26 January 2008

Life History of the Malay Viscount

Life History of the Malay Viscount (Tanaecia pelea pelea)
An updated version of the life history of the Malay Viscount can be found by clicking this link.

Butterfly Biodata :
Genus : Tanaecia Butler, 1839
Species : pelea Fabricius, 1787
Subspecies : pelea Fabricius, 1787
Wingspan of Adult Butterfly : 70mm
Caterpillar Host Plant :
Palaquium obovatum (Sapotaceae).
Physical Description of Adult Butterfly : The upperside of the Malay Viscount is a pale greyish ochreous brown, with sub-marginal V-shaped markings on white background. The V-shaped markings are conjoined. The underside is paler, with a faint tinge of violet in a sidelight. In the male, the underside of the hindwing has two rows of small black submarginal separated V-shaped markings whilst these are less distinct, and joined in the female.

Field Observations of Butterfly Behaviour : The Malay Viscount is a forest denizen which is rarely seen outside the nature reserves and forested areas of Singapore. It is relatively common and both sexes are often seen puddling on rotting fruit, carrion or at damp seepages. It flies in the typical Tanaecia or Euthalia fashion, gliding powerfully as it flaps its wings. It is a skittish butterfly, and when disturbed, takes off in a very capable fashion.

Mating pair of Malay Viscount - left-male ; right-female. Note the differences in the underside markings between the two sexes.

Early Stages : The female oviposits on the underside of a mature leaf (usually at the centre) of the host plant. This is quite unlike its close relative, the Horsfield's Baron (Tanaecia iapis puseda), where the female searches for a leaf, and reverses till her abdomen touches the tip of the hostplant leaf, and oviposits on the tip of the leaf. In the Malay Viscount, the female touches the veins of the leaf of the host plant, and oviposits a single egg on the underside of the selected leaf.

Two views of the Malay Viscount egg.
After about four days, the 1st instar caterpillar hatches from the egg, and makes its first meal of the eggshell. The caterpillar crawls towards a younger leaf and proceeds to munch on the leaf edge. The 1st instar caterpillar is yellow-green with simple white-tipped black spines from its body.

1st instar caterpillar

After eating for about 2 days, the caterpillar moults and changes into its 2nd instar. The caterpillar now sports branched spines which radiate horizontally and flat, away from its body. The spines are a pale cream. The caterpillar eats very little, making small cuts along the host plant's leaf edge.

2nd instar caterpillar, sporting its flat branched spines radiating horizontally from its body

At the 3rd instar, the caterpillar's branched spines are now green, with black/white fine hairs giving it the characteristic "Christmas Tree" appearance of many species of this genus and its related genera of Euthalia and Lexias. The caterpillar now has a series of oval greyish purple-centred spots along its back.

A 3rd instar caterpillar showing its purple spots along its back

The 4th instar caterpillar appears quite similar to the 3rd instar, except that it is now much bigger, and the oval purple-centred spots are more distinctly marked and fringed with white with a thin black border. The branched spines are also longer and end with a curved T-shaped hooked spines.

4th instar caterpillar eating along the edge of its host plant leaf

The 5th instar caterpillar has additional whitish spots along its body, whilst the white-fringed purple spots along its back are still prominently displayed. The branched spines are also more complex, and gives the caterpillar an appearance of being a lot larger than it really is. It moves slowly, but eats voraciously - finishing almost a single large leaf in about two days.

A 5th instar caterpillar next to a 3rd instar caterpillar of the Malay Viscount. Note the relative size between the two caterpillars.

Detail of a 5th instar caterpillar, showing its complex branched spines and the row of whitish fringed purple spots along its back.

After about 17 days, the 5th instar caterpillar shrinks in length, and the large purple spots along its back become less distinct. A white saddle stripe appears. Later in the day, the caterpillar turns a yellowish green and stays in this pose until pupation occurs. Pupationg may occur on the top or under surface of a leaf of the host plant. The pre-pupating caterpillar anchors itself securely via its cremaster.

Pre-pupating caterpillar. Compare the markings with the 5th instar caterpillar

The pupa hangs vertially from its cremaster without the need for a girdle or any other support. The light green pupa sports a series of gold-coloured spots which are highly reflective. After about nine days, the pupa turns dark, and the pupa shell becomes transparent the night before eclosion. The wing patterns of the butterfly can be seen clearly through the transparent pupa shell.

Different views of the pupa of the Malay Viscount. Note the gold spots. The wing patterns of the adult butterfly are visible through the transparent pupa shell on the night before eclosion

The Malay Viscount ecloses relatively early in the morning between the hours of 8am and 10am when the sun is warm enough.

A freshly-eclosed female Malay Viscount holding on to its pupa shell before taking off when her wings are properly dried

Female Malay Viscount spreading her wings to sunbathe

A male Malay Viscount feeding on an overripe Ficus fruit along a trail in the nature reserves

Text & Photos by Khew SK