Life History of the Great Helen (Papilio iswara iswara)
Butterfly Biodata:
Genus: Papilio Linnaeus, 1758
Species: iswara White, 1842
Subspecies: iswara White, 1842
Wingspan of Adult Butterfly: 140mm
Caterpillar Host Plants: Maclurodendron porteri (Rutaceae)
A male Great Helen visiting a flower.
A male Great Helen visiting a flower, giving a view of its upperside
Physical Description of Adult Butterfly:
Great Helen is a large butterfly with a wing span of up to 14cm. The forewing is black above and, on both surfaces, the hindwing has a large white discal patch of four spots in spaces 4 to 7. There is a spatulate tail at each hindwing at vein 4. On the hindwing underside, there are blue post-discal lunules distal to the white spots in 2, 3 and 4. The female has a large black ocellus ringed with red in each of spaces 1a and 2 on the hindwing upperside (see the top picture in this article).
Field Observations of Butterfly Behaviour:
Locally the occurrence of this species is restricted to the Central Catchment Nature Reserves where its host plant, Maclurodendron porteri (old name: Acronychia porteri), is rather common, especially along MacRitchie Nature Trail and Nee Soon Pipeline. The adults usually fly rapidly at tree-top height, except when they come down to feed at flowering bushes or to look for oviposition sites. Like many of the Papilio species, when an adult stops to feed at flowers, it flutters its forewings while its hindwings are kept relatively still. When resting at a perch, the forewings droop backwards to almost or completely conceal the white discal patch on the hindwings.
Early Stages:
The host plant, Maclurodendron porteri, is a tree with simple, opposite and ovate leaves which are 10-18cm long. The leaves have a pleasant aromatic smell when crushed or when broken at stalks. Cancer researchers have found this plant to contain various flavonols with cancer-fighting attributes.
Host plant : Maclurodendron porteri
A female Great Helen attempting to oviposit on a leaf of the host plant
The eggs of the Great Helen are laid singly on undersides of young leaves of the host plant. Typically only one egg or one caterpillar is found on a single plant. The egg is pale creamy yellow with a finely roughened surface. It is nearly spherical with a diameter of about 1.8mm.
A fresh egg of Great Helen, diameter: 1.8mm
A mature egg, giving a faint front view of the head of the caterillar.
The egg found in the field took about 4 days to mature. The young caterpillar eats its way out of the mature egg, and then proceeds to finish up the rest of the egg shell. The newly hatched has a rather spiky appearance, and an initial body length of about 4mm. It is greyish white dorsally and dark brown laterally,
Newly hatched 1st instar caterpillar, length: 4mm
1st instar caterpillar, length: 6mm
In the first 4 instars, the Great Helen caterpillars look like bird droppings as they rest on the leaves. The resemblance in the 3rd and 4th instars are stronger with the body also assuming a slimy appearance. As in the case of all Swallowtail butterflies, the Great Helen caterpillars in all instars possess a fleshy organ called osmeterium in the prothoracic segment. Usually hidden, the osmeterium can be everted to emit a foul-smelling secretion when the caterpillar is threatened
As the 1st instar caterpillar grows to a maximum length of about 8mm, the dorsal whitish patches changes to orangy brown. There is a faint whitish saddle on the mid-abdominal segments, and white markings on the posterior abdominal segments. After about 3 days in 1st instar, the caterpillar moults to the next instar.
1st instar caterpillar, day 3 in this stage, ready to moult; length: 8mm
The 2nd instar caterpillar has a similar appearance to the late 1st instar caterpillar except for the more distinctly white saddle mark and posterior abdominal segments. This instar lasts 3 days with the body length reaching about 16mm before the next moult.
2nd instar caterpillar, length: 10.5mm
In the 3rd instar, again there is no drastic change in physical appearance except for more dark brown to black patches appearing on the mottled body, and the more distinct white saddle mark. This instar takes 3 days to complete with body length reaching 25mm.
3rd instar caterpillar, length: 25mm
The 4th instar caterpillar looks almost the same as in the 3rd instar but with a more slimy appearance. This instar lasts 4 days with body length reaching about 38mm.
4th instar caterpillar, length: 36mm
The next moult brings the caterpillar to its 5th and final instar. Now there is a drastic change in appearance. There are two eye spots on the third thoracic segment, a transverse band at abdominal segments 1 and 2 , and oblique bars at mid-abdominal segments. After the moult to 5th instar, the body ground color is initially mottled green, but this changes gradually to the characteristic smooth green color after 1 day.
5th instar caterpillar, first day after the moult, length: 39mm
Now the shield-like thorax is very prominent. The eye spots on the 3rd thoracic segment are connected by a transverse green dorsal band with sinuous markings. A similar band, but in orangy brown, occurs between abdominal segments 1 and 2, and features pale purplish gaps between the sinuous markings. The first oblique bars, one on each side, run from the base of abdominal segment 3 to the top of segment 4. The second oblique bars occur at the two sides of abdominal segment 5, wide at the base and tapering to the dorsum. Both sets of oblique bars are mainly greenish brown dotted with tiny pale purple spots.
5th instar caterpillar, late in this stage, length: 65mm
The 5th instar lasts for 8 days, and the body length reaches up to 65mm. Toward the end of this instar, the body gradually shortens in length. Eventually the caterpillar comes to rest on the lower surface of a stem and becomes a pre-pupatory larva.
A pre-pupatory larva of Great Helen
Pupation takes place a day later. The pupa suspends itself with a silk girdle from the stem. It is mottled in shades of brown, green and white. The pupa has cephalic horns and a dorsal thoracic hump, and is angled in side view. Length of pupae: 36-37mm.
Pupa of Great Helen; fresh on left and mature on right
After 13-15 days of development, the pupa turns black as the development within the pupal case comes to an end. The next day the adult butterfly emerges from the pupal case. The beautiful undersides of its wings are fully displayed as it dries its wings for the first few hours after eclosion.
A newly eclosed female Great Helen drying its wings near the empty pupal case
A newly eclosed male Great Helen
Acknowledgments:
I would like to express my gratitude to Samsuri Ahmad of NParks for generous assistance in the identification of the host plant.
References:
- 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 Press 1999
- Plants that Fight Cancer, S.E. Kintzios, M.G. Barberaki, CRC Press 2004
