Butterfly Biodata:
Genus: Arhopala Boisduval, 1832
Species: muta Hewitson, 1862
Subspecies: maranda Corbet, 1941
Wingspan of Adult Butterfly: 17-19mm
Caterpillar Local Host Plant: Lithocarpus bennettii (Fagaceae, common names: Bennett’s Oak, Mempening Bagan, Parang-Parang Sulpho).
A female Mutal Oakblue.
A male Mutal Oakblue.
Physical Description of Adult Butterfly:
The Mutal Oakblue is a tailless species. On the upperside, the male is shining blue with narrow black borders. The female is shining blue with a purple tinge and has broad black borders. On the underside, both sexes are brown with the post-discal spots more squarish, resulting in a somewhat banded appearance. Spots 2 and 3 are partially dislocated between them in the forewing. In the hindwing, small black marginal spots with embedded blue scales are present in space 1b and upper end of space 1a.
A female Mutal Oakblue.
Field Observations:
The Mutal Oakblue is relatively rare in Singapore. Its occurrence is restricted to a small forested area in the central catchment reserve where its host plant is present. When encountered, its relatively small size compared to other Arhopala is a good indication of its presence.
A female Mutal Oakblue.
Another female Mutal Oakblue.
Early Stages:
Thus far, only one plant, Lithocarpus bennettii, has been recorded as the larval host plant in Singapore. The caterpillars of the Mutal Oakblue feed on young and immature leaves of this plant, and stay hidden in folded leaf shelter between feeds. The caterpillars have been found to be attended by ants in field observations.
Host plant: Lithocarpus bennettii (Bennett’s Oak).
The mother butterfly oviposits singly on the leaf or leaf bud of he host plant. Each egg is about 0.8mm in basal diameter, and whitish with a strong greenish undertone when freshly laid. It has a doom shape and a slightly depressed micropylar at the center of the top surface. The egg surface is reticulated with a moderately dense pattern of straight ridges and rounded protrusions.
Close-up views of an egg of the Mutal Oakblue. Basal diameter: 0.8mm.
Left: Hatching time! A caterpillar about to emerge from the mature egg. Right: empty egg shell left behind.
It takes about 3 days for the egg to hatch. The caterpillar nibbles away the top portion of the egg shell to emerge but does not bother to completely devour the remaining egg shell. The newly hatched has a pale yellowish body with a length of about 1.5mm. Its head is similarly coloured. The body also features long setae (hair) dorso-laterally and along the body fringe. These young caterpillars feed on the surface of the young leaf of the host plant. The body develops faint whitish marks dorsally and dorso-laterally as the growth progresses. After about 3 days of growth in the first instar, and reaching a length of about 2.9mm, the caterpillar moults to the next instar.
Two views of an early 1st instar caterpillar of the Mutal Oakblue, length: 1.5mm.
Two views of a 1st instar caterpillar of the Mutal Oakblue, length: 2.8mm.
Top: a late 1st instar caterpillar, dormant prior to its moult, length: 2.9mm. Bottom: a newly moulted 2nd instar caterpillar, length: 3mm.
In the 2nd instar, the yellowish brown to pinkish brown caterpillar features dorsal bands consisting of whitish rectangular marks, as well as spiracles embedded in round whitish marks. At this stage, the dorsal nectary organ on the 7th abdominal segment and the tentacular organs on the 8th abdominal segment are present but are rather inconspicuous. The 2nd instar caterpillar reaches up to a length of about 4.5mm, and after about 4 days in this stage, it moults again.
Two views of a 2nd instar caterpillar of the Mutal Oakblue, early in this stage, length: 3.6mm.
Two views of a 2nd instar caterpillar of the Mutal Oakblue, length: 4.2mm.
A late 2nd instar caterpillar of the Mutal Oakblue, dormant prior to its moult.
The 3rd instar caterpillar has a close resemblance to the 2nd instar caterpillar but with more numerous whitish speckles covering its body surface. the dorsum typically bears a darker shade of colours (reddish or greenish) than the body ground colour. The dorsal nectary organ and the pair of tentacular organs are now readily observed. The 3rd instar takes about 5 days to complete with the body length reaching about 7mm.
