11 July 2020

Singapore's Line Blues - Part 2

Singapore's Line Blues - Part 2
Featuring the Line Blue Butterflies of Singapore


A Two Spotted Line Blue perches for a rest

In this 2nd part of our blogpost featuring the butterfly species with the name "Line Blue" in their names, we take a look at the remaining 4 species that have been recorded as new discoveries to Singapore. Under the IUCN definitions, these species are therefore "non-native" or "exotic" to Singapore. These Line Blue butterflies species are typically small in size, skittish and erratic flyers.


A Banded Line Blue feeding on some moisture from a fern frond

Other than the Two Spotted Line Blue, which is common in Australia, the other "non-native" Line Blues can be found in neighbouring Malaysia. Although they were not recorded in the checklists of the early authors, there is always a likelihood that they may have been missed earlier and were extant in Singapore all this time. However, there is no way that this can be ascertained nor validated with certainty at this point in time, and these species are therefore treated as "exotics" unless other evidence surfaces to prove otherwise.



A Barred Line Blue (top) and a Dingy Line Blue (bottom) pudding at damp muddy footpaths

Of the species featured here, two are from the genus Prosotas which complement the two native species already found in Singapore. The other is a sole representative of the genus Petralaea that can be found in the region. Whilst these 3 species may be able to fly over from nearby Malaysia, the aforementioned Australian species, the Two Spotted Line Blue probably came over to Singapore as a stowaway on plants that have been imported as part of landscaping material.

4. The Dingy Line Blue (Petralaea dana)


A Dingy Line Blue puddling.  Note the characteristic tornal spots without any orange crown/ring and absence of tails on the hindwing

The Dingy Line Blue was first discovered in 2004 on the offshore island of Pulau Ubin. It was recorded as a new discovery for Singapore. Since then, the species has been observed on the main island of Singapore and is relatively widespread in distribution. It has been recorded from the mangrove areas on Pulau Ubin, to the urban hill park at Telok Blangah, and also in the heart of the Central Catchment Nature Reserve.


A Dingy Line Blue puddling on a brick footpath at an urban park

It is a skittish butterfly and flies erratically. It is more often observed when puddling at muddy footpaths and streambanks. With an average wingspan of 24-26mm, it is difficult to identify this species in flight, unless it stops to feed or rest.


A mating pair of Dingy Line Blue

The upperside of the male is a pale violet blue with narrow black margins, whilst the female is brown with a whitish patch on the forewing and metallic blue scaling at the wing bases of both wings. The underside is greyish brown and has pale white striations. There are two black spots on the underside of the tornal area of the hindwings. The species can be easily separated from its related lookalikes in that the tornal spots are not orange-crowned.

5. The Two Spotted Line Blue (Nacaduba biocellata)


A Two Spotted Line Blue feeding at a flower

The Two Spotted Line Blue was another new discovery for Singapore when the species was formally recorded in the Singapore Checklist in 2008. There were a few unconfirmed sightings of this species earlier, but could not be validated. It is widely distributed and can be found on the main island of Singapore, as well the offshore islands of Pulau Ubin and Pulau Semakau. The species is usually found in urban parks and gardens and is seasonal. When it occurs, many individuals are encountered, to the extent of being temporarily abundant. They then disappear as mysteriously as they appeared, until the next seasonal outbreak.



Two Spotted Line Blue perched whilst resting between long active flights

The species occurs in the South Pacific, and is common throughout Australia where it is a native species. Being a small butterfly with an average wingspan of 22-26mm, it is highly unlikely that it managed to migrate to Singapore on its own steam. Its caterpillar host plant is the invasive Australian Wattle (Acacia auriculiformis) and its life history has been recorded here.


A male Two Spotted Line Blue sunbathing with open wings

The males are blue on top, with diffused black margins on both wings. The females are a drab brown and unmarked. The underside is a pale brown with dark wavy striations across both wings. Both sexes have a pair of orange-ringed black eyespots at the tornal area, with light greenish iridescent scales within each eyespot.  These two eyespots are probably unique enough to give the species its English common name.

6. The Banded Line Blue (Prosotas lutea sivoka)


A Banded Line Blue perched to rest amongst some dead twigs

The Banded Line Blue was added to the Singapore Butterfly checklist in 2012 as a new discovery. A small colony was observed at the Bukit Brown Cemetery during a survey of the biodiversity in the area. The cemetery was slated for the development of a major arterial highway and parts of the land would be cleared for the road expansion. Interestingly, this small butterfly with an average wingspan of 22-24mm has eluded observation until recently. Also as interesting is that its caterpillar host plant, Acacia concinna is considered critically endangered, although several plants were found at the locality where the butterfly was observed.


A Banded Line Blue ovipositing on its caterpillar host plant, Soap Pod Tree (Acacia concinna)

The species flies erratically, almost reminiscent of the flight characteristics of its native cousins, the Tailless Line Blue and the Common Line Blue. It can fly restlessly for long periods of time, unless stopping to feed on flowers or to rest. It has also been observed to puddle at damp muddy footpaths.


