Butterfly of the Month - April 2025

Butterfly of the Month - April 2025

The Yellow Streak Darter (Salanoemia tavoyana)

A Yellow Streak Darter resting on a frond of a fern

We have passed the first quarter of the year and the world has become a lot more volatile and chaotic as we move into the 2nd quarter. Over in the USA and the rest of the world, 'tariff' has become the most searched-for word on the internet. After the US President rolled out his Liberation Day measures, the economic world suffered a nasty shock as billions were wiped off the stock markets around the world. And as if riding a roller coaster, the markets reacted violently to policy reversals - up and down, in just a matter of days.

A Yellow Streak Darter sipping nectar from the flower of the Singapore Daisy

And it's not something that is going to be over quickly as a new normal will begin to change how the world moves on from this. The trade war's victims will probably be the average man-in-the-street who will have to struggle with an even higher cost of living to cover daily essentials and necessities. It is amazing how global equilibrium can be disrupted so easily by one man and in so short a time without resorting to any violence or hostilities... yet.

Over in Singapore, election fever has gripped the population, as Nomination Day and Polling Day have been confirmed for 23 April and 3 May respectively. In an already chaotic world, how will the incumbent political party fare with the citizenry? Will the ruling party wrest back constituencies that it lost in the previous election? Or will it lose even more ground to an already strengthening opposition presence? The electorate will decide in a couple of weeks' time.

April 2025 is an unusually wet month for the region, with storm surges causing flash floods in Malaysia and Singapore. Commensurately, butterfly activity has also been lacklustre and low. The wet and cooler weather seems to have put a dampener on the numbers of butterflies out and about in our favourite butterfly hunting locations all around the island.

A Yellow Streak Darter perched on a leaf of its caterpillar host plant, the Mangrove Fan Palm

This month, we feature yet another "exotic" or non-native species that was a new discovery for Singapore when it was first observed and recorded in Feb 2011 on the offshore island of Pulau Ubin - the Yellow Streak Darter (Salanoemia tavoyana). First observed at a heavily shaded area near the Sensory Trail on Pulau Ubin, it has since been spotted elsewhere on Ubin at other locations where the caterpillar host plant, Licuala spinosa (Mangrove Fan Palm) grows. The host plant is not rare and is found on Singapore island where it is often used as a landscaping plant in many parks, gardens and roadside greenery.

The first field shot of this species taken in Singapore in Feb 2011

The species was described as "known only from South Burma, Kedah and Langkawi", so it's a mystery as to how it appeared in Singapore! After its discovery, it has continued to be regularly seen on Pulau Ubin, although observations of its caterpillars far outnumber observations of the adult butterflies.  The unique eating pattern of the caterpillars and the construction of leaf shelters make them easy to spot on the Mangrove Fan Palm that grows all around the island.

A Yellow Streak Darter shot in its typical environment in deep shaded forested habitat

The upperside of the Yellow Streak Darter is brown with a series of hyaline yellow spots and streaks.  There is a prominent yellow streak on the basal half of the forewing. There are two yellow cell spots which are the diagnostic feature of this species. The antennae are yellow just below the apiculus with the shaft banded with yellow and brown. The eyes are a solid dark brown and large.

The underside is a rich yellow with dark spots and a characteristically obviously yellow-centred cell spot. The marginal areas of both wings are a deeper orange-yellow.  The abdomen is chequered with yellow and brown with the legs a solid orange-yellow and unmarked. The wingspan of the adult ranges from 29-32mm.

Yellow Palm Dart adults are usually observed perched on the uppersides of foliage in heavily shaded forested areas where they frequent. When disturbed, they fly off rapidly in the usual Skipper-like fashion. This species' field behaviour is reminiscent of related species like the Yellow Chequered Lancer and Chequered Lancer. The complete life history has been recorded on this blog here.

Text by Khew SK : Photos by Khew SK, Koh CH, Richard Ong, Michael Soh, Simon Sng, Horace Tan and Zick Soh.

Further Reading : 

• Life History of the Yellow Streak Darter

Life History of the Dark Grass Brown

Life History of the Dark Grass Brown (Orsotriaena medus cinerea)

Butterfly Biodata:
Genus: Orsotriaena Wallengren, 1858
Species: medus Fabricius, 1775
Subspecies: cinerea Butler, 1867
Wingspan of Adult Butterfly: 21-22mm
Caterpillar Local Host Plants: Axonopus compressus (Poaceae, common names: Wide-leaved Carpet Grass, Cow Grass), Urochloa maxima (Poaceae, common name: Guinea Grass), Ischaemum ciliare (Poaceae, common names: Smut Grass).

Physical Description of Adult Butterfly:
On the upperside, the wings are dark brown and unmarked. On the underside, both wings are dark brown in ground colour and have a clear-whitish stripe extending from the costa on the forewing to the tornus on the hindwing. There are two large submarginal ocelli (eye-spots) on the forewing, and three more (two large, one small) in the hindwing.

