16 November 2008

Life History of the Chocolate Royal

Life History of the Chocolate Royal (Remelana jangala travana)

Butterfly Biodata:
Genus: Remelana Moore, 1884
Species: jangala Horsfield, 1829
travana Hewitson, 1865
Wingspan of Adult Butterfly: 35mm
Caterpillar Host Plants:
Eurya acuminata (Theaceae)

Physical Description of Adult Butterfly:
Above, the male is a deep lustrous purple, with broad brown to dark brown bordering on both wings; the female is paler, and differs from the male also in that the basal portions of spaces 2 and 3 on the forewing are entirely purple. The under surface is dark brown, with conspicuous end-cell bars and a narrow, darker brown, post-discal line on both wings. The two prominent black tornal spots (the one in space 1a larger than the other in space 2) on the hindwing are crowned with brilliant metallic green scaling. Each hindwing has two white-tipped tails of equal length at veins 1b and 2.

Field Observations of Butterfly Behaviour:
This species is is rather rare in Singapore in recent times and sightings have been very infrequent over the last few years. Its occurrences appear to be restricted to a few areas in the the Central Catchment Nature Reserve.

Early Stages:
The host plant, Eurya acuminata, has been described in the life history article for Narrow Spark. Thus far, it has been recorded as the local host plant for Narrow Spark, Chocolate Royal and Ambon Onyx. The caterpillars of Chocolate Royal feed on flower buds of this plant almost exclusively in all four instars. The only exception being in the final instar when leaves are also eaten if flower buds become scarce. It is possible that Chocolate Royal has at least one other host plant locally. Once, a female was observed to oviposit an egg on an Ixora bush. Unfortunately the young caterpillar did not survive past its first instar then.

Host plant : Eurya acuminata
On a flowering host plant in the nature reserve, the mother butterfly was observed to lay eggs singly on the underside of a number of leaves. Each egg is white, but with a strong greenish tinge when freshly laid; circular
and covered with rather large hexagonal pits. The diameter is about 0.7mm.

An egg of the Chocolate Royal. Left: fresh egg; Right: empty egg shell.

1st instar caterpillar, newly hatched, length: 0.9mm

It takes 2.5 to 3 days for the egg to hatch. The young caterpillar nibbles away the upper portion of the egg shell to emerge. With a length of about 0.9mm, it is cylindrical with very long setae (hairs) and pale yellow in base color. Yellowish brown bands run dorso-laterally along its body. As it grows, the body assumes the more typical onisciform (woodlouse) shape.

1st instar caterpillar, length: 2mm

The 1st instar caterpillar finds its way to nearby flower buds and feeds by boring a hole into a flower bud and eating the interior flower parts. After 3 days of growth, and reaching a length of about 2.5mm, its moults to the next instar. The second instar caterpillar has shorter hairs covering its body. The prothoracic shield is roughly diamond in shape and black to dark brown in colour. The prominent dorso-lateral yellowish brown bands were present initially but they fade away during this instar which lasts about 4 days. As the bands fade away, the entire body assumes a light green coloration. The inconspicuous dorsal nectary organ can be seen with a close-up examination.

2nd instar caterpillar, early in thist stage, length: 2.9mm

2nd instar caterpillar, length:5mm
2nd instar caterpillar, late in this stage, length: 7mm

The 2nd instar caterpillar reaches a maximum length of about 7mm. The moult to the 3rd instar brings few obvious changes. The entire body is now covered in very shot fine hairs, and a dorsal nectary organ becomes prominently marked in reddisk brown with a central white patch. The 3rd instar takes 3 days to complete with the body length reaching about 12-13mm.

3rd instar caterpillar, early in this stage, length: 7.5mm

3rd instar caterpillar, late in this stage, length: 13mm

The 4th (and final) instar caterpillar has the same general appearance as the 3rd instar caterpillar. The prothoracic segment is covered with light brown spot while the prothoracic shield is yellowish brown in contrast. This takes about 4 days to complete with the body length reaching 21-22mm. As it grows, the caterpillar becomes more greenish in coloration. Nearing the end of this instar, the caterpillar ceases feeding, and its body shrinks in length. It finds its way to a leaf and takes up a position on the surface to become an immobile pre-pupa.

Close-up views on parts of a 4th instar caterpillar.
Left: the first two horacic segment showing the diamond-shaped prothoracic shield;
Right: dorsal nectary organ

4th instar caterpillar, early in this stage, length: 13mm

4th instar caterpillar, late in this stage, 22mm

The pre-pupatory caterpillar prepares for pupation by spinning a silk girdle and a silk pad to which it attaches itself via claspers. Pupation takes place after about 1 day of pre-pupal stage. The pupa has the typical lycaenid shape, though somewhat wider in proportion, and a length of about 11.5-12.5mm. It is entirely jade green in coloration.

Two views of a pre-pupa of the Chocolate Royal with the silk girdle featured

Two views of a fresh pupa of the Chocolate Royal

Six days later, the pupa becomes darkened in color signaling the imminent emergence of the adult. The uppersides of the forewings become visible through the now transparent pupal skin. The next day the adult butterfly emerges from the mature pupa.

Two views of a mature pupa of the Chocolate Royal

A Chocolate Royal resting on the underside of a leaf

Another Chocolate Royal found in the nature reserve


  • The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society.

  • The Butterflies of Hong Kong, M. Bascombe, G. Johnston, F. Bascombe, Princeton University Pres 1999
Text and Photos by Horace Tan

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