed Smilax bracteata which it shares with another Lycaenid, the Yamfly. As this non-native weed is very widespread in the nature reserves (despite efforts to remove the weed), the Branded Imperial has become a common species in Singapore.

2. The Common Imperial (Cheritra freja friggia)

The Common Imperial is a moderately rare species but is quite widespread across the island. Although found in the forested nature reserves, it can sometimes be found in urban parks and forested ridges in Singapore. It is usually observed singly and prefers to stay at treetops. It has a habit of perching on favourite leaves and returns time and again to the same perches as it flies around.

A male Common Imperial sunbathing with its wings opened to show the purple-blue uppersides

The male Common Imperial has purple-blue forewings on the upperside, whilst the female is dark brown. There are large black spots on the tornal area of the hindwing. Te underside is mainly white, with part of the forewing and the apical area of the hindwing shaded a light orange. The tornal spots on the hindwing are overlaid with metallic blue-green scaling. It has 3 tails of which the one at vein 2 is the longest.

The species' caterpillars feed on two species of common roadside trees, the Wild Cinnamon and the Red Saga. It has also been bred on other forest plants that are mainly found in the nature reserves. The species is observed to sunbathe with open wings at certain hours of the day at sunlit spots.

3. The Green Imperial (Manto hypoleuca terana)

The Green Imperial is considered rare in Singapore. It is usually seen at the forest edges of the nature reserves, feeding on the nectar of flowering plants. It is a fast-flying species that probably prefers to stay at the treetops.

The male of the Green Imperial is a shining bluish-green above, with broad black apical area on the forewing. The underside is largely orange and unmarked on the forewing, whilst the hindwing has black sub-marginal spots and streaks. The female is dark blackish-brown above with the usual black spots on a white tornal area on the hindwing. The underside of the dorsal area of hindwing is white, whilst the other areas of the forewing and hindwing are orange. The species has 2 tails - a relatively long tail and vein 2 and a short stubby one at vein 3.

Female Green Imperial. Top : Underside Bottom : Upperside

The species is one of several rare Lycaenidae that feeds on the parasitic plant, Macrosolen cochinchinensis, that can be found growing on large trees and bushes all around the island. The females have been observed ovipositing on the leaves of the host plant in the early afternoon and lays her eggs on the young shoots of the plant.

4. The Great Imperial (Jacoona anasuja anasuja)

Another rare Imperial, the Great Imperial has been observed only in the forested nature reserves of Singapore. The adult butterfly appears to be another tree-top dweller but occasionally can be seen to descend to low level shrubbery to feed or oviposit. When disturbed, it can fly rapidly up the treetops.

Top : Female Great Imperial Bottom : Male Great Imperial

The male of the Great Imperial is a deep shining blue on the upperside with an oblique band running across the apical area of the forewing. The female is predominantly brown above with a white tornal area on the hindwing. The underside is mainly orange with the forewing apical area a darker shade. The dorsal area of the hindwing is white with the tornal black streaks and spots. Both sexes have tails, where the males have a shorter sword-like tail at vein 2 whilst the female's tail is much longer.

The caterpillar host plant of the Great Imperial is the common Malayan Mistletoe. However, the species is not usually found in urban parks and gardens. It is found along the forest fringes and where it is observed, it is perched on the uppersides of leaves with its wings folded upright. Both sexes also descend from the treetops to feed on flowering plants.

5. The Grand Imperial (Neocheritra amrita amrita)

The last of the Imperials is also a rare forest-dependent species that is quite local in distribution. Its caterpillar host plant is found in the nature reserves and is quite rare. The plant has yet to be positively identified. However, the Grand Imperial was seen in numbers on the military-training island of Pulau Tekong in the early 2000's during a period of biodiversity surveys. It is not known if they are currently still as common.

A male Grand Imperial feeding on flowers

The male Grand Imperial has a royal blue upperside, with the apical areas of both wings black bordered. The female is dark brown and largely unmarked, except at the white tornal area where there are black spots. The underside of the forewing and costal half of the hindwing is dark orange whilst the remaining part of the dorsal area of the hindwing is pure white.

A female Grand Imperial sunbathing

The Grand Imperial has the longest tails of any Lycaenidae found in Singapore. It has 3 tails, of which the longest tail is at vein 2, whilst there are two shorter tails at veins 1b and 3 of the hindwing. The male has a prominent raised 'disc' on the underside of the forewing.

Text by Khew SK : Photos by Huang CJ, Khew SK, Simon Sng, Jonathan Soong, Horace Tan and Tea Yi Kai