Field Observations of Butterfly Behaviour:
The Dark Grass Brown is a common butterfly in Singapore. Adults prefer shaded habitats and can be sighted flying low, in and around grassy patches at multiple locations on the fringe of the nature reserves, nature parks and catchment areas.

Early Stages:
The caterpillars of the Dark Grass Brown feed on various grass species in its distribution region around the globe. In Singapore, three grass species, Ischaemum ciliare, Urochloa maxima and Axonopus compressus, have been recorded as larval hosts. The caterpillars feed on grass blades of the host plant, and have been observed to forcefully ejecting their frass pellets, just like their Mycalesis (Bush Brown) cousins. They tend to rest on the underside of a leaf during pauses between feeds.

Local host plant #1: Axonopus compressus.

Local host plant #2: Urochloa maxima.

Local host plant #3: Ischaemum ciliare.

A mating pair of the Dark Grass Brown.

The eggs are laid singly on the underside of a grass blade. Each oblate ellipsoidal egg (about 1.1mm in diameter and 1mm in height) is pale whitish. The surface appears smooth to the naked eyes, but is actually sculptured with numerous tiny indentations/pits when viewed with a macro lens.

A mother Dark Grass Brown laying an egg on the underside of a grass blade.

Two views of an egg of the Dark Grass Brown.

The egg takes about 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 2.9mm. The body is covered with dorso-lateral and lateral rows of whitish setae. At the posterior end, there is a pair of backward-pointing processes. Its pale-yellowish head has pale brown markings, a number of dark setae, a pair of short and rounded horns and a few lateral protuberances.

Two views of a mature egg of the Dark Grass Brown.

Two views of a newly hatched caterpillar of the Dark Grass Brown .

As a result of its leaf diet, the 1st instar caterpillar soon takes on a greenish undertone and its body lengthens gradually. The first instar lasts about 3-3.5 days with the body length increases to about 6.5mm.

Two views of a 1st instar caterpillar of the Dark Grass Brown after a few meals of grass lamina, length: 3.2mm.

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

In the 2nd instar, both the cephalic horns and anal processes become proportionately longer and pointed, and reddish brown in colour. The few lateral conical protuberances on the head capsule are now much smaller and whitish in colour. The body is pale yellowish green. The head and body is also adorned with numerous minute tubercles, each with a short seta emanating from it. The 2nd instar lasts about 3-3.5 days with the body length reaches about 11.5mm.

Two views of a 2nd instar caterpillar of the Dark Grass Brown, early in this stage.

Two views of a 2nd instar caterpillar of the Dark Grass Brown, length: 10.8mm.

Two views of a late 2nd instar caterpillar of the Dark Grass Brown , dormant prior to its moult, length: 11.5mm.

The 3rd instar caterpillar mostly resembles the 2nd instar caterpillar. One visible difference is that the cephalic horns are proportionately longer than in those in the 2nd instar. This stage also takes 3-4 days to complete with body length reaching about 19.5mm (not including the length of the cephalic horns and anal processes).

Two views of 3nd instar caterpillar of the Dark Grass Brown, early in this stage, length: 12mm.

Two views of a 3nd instar caterpillar of the Dark Grass Brown, length: 17mm.

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

The 4th (and final) instar caterpillar bears a close resemblance to the 3rd instar caterpillar in most body features and markings. The cephalic horns are again proportionately longer than those in the previous instar, and are now dark reddish brown in color. Dorso-laterally, indistinct pale yellowish bands run lengthwise. subspiracularly a whitish band also run lengthwise along the body fringe. In some specimens, a narrow reddish band also appears above the whitish band. In a period of about 5-7 days, the body grows to a maximum length of about 32-34mm (not including the length of the cephalic horns and anal processes).

Two views of a newly moulted 4th instar caterpillar of the Dark Grass Brown, length: 19mm.

Two views of a 4th instar caterpillar of the Dark Grass Brown with reddish lateral band, length: 28mm.

Two views of a 4th instar caterpillar of the Dark Grass Brown, length: 32mm.

Toward the end of the 4th instar, the body base colour turns pinkish, and a reddish dorsal band and two lateral bands become evident. In the last day, the body length shortened, and the caterpillar will seek out a spot on the side of a grass stem to spin a silk pad. It then anchors itself there via its anal end, and assumes its upside-down pre-pupatory pose.

Two views of a late 4th instar caterpillar of the Dark Grass Brown, still feeding, length: 36mm.

Two views of a late 4th instar caterpillar of the Dark Grass Brown, ceased feeding, and resting on its chosen pupation spot on a stem.

Two views of a late 4th caterpillar of the Dark Grass Brown releasing its grip to enter the dormant pre-pupal stage.

Two views of an early prep-pupa of the Dark Grass Brown.