Two views of a 3rd instar caterpillar, early in this stage, length: 5.3mm.
A 3rd instar caterpillar being attended by two ants.
late 3rd instar caterpillar, dormant prior to its moult.
In the 4th instar, the caterpillar has its body ground colour featured in varying degrees of pale yellow and beige colours. The dorsal bands are whitish to yellowish green and has a more diffuse appearance than in the previous instars. The spiracles are pale yellowish brown. The dorsal nectary organ and the tentacular organs are also prominent in this penultimate instar. The 4th instar takes about 6-8 days to complete with the body length reaching about 10mm.
A newly moulted 4th instar caterpillar of the Mutal Oakblue. Length: 7mm.
Two views of a 4th instar caterpillar of the Mutal Oakblue. Top: 7mm; Bottom: 10mm.
A late 4th instar caterpillar, dormant prior to its next moult.
The 5th (final) instar caterpillar resembles the 4th instar caterpillar closely. The component markings within the dorsal bands in the previous instars have largely fused together to form a very broad dorsal band with ill-defined boundaries. The spiracles are more prominent with darker yellowish brown to orangy brown colours.
A newly moulted 5th instar caterpillar of the Mutal Oakblue eating its exuvia.
Two views of a 5th instar caterpillar of the Mutal Oakblue. Length: 12.5mm.
A leaf shelter of a final instar caterpillar of the Mutal Oakblue.
Two views of a 5th instar caterpillar of the Mutal Oakblue. Length: 16mm.
Two views of a late 5th instar caterpillar of the Mutal Oakblue. Length: 16mm.
After about 13-16 days of feeding in the 5th instar and reaching a length of up to about 15-16m, the caterpillar stops food intake and seeks out a pupation site in a leaf shelter. During this time, its body gradually shrinks and turns almost uniformly pale beige brown. The pre-pupatory caterpillar prepares for pupation by spinning a silk girdle and a silk pad to which it attaches itself via anal claspers.
Pre-pupa of the Mutal Oakblue. Top: early pre-pupa. Bottom: late pre-pupa.
After about one and a half day as a pre-pupa, pupation takes place. Compared to pupa of other lycaenid species, the pupa of the Mutal Oakblue is broader in shape and has a rather flat abdomen. The pupa is pale yellow brown in the abdomen and pale greyish brown in the thorax and wing pads. Small black speckles adorn the pupal surface. Pupal length: 10mm.
Two views of a pupa of the Mutal Oakblue.
About 8-9 days later, the pupa turns dark, first in the wing pad and thorax, then progressively in the abdomen. The extent of the bluish patch in the wing pads gives an early indication of the gender of the soon-to-emerge adult. The next day, the pupal stage comes to an end with the emergence of the adult butterfly.
Two views of a mature pupa of a female Mutal Oakblue.
Two views of a mature pupa of a male Mutal Oakblue.
A newly eclosed female Mutal Oakblue resting near its pupal case.
A newly eclosed male Mutal Oakblue resting near its pupal case.
References:
Genus: Arhopala Boisduval, 1832
Species: muta Hewitson, 1862
Subspecies: maranda Corbet, 1941
Wingspan of Adult Butterfly: 17-19mm
Caterpillar Local Host Plant: Lithocarpus bennettii (Fagaceae, common names: Bennett’s Oak, Mempening Bagan, Parang-Parang Sulpho).
Physical Description of Adult Butterfly:
The Mutal Oakblue is a tailless species. On the upperside, the male is shining blue with narrow black borders. The female is shining blue with a purple tinge and has broad black borders. On the underside, both sexes are brown with the post-discal spots more squarish, resulting in a somewhat banded appearance. Spots 2 and 3 are partially dislocated between them in the forewing. In the hindwing, small black marginal spots with embedded blue scales are present in space 1b and upper end of space 1a.
Field Observations:
The Mutal Oakblue is relatively rare in Singapore. Its occurrence is restricted to a small forested area in the central catchment reserve where its host plant is present. When encountered, its relatively small size compared to other Arhopala is a good indication of its presence.
