22 October 2011

Life History of the Common Mormon

Life History of the Common Mormon (Papilio polytes romulus)

Butterfly Biodata:
Genus: Papilio Linnaeus, 1758
Species: polytes
Linnaeus, 1758
Subspecies: romulus
Cramer, 1775
Wingspan of Adult Butterfly: 70-85mm
Caterpillar Host Plants:
Murraya koenigii (Rutaceae, Common Name: Indian Curry Leaf), Merope angulata (Rutaceae, common name: Mangrove Lime),  Citrus maxima (Rutaceae, common name: Pomelo), Citrus aurantifolia (Rutaceae, common name: Lime) and other Citrus spp.

A female form -polytes  Common Mormon sunbathing on a leaf.

A male Common Mormon puddling in the western nature reserve.

A male Common  Mormon puddling on damp ground.

Physical Description of Adult Butterfly:
Above, the  male is black with a band of large whitish yellow spot running across the hindiwng. This band appears to continue to the forewing in the form of several white spots on the distal margin of the forewing. In Singapore, the female appears in two forms: form -polytes which mimics the Common Rose but with an entirely black abdomen; form -cyrus which resembles the male but has a red tornal spot in space 1a of the hindwing. Underneath, the male has a series of yellow to red submarginal lunules on the hindwing, while the female form -polytes  again resembling the male and  form -cyrus resembling that of the Common Rose. Both sexes have a spatulate tail at vein 4 of the hindwing.

A female form -polytes Common Mormon visiting a flower.

A female form -cyrus Common Mormon

Another puddling male Common Mormon.

Field Observations of Butterfly Behaviour: 
Common Mormon is rather common in Singapore and can be found in both forested and urban areas in Singapore. The fast flying adults visit flowers for energy intakes and the males can be found puddling on damp grounds in their habitat. In urban settings, the adults can be found in housing areas and gardens where Citrus plants are grown.

Early Stages:
The local host plants include the Indian Curry Leaf plant and various Citrus spp. One notable addition is the Mangrove Lime (Merope angulata) which was found to be utilized as larval host plant by members of the Plant Systematics group of the Department of Biological Sciences (NUS) in the recent past. The caterpillars of the Common Mime feed on the young to middle-aged leaves of the host plants.

Host plant : Citrus maxima. Left: Young leaves and mature leaves. Right: a Pomelo fruit.

A mating pair of the Common Mormon with the female giving us a full view of its upperside.

The eggs of the Common Mormon are laid singly on the young stem, the petiole or the underside of leaves of the host plant. The egg is pale creamy yellow with a finely roughened surface. It is nearly spherical with a diameter of about 1.2mm.

A mother Common Mormon about to oviposit on a lime plant.

Two views of an egg of Common Mormon, diameter: 1.2mm

Two views of a mature egg, giving a faint front view of the head of the caterpillar.

The egg takes about 3 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 3mm. It is yellowish brown dorsally and dark brown laterally.

Two views of a newly hatched 1st instar caterpillar, length: 3mm.

Two views of a 1st instar caterpillar, length: 3.6mm

In the first 4 instars, the Common Mormon caterpillars resemble 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 the 1st instar caterpillar grows up to a length of about 5-6mm, the dorsal and dorso-lateral  whitish patch at the posterior segments become more prominent. There is a faint whitish saddle on the 3rd-4th abdominal segments. After about 3 days in 1st instar, the caterpillar moults to the next instar.

Two views of a 1st instar caterpillar, late in this stage, length: 4.8mm

The 2nd instar caterpillar has a similar appearance to the late 1st instar caterpillar except for the more distinctly white markings on the middle and posterior body segments, and traces of white on anterior segments. This instar lasts 2-3 days with the body length reaching about 10mm before the next moult.

Two views of a 2nd instar caterpillar, newly moulted, length: 5.2mm

Two views of  a 2nd instar caterpillar, late in this stage, length: 9.5mm.

The newly moulted 3rd instar caterpillar bears no drastic change in physical appearance except for more dark brown to black patches appearing on the mottled body, and the more prominent white saddle mark. This instar takes about 2.5-3 days to complete with the body length reaching up to 16mm.

Two views of a 3rd instar caterpillar, early in this stage, length: 12.5mm.

Two views of a 3rd instar caterpillar, late in this stage, length: 16mm.

The 4th instar caterpillar resembles the late 3rd instar caterpillar initially but with a more slimy appearance and stronger green undertone. As growth proceeds, the cryptic markings of light to dark green intermingled with white streaks becomes increasing mottled. This instar lasts about 2-3 days with body length reaching about 25-26mm.

A 3rd (left) and  a 4th (right)  instar caterpillar found on a Lime plant in a garden.

Two views of a 4th instar caterpillar, early in this stage, length: 21mm.

Two views of a 4th instar caterpillar, late in this stage, length: 26mm

The next moult brings the caterpillar to its 5th and final instar with a drastic change in appearance.  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.

Two views of a 5th instar caterpillar, early in this stage, length: 30mm.

Two views of a 5th instar caterpillar,  length: 36mm

The eye spots on the 3rd thoracic segment are connected by a transverse green dorsal band with sinuous markings. A similar band occurs between the 3rd thoracic and the 1st abdominal segments, and features pale purplish bluish 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 is much shorter and occur at the two sides of abdominal segment 5.

Two views of a 5th instar caterpillar, late in this stage, length: 45mm

As in the case of all Swallowtail butterflies, the Common Mormon 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.

A Common Mormon caterpillar everting its osmeterium.

The 5th instar lasts for 5-6 days, and the body length reaches up to 45-46mm. 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 the Common Mormon.

A Common Mormon caterpillar molts to its pupal stage.

Pupation takes place a day later. The pupa suspends itself with a silk girdle from the stem. There are two color forms. In the green form, the pupa is is mainly green with a large yellowish diamond-shaped on the dorsum of the abdominal segments..  In the brown form, the pupa is manly greyish to darker shades of brown. Each pupa has a pair of  cephalic horns, a dorsal thoracic hump and is angled in side view. Length of pupae: 31-32mm.

Two views of a Common Mormon pupa.

A mature pupa of the Common Mormon.

After 8   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 Common Mormon clinging on to its empty pupal case

A newly eclosed male Common Mormon resting near its empty pupal case

  • [C&P4] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society.
  • Butterflies of Thailand, Pisuth Ek-Amnuay, 2nd Edition, 2012.
  • A Field Guide to the Butterflies of Singapore, Khew S.K., Ink On Paper Communications, 2010.

Text by Horace Tan, Photos by Benjamin Yam, James Chia, Benedict Tay,  Ellen Tan, Nelson Ong,  Bobby Mun, Anthony Wong, Federick Ho, Sunny Chir and Horace Tan