13 January 2008

Life History of the Great Imperial

An update version of the life history of the Great Imperial can be viewed by clicking this link.

Butterfly Biodata :
Genus : Jacoona Distant, 1884
Species : anasuja C&R Felder, 1865
Subspecies : anasuja C&R Felder, 1865
Wingspan of Adult Butterfly : 36mm
Caterpillar Host Plant : Dendropthoe pentandra (Loranthaceae)

Physical Description of Adult Butterfly : The male of the Great Imperial is deep shining blue on the upperside, with a short oblique band running across the black apical border and dorsal blue patch stretching from the base of the forewing to the termen. Females are predominantly brown above, with a white tornal area on the hindwing. The underside is mainly orange, deepening towards the forewing apex, and the post-discal striae are confined to the tornal half of the hindwing. Both sexes possess a pair of white sword-like tails.

Field Observations of Butterfly Behaviour : The Great Imperial has been described as "rather rare in lowland forest". The adult butterfly appears to be a tree-top dweller and occasionally descends to feed or lay eggs. It shares the behaviour of a closely-related species, the Grand Imperial (Neocheritra amrita amrita) and resembles it closely. Where encountered, the butterfly is observed to fly rapidly, and stops to rest with its wings folded upright. Very rarely, it can be seen sunbathing with its wings opened.

Members of ButterflyCircle who have encountered this butterfly in the nature reserves described it as making "a loud buzzing sound" while in flight.

Early Stages :

The spherical egg has short blunt 'spikes' and is creamy yellow in colour. The egg is laid singly on the upper surface of the host plant leaf. The colour of the eggshell remains unchanged until the caterpillar hatches. After about 3~4 days, the caterpillar hatches from the egg and immediately eats its eggshell as its first meal, until the eggshell is completely consumed.

The newly hatched caterpillar eats its eggshell as its first meal

The 1st instar caterpillar has two reddish brown patches on each side of the abdomen with many fine setae on the body. It usually feeds on the top surface of the leaf, scraping the upper surface lamina and leaving many small crater-like circles on the leaf.

As it moults into the 2nd instar, the caterpillar has more reddish brown patches and leaves with fewer fine setae. At this stage saw-tooth spikes appear along the back of the caterpillar. The caterpillar keeps on the underside and feeds on the lower lamina. The caterpillar grows to slightly over 5mm in length.

2nd instar caterpillar of the Great Imperial

The 3rd instar caterpillar is reddish brown in colour with very few fine setae but has three big prominent "spikes" on its back. It feeds on the edge of the leaves and occasionally on the underside of the leaves as well. It measures about 9mm at the early 3rd instar.

The caterpillar camouflages itself very well, being of a similar colour as its host plant leaves.

The 4th instar caterpillar has a pointed shaped head and is earth brown in colour with 9 reddish brown spiracles, one on the thorax and the rest on the abdominal segments. The 1st spiracle near the head of the caterpillar is set further apart from the rest of the 8 spiracles.

Eighteen days after hatching, the caterpillar measures about 26mm in length.

The 5th and final instar caterpillar measures about 32~36mm in length and is mottled with reddish brown with creamy white patches near the tip of the thoracic segments as well as below the three prominent spikes and the other parts of the body as well.

Final instar caterpillar. Inset : Head shot of the caterpillar.

After a total of 27 days upon hatching from its egg, the caterpillar assumes its pre-pupation pose and remains dormant for about a day. The caterpillar prepares for pupation by attaching itself well by the cremaster without silk pad on the surface of a twig, but unlike many other species, it has no girdle to support the pupa.

The prominent protuberance at the thoracic segement at the pre-pupation stage

Anterior view of the final instar caterpillar

The pupa, attached only by its cremaster bears two prominent paired protuberances. It is grey brown in colour with a dash of powdery green spread over its body.

Thirty-four days after the caterpillar hatched from its egg, the pupa becomes semi-transparent and turns darker, where the wings of the butterfly within are discernible, whilst the abdominal segments turn a light pinkish brown.

Eclosion of the butterfly took place in the afternoon as this beautiful male specimen of the Great Imperial emerged.

A fleshly emerged male Great Imperial holding onto its empty pupa case

Text by Tan BJ ; Edited by Khew SK ; Photos by Tan BJ & Horace Tan