Butterfly of the Month - October 2024

Butterfly of the Month - October 2024

The Orange Tailed Awl (Bibasis sena uniformis)

A pristine Orange Tailed Awl puddling on a damp log

We move past the final quarter of the year, and the month of October 2024 is almost over. The bird migratory season is in full swing, and the birder community in Singapore is having a busy time out in the field looking out for rarities that may have made their way over Singapore skies at this time of the year. The annual migration usually lasts over six months, ending some time in March or April the year after.

Over the years, Singapore's green cover has, surprisingly, increased, making the island a relatively conducive place for biodiversity to thrive.  Despite its highly developed built environment, the city's urban planning has taken into consideration the flora and fauna that co-exist with us. Whilst some activists continue to lament the removal of mature trees and the sacrifice of wild green areas for development, our city-state has to a large extent, been able to manage land use to allow nature and the built environment to co-exist in harmony.

Whilst it is always a compromise to accept our wild free-ranging fauna to share human habitats, Singapore has, in recent years has attracted a myriad of biodiversity that was not as prevalent in the previous decades. Today, residents accept (or tolerate?) hornbills, otters, jungle fowls, wild boars, civet cats and many other animals to share our urban spaces with us. No one bats an eyelid at the family of jungle fowls with their chicks in tow, foraging in the grasslands of our HDB gardens - a scene that was very rare in the 80's and 90's.

An Orange Tailed Awl puddling at a sandy streambank

With a tagline of a "City In Nature", was this by design or by coincidence? Can an urbanised city such as Singapore learn how to design its urban development around nature, instead of excluding it? We see more butterflies in our urban parks and gardens that have been curated to attract these flying jewels and their caterpillars. The landscape plantings in our urban greenery are no longer designed with pristine, regimented and aesthetic priorities in mind - they have been curated with more native planting and flora that attract and enhances the survival of our biodiversity in the city.

And over to our Butterfly of the Month for October 2024 - a relatively rare butterfly that has been classified as "Near Threatened" in the Singapore Red Data Book 3rd Edition. This Hesperiidae, the Orange Tailed Awl (Bibasis sena uniformis) was recorded as a newly discovered species for Singapore some time in the early 2000's when an individual was spotted in the Central Catchment Nature Reserves. A rarity back in those days, its caterpillars were subsequently found breeding in numbers at the Singapore Botanic Gardens!

Orange Tailed Awls feeding at flowering Leea bushes - Top : Red Tree Shrub (Leea rubra) and Bottom : Bandicoot Berry (Leea indica)

The species has been observed across the island, at Dairy Farm Nature Park, Upper Seletar Reservoir Park, Upper Peirce Reservoir Park and at some urban parks and gardens. Its caterpillar host plant, Hiptage benghalensis (Malpighiaceae), is not rare, but can be found in cultivated areas around the island. Adult individuals have been spotted feeding at flowering plants in the early morning hours and closer to dusk.

The Orange Tailed Awl is dark brown above and unmarked. The wings are long and sharp with hindwing tornal cilia a deep orange-yellow that is very obvious in pristine individuals. Males and females are almost indistinguishable. The underside has a broad shining white discal band on both wings and the wings have a slight purple-blue sheen.

The hairy legs of the butterfly take on the orange-yellow colouration of the hindwing cilia and the robust thorax and abdomen of the butterfly is covered with greenish-grey hue hairs. The large eyes of the butterfly are typical of the family Hesperiidae. whilst the antennae are dark brown and unmarked.

An Orange Tailed Awl perched upside down on a leaf in the warmer hours of the day

The Orange Tailed Awl has a habit of hiding under a leaf with its wings folded upright during the warmer hours of the day. It has a darting skittish flight and is hard to photograph except when feeding at flowering plants. Males are often encountered puddling at sandy streambanks and muddy footpaths in the nature reserves.