After nearly one day as a pre-pupa, pupation takes place. The smooth pupa is mostly pale yellowish brown throughout with narrow pale brownish streaks and speckles. It is somewhat angular in appearance, with a small dorsal keel on the thorax and ridges defining the dorsal wing pad margins. The pupa has a pair of long cephalic horns which are tightly adjoined. It starts to take on a gold sheen about one day after pupation. Length of pupae: 19-20mm (including the length of the cephalic horns).


The pupation event of a Dark Grass Brown caterpillar.

Two views of a one-day-old pupa of the Dark Grass Brown.

Three views of a two-day-old pupa of the Dark Grass Brown.

Close-up view of a pupa of the Dark Grass Brown, showing the golden sheen.

After about 5.5 days of development, the pupa becomes darkened in color overall, and its wing pads totally blackened. Total pupal duration: 6.5 days. The next day the eclosion event takes place with the adult butterfly emerges to start the next phase of its life cycle.

Two views of a mature pupa of the Dark Grass Brown.


The eclosion event of a Dark Grass Brown.

A newly eclosed Dark Grass Brown resting on 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 Huang CJ, Khew SK, Loh Mei Yee, Loke PF and Horace Tan. Videos by Horace Tan.

Butterfly of the Month - March 2025

Butterfly of the Month - March 2025

The White Palm Bob (Suastus everyx everyx)

A White Palm Bob feeding on bird dropping 

We are at the end of the first quarter of the year, and the weather has gone wonky again. Severe floods hit the southern part of the Malay Peninsula in five districts in the state of Johor, where over 5,000 residents were evacuated to flood relief centres. The monsoon surges inundated Singapore too, but the years of upgrading drains, building underground reservoirs and enhancement of flood alleviation infrastructure managed to mitigate the severity of the floods that hit Johor. Yes, there were still some flash floods in Singapore, but those didn't last very long.

March is usually a warm humid month in Southeast Asia, but the weather has been atypically wet over the last two weeks of the month. And as if to remind the human race of Mother Nature's wrath, a 7.7 magnitude earthquake, with its epicentre near Mandalay, hit Myanmar, causing widespread damage and fatalities. A 33-story building under construction near the popular Chatuchak market in Bangkok, Thailand’s capital city, collapsed. Footage of the building’s demise shows crowds of onlookers running away from the rubble in panic.

The aftershock of the Myanmar earthquake could be felt in China and even as far south as Penang in Malaysia where tremors were reported. One wonders if these earthquakes and fault lines that are constantly shifting will one day reach Singapore, and what is needed to plan and design buildings for such an eventuality?

All over the world, the Muslim community celebrates Hari Raya Puasa on 31 Mar 2025, after a month of fasting in the month of Ramadan. Astronomical calculations indicate that the crescent moon for the Islamic month of Syawal appeared above Singapore’s horizon for 48 minutes following sunset on Sunday. The sighting of the crescent moon not only marks the beginning of Syawal but also signifies that Hari Raya Puasa, or Hari Raya Aidilfitri, will take place on 31 March.

Our Butterfly of the Month for March 2025 is the White Palm Bob (Suasus everyx everyx). Only recently discovered, the White Palm Bob is considered a new addition to the Singapore checklist, and hence considered "non-native". It is fast-flying, skittish and frequents the deep-shaded forested nature reserves of Singapore.  Described as "very rare" in Malaysia (ref C&P5 pp 315 and Plate 118 : 10), the White Palm Bob is quite regularly observed in Singapore and classified as "Near Threatened" in the Singapore Red Data Book 3rd Edition.

Dorsal view of a White Palm Bob

The White Palm Bob is dark brown above and unmarked except for a narrow whitened area at the tornus of the hindwing.  The underside of the hindwing is largely whitened and there is a dark greyish spot at the dorsal area of the hindwing. The hindwing cilia is whitened in pristine individuals.  The costal area of the underside of the hindwing appears speckled with white dots on a brownish base.

A White Palm Bob feeding on the flowers of the Red Tree Bush (Leea rubra)

A White Palm Bob feeding on the flower of a Spanish Needle (Bidens alba)

The butterfly usually lurks in shady forested areas where it can be spotted perched on the uppersides of leaves with its wings folded upright. It is also observed puddling at muddy footpaths, feeding on bird droppings and occasionally on the flowers of Leea rubra and Leea indica at forested edges.

A White Palm Bob pudding at a muddy forest trail

The species has been successfully bred in Singapore on Daemonorops augustifolia (Arecaceae) (Water Rattan Palm), a relatively common palm found in the nature reserves. It shares this host plant with at least two other skippers, the Tree Flitter (Hyarotis adrastus praba) and Quedara monteithi monteithi and both species can also be found in the same locations as the White Palm Bob.

Text by Khew SK : Photos by David Ho, Khew SK, Koh CH, Neo TP, Richard Ong, Michael Soh, Horace Tan, Mark Wong, Benjamin Yam and Angela Yeo.