02 August 2014

Life History of the Long Brand Bush Brown

Life History of Long Brand Bush Brown (Mycalesis visala phamis)

Butterfly Biodata:
Genus: Mycalesis Hübner, 1818
Species: visala Moore, 1858
Subspecies: phamis Talbot & Corbet, 1939
Wingspan of Adult Butterfly: 40-50mm
Caterpillar Local Host Plants: Isachne globosa (Poaceae), Ottochloa nodosa (Poaceae).

Physical Description of Adult Butterfly:
On the upperside, the wings are dull brown with an obscure yellow-ringed ocellus in space 2 of the forewing, and two obscure ocelli in spaces 2 and 3 of the hindwing. On the underside, both wings are pale brown in ground colour and have a whitish post-discal band. There is a series of ringed ocelli in the submarginal area on both wings. At times, a rare dry season form could be observed in Singapore where these ocelli are much reduced in size. The male has a yellowish and long (reaches the post-discal line) sex brand above the dorsum (in space 1b) on the forewing. In the hindwing, the post-discal line is slightly curved outward in spaces 4 and 5, and there is a dark brown indentation line stretching down to vein 1b.

Field Observations of Butterfly Behaviour:
The Long Brand Bush Brown is moderately common in Singapore with adults typically found flying low amongst grasses in the nature reserves, wasteland as well as urban parks and gardens. As with other Satyrinae members, the adults fly in an erratic and jerky manner as their wings are closed for a relatively long period during flights.

Early Stages:
Two local grass species, Ottochloa nodosa and Isachne globosa, have been recorded as larval hosts so far. The caterpillars feed on leaves of the host plant, and have been observed to forcefully ejecting their frass pellets, a larval habit rarely seen outside the skipper/flat families. They tend to rest lengthwise on the underside of a leaf during pauses between feeds.

Local host plant #1: Isachne globosa.

Local host plant #2: Ottochloa nodosa.

A mating pair of the Long Brand Bush Brown.

The eggs are laid singly on the underside of a grass blade. Each egg is more or less spherical (about 1mm in diameter) and translucent with a pale yellowish tinge. It appears to be smooth to the naked eyes, but faintly sculptured with a "fine" hexagonal reticulum when viewed with a macro lens.

Two views of an egg of the Long Brand Bush Brown.

Two views of a mature egg with the head clearly visible through the egg shell.

The egg takes about 3-3.5 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 3.5mm. The body is covered with dorso-lateral and lateral rows of moderately long 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, a few lateral protuberances.

Two views of a newly hatched caterpillar, length: 3.7.mm

As a result of its leaf diet, the 1st instar caterpillar soon takes on a strong greenish undertone. As growth proceeds, the dorsum of the last two to three segments turns reddish. The first instar lasts about 4 days with the body length increases to about 6.5mm.

Two views of a 1st instar caterpillar, length: 6.6mm.

Two views of a late 1st instar caterpillar, dormant prior to its moult.

In the 2nd instar, the cephalic horns become pointed and the two anal processes longer and thus pronounced. The few lateral conical protuberances on the head capsule are now much smaller and whitish in colour. The body color is pale yellowish with a green undertone. The head and body is also adorned with numerous minute tubercles, each with a single seta emanating from it. The 2nd instar lasts about 3 days with the body length reaches about 10-11mm.

Two views of a 2nd instar caterpillar, early in this stage.

Two views of a 2nd instar caterpillar, length: 9.5mm.

Two views of a late 2nd instar caterpillar, dormant prior to its moult, length: 11mm.

The 3rd instar caterpillar mostly resembles the previous instar. The head capsule is brown in the cephalic horns and the basal areas around the mouth parts but pale brown elsewhere. This stage takes 3-4 days to complete with body length reaching about 16-17mm.

Two views of a newly moulted 3nd instar caterpillar, length: 9mm.

Two views of a 3nd instar caterpillar, length: 17.2mm.

Two views of a late 3nd instar caterpillar, dormant prior to its moult.

The 4th instar caterpillar bears a close resemblance to the 3rd instar caterpillar initially with no obvious change of any features or markings. As growth progresses, the body base colour could change to either pale brown or pale yellowish green, with oblique and obscure stripes appearing laterally. Small reddish specks can be observed in these strips on the leading abdominal segments. The 4th instar lasts about 4-4.5 days with body length reaching 24-28mm.

Two views of a newly moulted 4th instar caterpillar, length: 17mm.

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: 26.5mm.

Two views of a late 4th instar caterpillar, dormant prior to its moult, length: 28mm.

The next moult brings the caterpillar to its 5th and final instar. So far only the brown colour form has been observed in three specimens bred over the past 2 years but it is likely that a yellow/green form exists too. Feature wise, the brown cephalic horns are now orange-coloured at the tip, and the oblique stripes on the body segments broader and more prominent. The red specks seen in the stripes in the earlier instar are now black and larger. Red coloration on the dorsum of posterior segments have completely vanished. In a period of 7-9 days, the body grows to a maximum length of about 38-39mm.

Two views of a newly moulted 5th instar caterpillar, length: 28mm.

Two views of a 5th instar caterpillar, length: 36mm.
Two views of a 5th instar caterpillar, late in this stage, body shortened and body colour changed to mostly green, length: 31mm.

Toward the end of the 5th instar, the body gradually shrinks in length and turn mostly green. Finally the caterpillar finds a spot on the underside of a leaf blade or a stem to spin a silk pad. It then secures itself there via its claspers at its anal end, and assumes its upside-down pre-pupatory pose.

A prep-pupa of the Long Brand Bush Brown.

After one day as a pre-pupa, pupation takes place. The smooth pupa is mostly green throughout. It is somewhat angular in appearance, with a dorsal keel on the thorax and ridges defining the dorsal wing margins. There are small, black specks dotting the wing pad and the ventral side of the abdomen. Dorso-lateral pairs of small and obscure yellowish spots can be observed on abdominal segments 2-6. Length of pupae: 16-17mm.

Three views of a pupa of the Long Brand Bush Brown.

After 5-5.5 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 emerges to start the next phase of its life cycle.

Three views of a mature pupa of the Long Brand Bush Brown.

A newly eclosed Long Brand Bush Brown.

  • [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 Nelson Ong, Loke PF, Tan Ben Jin, Federick Ho, Khew SK and Horace Tan

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