Text by Khew SK : Photos by Alan Ang, David Chan, David Ho, Khew SK, Loke PF, Bobby Mun, Nelson Ong and Horace Tan 

Life History of the Mutal Oakblue

Life History of the Mutal Oakblue (Arhopala muta maranda)

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:

• [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.

Text by Horace Tan, Photos by Ash Foo, SK Khew, Lumin Ong, Tan Ben Jin and Horace Tan.

Butterfly of the Month - September 2024

Butterfly of the Month - September 2024

The Bigg's Brownwing (Miletus biggsii biggsii)

A mating pair of Bigg's Brownwings amongst ants and coccids

The month of September usually brings on the Southwest monsoon squalls - strong winds blowing from the southwest of Singapore.  These winds are also often called the "Sumatras". A Sumatra squall has characteristics that are specific to this region - it is a line of thunderstorms that develops over Indonesia's Sumatra island or the Strait of Malacca, then moves eastwards to affect Singapore and Peninsula Malaysia. On 17 September, such a squall hit Singapore island with enough severity to topple large trees and break branches. Over 300 trees were affected in Singapore, caused by strong winds that exceeded 80km/h.

Over in West Malaysia, which shares similar weather conditions of the Southwesterly monsoon winds, some fatalities were reported. In Penang, two unfortunate Chinese tourists were tragically killed when the winds blew down a tree that crushed the car that they were seated in. Elsewhere, in Pahang, a tree crushed an elderly man and injured his grand daughter at a site where they were camping. Another signal of climate change around the world where weather conditions exhibit more extreme outcomes?

September is also known for the celebration of the Mid-Autumn Festival that falls on the 15th day of the eighth lunar month. The full moon is considered a symbol of reunion, and is shining its brightest during this time. It is a month of delicious mooncakes and lantern parties where families delight in carrying lanterns at night, from traditional paper ones with wax candles to modern, battery-operated versions.

Our Butterfly of the Month for September 2024 is a representative of the sub-family Miletinae, often referred to as the "Harvesters". Our feature butterfly is the Bigg's Brownwing (Miletus biggsii biggsii). The common name of this species was Bigg's Brownie according to past literature, but has recently been changed to Brownwing to avoid the racially-sensitive word Brownie, sometimes misconstrued as a derogatory reference to dark-skinned people of certain races.

A Bigg's Brownwing in a sea of ants and not fearing for its life!

The Bigg's Brownwing usually flies in the shaded understorey of forested areas and patches of greenery around Singapore. They can be found in the nature reserves as well as urban parks and gardens. In particular the adult butterflies are often seen where their primary food source - several species of aphids and coccids are found. These insects are often "farmed" by ants.

The butterfly have a weak erratic flight and often remain in flight for long periods of time without taking a rest.  Occasionally, they are spotted feeding on the sugary excretions of the aphids and coccids in the company of the ant farmers. Despite the ferocious ants guarding their source of food, the Bigg's Brownwing can alight on a group of ants and yet remain "invisible" to the ants such that the ants leave the butterfly unharmed.

A fluttering Bigg's Brownwing showing a glimpse of its upperside

The Bigg's Brownwing is light brown above with an oblique white band across the forewing - wider in the female than the male. Very often, this white band is reduced and obscure, and in some individuals, absent altogether. The underside of the butterfly is light-greyish brown with dark markings that gives the flat wings a 3-dimensional effect. There is a series of black submarginal spots on both wings and where the marginal edges of the wings take on a deeper orange shading.

Many photos of this species depict the butterfly in a sea of ants. Whereas other species of butterflies daring enough to do this would be torn to pieces by the ants and eaten, the Bigg's Brownwing somehow always remains unmolested and where the ants do not percieve it as a threat nor as food! The butterfly lays its eggs amongst the aphids or coccids and the caterpillars that hatch eat these insects as its source of food, making the species in the sub-family Miletinae "carnivorous".

Text by Khew SK : Photos by David Chan, Ash Foo, Khew SK, Michael Khor, Koh CH, Loke PF, Bene Tay and Mark Wong