Early Stages:
Thus far, only one plant, Lithocarpus bennettii, has been recorded as the larval host plant in Singapore. The caterpillars of the Mutal Oakblue feed on young and immature leaves of this plant, and stay hidden in folded leaf shelter between feeds. The caterpillars have been found to be attended by ants in field observations.
The mother butterfly oviposits singly on the leaf or leaf bud of he host plant. Each egg is about 0.8mm in basal diameter, and whitish with a strong greenish undertone when freshly laid. It has a doom shape and a slightly depressed micropylar at the center of the top surface. The egg surface is reticulated with a moderately dense pattern of straight ridges and rounded protrusions.
It takes about 3 days for the egg to hatch. The caterpillar nibbles away the top portion of the egg shell to emerge but does not bother to completely devour the remaining egg shell. The newly hatched has a pale yellowish body with a length of about 1.5mm. Its head is similarly coloured. The body also features long setae (hair) dorso-laterally and along the body fringe. These young caterpillars feed on the surface of the young leaf of the host plant. The body develops faint whitish marks dorsally and dorso-laterally as the growth progresses. After about 3 days of growth in the first instar, and reaching a length of about 2.9mm, the caterpillar moults to the next instar.
In the 2nd instar, the yellowish brown to pinkish brown caterpillar features dorsal bands consisting of whitish rectangular marks, as well as spiracles embedded in round whitish marks. At this stage, the dorsal nectary organ on the 7th abdominal segment and the tentacular organs on the 8th abdominal segment are present but are rather inconspicuous. The 2nd instar caterpillar reaches up to a length of about 4.5mm, and after about 4 days in this stage, it moults again.
The 3rd instar caterpillar has a close resemblance to the 2nd instar caterpillar but with more numerous whitish speckles covering its body surface. the dorsum typically bears a darker shade of colours (reddish or greenish) than the body ground colour. The dorsal nectary organ and the pair of tentacular organs are now readily observed. The 3rd instar takes about 5 days to complete with the body length reaching about 7mm.
In the 4th instar, the caterpillar has its body ground colour featured in varying degrees of pale yellow and beige colours. The dorsal bands are whitish to yellowish green and has a more diffuse appearance than in the previous instars. The spiracles are pale yellowish brown. The dorsal nectary organ and the tentacular organs are also prominent in this penultimate instar. The 4th instar takes about 6-8 days to complete with the body length reaching about 10mm.
The 5th (final) instar caterpillar resembles the 4th instar caterpillar closely. The component markings within the dorsal bands in the previous instars have largely fused together to form a very broad dorsal band with ill-defined boundaries. The spiracles are more prominent with darker yellowish brown to orangy brown colours.
After about 13-16 days of feeding in the 5th instar and reaching a length of up to about 15-16m, the caterpillar stops food intake and seeks out a pupation site in a leaf shelter. During this time, its body gradually shrinks and turns almost uniformly pale beige brown. The pre-pupatory caterpillar prepares for pupation by spinning a silk girdle and a silk pad to which it attaches itself via anal claspers.
After about one and a half day as a pre-pupa, pupation takes place. Compared to pupa of other lycaenid species, the pupa of the Mutal Oakblue is broader in shape and has a rather flat abdomen. The pupa is pale yellow brown in the abdomen and pale greyish brown in the thorax and wing pads. Small black speckles adorn the pupal surface. Pupal length: 10mm.
About 8-9 days later, the pupa turns dark, first in the wing pad and thorax, then progressively in the abdomen. The extent of the bluish patch in the wing pads gives an early indication of the gender of the soon-to-emerge adult. The next day, the pupal stage comes to an end with the emergence of the adult butterfly.
References:
- [C&P5] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, G. and N. van der Poorten (Eds.), 5th Edition, Malayan Nature Society, 2020.
- Butterflies of Thailand, Pisuth Ek-Amnuay, 2nd Edition, 2012.
- A Field Guide to the Butterflies of Singapore, Khew S.K., Ink On Paper Communications, 2nd Edition, 2015.
