Butterfly Biodata:
Genus: Melanitis Fabricius, 1807
Species: leda Linnaeus, 1758
Subspecies: leda Linnaeus, 1758
Wingspan of Adult Butterfly: 50-60mm
Caterpillar Local Host Plant: Megathyrsus maximum (Poaceae, common name: Guinea Grass).
Physical Description of Adult Butterfly:
The wings have falcate (sickle-shaped) termen (outer margin), more so in the female. On the upperside, the wings are dark brown with a large sub-apical patch which is black with two white spots embedded and shaded with orange brown on the inner side. On the underside, both wings differ markedly between the wet season and dry season forms. In the wet season form, the wings are bluff or greyish brown, bearing series of transverse striae in dark brown and there is a series of submarginal black eye-spots which are white-centred and yellow-ringed. In the dry season forms, the wing markings are more cryptic and the submarginal spots are less prominent, reduced in size or even obsolete. In some specimens, the markings on the wings exhibit drastic contrast between (very) dark brown and (very) pale brown patches.
Field Observations of Butterfly Behaviour:
The Common Evening Brown is a moderately rare butterfly in Singapore. Adults are typically sighted flying at dawn and before dusk, at and around grass patches, thickets or dense vegetation. The adults fly rapidly at low level and in short hops, and have been observed to puddle on wet grounds and visiting flowers for nectar. In Singapore, the wet season form is more commonly seen than the dry season form.
Early Stages:
Worldwide, the Common Evening Brown utilizes a number of larval host plants in the Poaceae family, including Oryza sativa (Asian Rice) and Zea mays (Maize). In Singapore, so far only the grass species, Megathyrsus maximum (Guinea Grass), has been identified its larval host. The caterpillars feed on leaves of the host plant, and tend to rest lengthwise on the underside of a grass blade during pauses between feeds. The caterpillars are gregarious and often feed and rest together (in a neat row) on the leaf underside.
The eggs are laid in small clusters (clusters of 2, 3 and 6 have been observed) on the underside of a grass blade of the host plant. Each spherical egg (about 1mm in diameter) is pale translucent with a light yellowish green tinge. The surface appears to be smooth to the naked eyes.
The egg takes about 3 days to hatch. The young caterpillar nibbles away a portion of the egg shell to exit and then proceeds to devour the rest of the egg shell almost entirely. It has a cylindrical body in whitish colour, and an initial body length of about 3-3.1mm. The body is covered with dorso-lateral and lateral rows of black setae. At the posterior end, there is a pair of backward-pointing processes. Its dark colored head features a number of setae and has a pair of short and rounded horns and a few lateral protuberances.
As a result of its leaf diet, the 1st instar caterpillar soon takes on a strong greenish undertone. The first instar lasts about 3 days with the body length increases to about 6-6.8mm.
In the 2nd instar, the cephalic horns become proportionately longer and the two anal processes longer and thus pronounced. The few lateral conical protuberances are no longer present. The body is yellowish green, and the head is mostly black except for a central green patch. The body is also adorned with numerous minute whitish tubercles, each with a single seta emanating from it. Thin, lateral white bands are also present. The 2nd instar lasts about 2-2.5 days with the body length reaching about 10-11mm.
The 3rd instar caterpillar resembles the previous instar closely. The head capsule is mostly black except for the basal areas around the mouth parts which are pale lime green. The cephalic horns are again proportionately longer. This stage takes about 2-2.5 days to complete with body length reaching about 18-19mm.
The 4th instar caterpillar again has proportionately longer cephalic horns which now take on a hinge of reddish brown in its coloration. Small, lateral, white patches could be seen in the head capsule of some specimens. Otherwise, the caterpillar bears strong resemblance to those in the early two instars. The 4th instar lasts about 3.5-4 days with body length reaching about 31-32mm.
The next moult brings the caterpillar to its 5th and final instar. The body is yellowish to lime green with the head exhibiting remarkable variations in coloration and markings. The cephalic horns are usually red to reddish brown, with some being whitish on the backward side. The head proper could be black with greenish patches and white lateral patches, or entirely green with lateral whitish bands. In a period of about 4.5-5.5 days, the body grows to a maximum length of about 45-51mm.
Toward the end of the 5th instar, the body gradually shrinks in length and turn mostly yellowish green. Typically, the caterpillar will seek out a spot on the underside of a leaf blade to spin a silk pad. It then anchors itself there via its anal end, and assumes its upside-down pre-pupatory pose.
After about one day as a pre-pupa, pupation takes place. The smooth pupa is yellowish green throughout. It is slightly angular in appearance, with a dorsal keel on the thorax and ridges defining the dorsal wing margins. There are a few dark stripes in the wing pads, otherwise the pupa bears no other markings. Length of pupae: 21-22mm.
The pupation event of a Common Evening Brown butterfly.
After 6 days of development, the pupa becomes darkened in color, and the ringed-spot on the forewings can now be seen through the pupal skin in the wing pads. The next day the eclosion event takes place with the adult butterfly emerging to start the next phase of its life cycle.
The pupation event of a Common Evening Brown butterfly.
References:
- [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.
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