10 January 2009

Life History of the Common Mime

Life History of the Common Mime (Chilasa clytia clytia)

Butterfly Biodata:
Genus: Chilasa Moore, 1991
Species: clytia
Linnaeus, 1758
Subspecies: clytia
Linnaeus, 1758
Wingspan of Adult Butterfly: 95mm
Local Caterpillar Host Plant: Cinnamomum iners (Lauraceae)
[Synonym: C. initidum, C. paraneuron]
A Common Mime visiting flowers with wings fully opened giving us a full view of its upperside

A Common Mime taking nectar from Lantana in an urban hill park

A Common Mime puddling on a wet sandy area in the nature reserves

Physical Description of Adult Butterfly:
Worldwide, the Common Mime occurs in two morph-groups in both sexes, but In Singapore, only the black-and-white striped form-dissimilis occurs. This form is velvety black with extensive white streaks and spots on the upperside. Underside is similar to the upperside with slightly larger white markings, and on the hindwing there is a row of conspicuous yellow marginal spots. Head, thorax and abdomen are black with prominent white spots.

Field Observations of Butterfly Behaviour: The Common Mime is relatively common in Singapore, and can be seen in both the nature reserves and developed areas. The butterfly mimics the distasteful Danainae species for protection against predators. When the adults visit flowering shrubs, their slow and graceful flight resemble those of the distasteful Blue Glassy Tiger and the Dark Glassy Tiger. The adults have the habit of puddling on wet grounds.
Early Stages:
Across the range where this species occurs, the early stages feed on leaves of serveral plants in the Lauraceae family. The sole recorded local host plant, Cinnamomum iners (Common name: Clover Cinnamon, Wild Cinnamon), is a very common plant all over Singapore, readily found in nature reserves, gardens, parks and wastelands etc. It is a small to medium-sized tree with 3-nerved leaves. Eggs and early stages of the Common Mime are typically found on saplings at heights from knee to waist level.

Host plant : Cinnamomum iners

A female Common Mime taking off after an egg was laid on a wild cinnamon sapling.
Can you spot the egg?

The eggs of the Common Mime are laid on young leaves or petioles of a sapling of the host plant. Sometimes a few eggs could be found on the same sapling, and occasionally in close proximity. The spherical egg is creamy white with the surface coated with a non-uniform layer of orange-yellow granulated substance. Diameter: 1.2-1.3mm.

Left: egg freshly laid as featured in the previous picture.
Right: a group of three eggs on the petiole of a young leaf

Left: freshly laid egg; Middle: developing egg; Right: mature egg

The egg takes 3 days to hatch. 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 dark brown head, rows of short dorsal-lateral tubercles with long setae, and an initial body length of about 3mm. It is mainly pale brown with white patches on the the middle and posterior segments.

Newly hatched Common Mime caterpillar eating egg shell, length: 3mm

As it feeds and grows, the body color darkens to feature black lateral markings, and both yellowish brown and whitish dorsal patches. The head capsule also turns black. In this and the next three instars, the Common Mime caterpillars resemble bird droppings as they rest on the leaf surface.

1st instar caterpillar, length: 3p5mm

As the 1st instar caterpillar grows to a length of about 6.5mm, the dark lateral markings decolorizes and disappears. There is a white saddle on the 3rd-4th abdominal segments and white markings on the posterior abdominal segments. After about 2-3 days in 1st instar, the caterpillar moults to the next instar.

1st instar caterpillar, length: 5mm (top); 6.5mm (bottom)

The 2nd instar caterpillar has a similar appearance to the 1st instar caterpillar except for the longer and stubby processes, brighter shade of orange on dorsal patches, and distinctly white color on the saddle mark and posterior abdominal segments.
The growth is rather rapid and this instar lasts only 1-2 days. The body length reaches about 10-11mm before the next moult.

2nd instar caterpillar, early in this stage, length: 10.5mm

In the 3rd instar, again there is no drastic change in physical appearance except for the greater contrast between the black and orange markings. This instar takes 2 days to complete with body grown to about 19mm in length.

3rd instar caterpillar, early in this stage, length: 11mm

A time-lapse sequence of the moulting from the 3rd to the 4th instar

The 4th instar caterpillar has more extensive white markings on it body. The white patch on the posterior abdominal segments has extended to the whole of abdominal segment 7 and white lateral patches appear on the thoracic segments. This instar lasts 3 days with body length reaching about 33mm.

4th instar caterpillar, early in this stage, length: 20mm

A 4th instar Common Mime caterpillar found in the Jurong Lake area

The next moult brings the caterpillar to the 5th and final instar with a dramatic change in appearance. The body is dark greyish black in base color with numerous inconspicuous black spots embedded. On each side of the body, there are two rows of fleshy processes on segments 1 to 4 and single row on the other segments. A crimson red spot is featured at the base of each fleshy process. A sub-spiracular row of crimson red spot also occurs in the abdominal segments. The body also features large creamy yellow patches organized as follows: 1) a dorsal row of large irregularly-shaped patches; 2) a short lateral row on the posterior abdominal segments starting from abdominal segment 7, and 3) a front lateral row of yellow patches spanning all thoracic segments and abdominal segments 1, 2 and 3. The front lateral row connects with the dorsal row in abdominal segment 3.

5th instar caterpillar, second day after the moult, length: 50mm

A 5th instar Common Mime caterpillar found in a clearing in the Southern Ridges.

All instars of the Common Mime possess a fleshy organ called osmeterium in the prothoracic segment. Usually hidden, the osmeterium can be everted to surprise any intruder when the caterpillar senses the threat, The osmeterium is pale brown in the first four instars, and light indigo-blue in the final instar.

Partially everted osmeterium of a 1st intar Common Mime caterpillar

The dark to light brown osmeterium of a 4th instar Common Mime caterpillar

The indigo blue osmeterium of a final instar Common Mime caterpillar

The 5th instar lasts for 4 days, and the body length reaches up to 55mm. 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 Common Mime.
Top: preparing its anchor point; Bottom: having completed its silk girdle

Pupation takes place a day later. The pupa suspends itself with a silk girdle from the stem. The pupa resembles a broken twig about 38-40mm long, brownish with streaks and blotches,. The posterior segment is so modified that the pupa appears to have grown out of the branch to which the pupa anchors.

A Common Mime caterpillar molts to its pupal stage. [Added on 29 May 2011]

Two views of a twig-like pupa of the Common Mime.

After 11-12 days, the pupa turns black as the development within the pupal case draws to a close. The white spots on the forewings are now visible through the pupal skin at the wing pad area. The next morning the adult butterfly emerges from the pupal case.

An animated time-lapse sequence of the early portion of the eclosion event.

The eclosion of the Common Mime in a grid mosaic.

A newly eclosed Common Mime drying its wings near the empty pupal case

A newly eclosed Common Mime

  • 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
Text by Horace Tan, Photos by Bobby Mun, Federick Ho, James Chia, Khew SK and Horace Tan