A Banded Line Blue puddling along a muddy footpath

The upperside of the Banded Line Blue is brown and unmarked. The underside is a distinctively pale yellowish-brown with diffused darker striations across both wings.  There is a prominent marginal black spot at space 6 at the apical area of the hindwing. The tornal area has two small black spots and a larger sub-marginal one at space 2 of the hindwing. The species has no tails. The complete life history of the species has been recorded in Singapore and can be found on this blog here.

7. The Barred Line Blue (Prosotas aluta nanda)


A Barred Line Blue puddling at a sandy streambank in the nature reserves

The Barred Line Blue has many lookalikes in related genera like the Nacaduba, Ionolyce and Jamides. It may be why this species has eluded observers and the early authors. Only after close observations and validation that this species was added to the Singapore Butterfly checklist in 2014. However, upon scrutiny of earlier photographic records, it was already photographed, but incorrectly identified, from as early as 2008.



Where it has been observed, it has most often been encountered whilst puddling at sandy streambanks within the forested nature reserves. It is unlikely that this species can be found in urban parks and gardens, and is a forest-dependent species in Singapore. It is skittish in flight, not unlike the Nacaduba species, but can easily be approached when it is puddling.


A Barred Line Blue perched on a blade of grass

The male is blue on the upperside, whilst the female is brown with a bluish-green patch on the forewing. The key diagnostic feature of the Barred Line Blue is the post-discal striation in space 3 on the underside of the forewing. This striae is shifted slightly towards the base of the forewing as compared to the adjacent striae in space 4. The hindwing has a white-tipped black filamentous tail at vein 2 and there is a large orange-crowned black eyespot at the tornal area of the hindwing. The early stages of this species is currently unknown.

Text by Khew SK : Photos by James Chia, Huang CJ, Khew SK, Koh CH, Loh MY, Loke PF, Michael Soh and Jonathan Soong

Further reading



04 July 2020

Singapore's Line Blues - Part 1

Singapore's Line Blues - Part 1
Featuring the Line Blue Butterflies of Singapore


A male Common Line Blue puddling at a sandy streambank

The "Line Blue" butterflies are a group of rather small species that belong to the subfamily Polyommatinae of the family Lycaenidae. The Polyommatinae are often referred to as the "Blues". A large number of the species in this subfamily are small and delicate butterflies with many of them sporting thin filamentous white-tipped tails on their hindwings. Many species, particularly the males, have blue uppersides, hence the English common name for the group.


A Pointed Line Blue perched on top of a leaf

This blogpost introduces the seven extant species found in Singapore that carry the English common name "Line Blue" in their names. All these species feature a series of striations across the undersides of both the fore- and hindwings. They have the typical "eyespot" at the tornal area of the hindwing and, in some of the species, coupled with the thin tails, form a decoy to fool predators into attacking a less critical part of their wings.


A Tailless Line Blue feeding on the flower of the Stringbush

In this article, we introduce three of the seven species that are found in Singapore. Ironically, of these "Line Blues" found in Singapore, four are new discoveries. Based on reference literature, these four were not recorded in Singapore by the early authors. We will feature these four "exotics" in Part 2 of the article next weekend. We will now highlight the three native, and relatively common species in Singapore.

1. The Pointed Line Blue (Ionolyce helicon merguia)


A puddling Pointed Line Blue

The Pointed Line Blue is the sole representative of the genus Ionolyce in the region. It is relatively common and widespread in distribution across the island. It can be found in urban parks and gardens, and sometimes in the forested nature reserves as well. Males are regularly found puddling at damp streambanks and muddy footpaths, and are partial to human perspiration as well.



It is a fast flyer, and flies erratically, and is often skittish, until it comes down to puddle on the forest floor. Once it is a feeding mood, it can also be coaxed to feed on a sweaty finger. The forewings of the males are more pronounced and pointed than other lookalike species in the subfamily.


A male Pointed Line Blue opens its wings to sunbathe

The male Pointed Line Blue is a deep purple-blue on top, with a very thin black margin and unmarked. The female is predominantly brown on her uppersides with the discal areas and wing bases overlaid with bluish-purple. The undersides are dull greyish-brown with narrow whitish wavy lines across both wings. There is an orange-crowned eye spot at the tornal area of the hindwing and a black filamentous tail which is tipped with white at vein 2 of the hindwing.

2. The Common Line Blue (Prosotas nora superdates)


A Common Line Blue feeding on the Spanish Needle flower

The Common Line Blue is a small butterfly that has a wingspan of around 25-28mm and considered moderately common. It can be found in urban parks and gardens but can also be found in the forested nature reserves. Males of the Common Line Blue are attracted to damp footpaths and streambanks where they come down to puddle for salts.


A male Common Line Blue puddling with its wings opened

The male Common Line Blue is bluish-purple on the upper surfaces with a thin black border, whilst the upperside of the female is dark brown and unmarked.  The underside of the male appears orangey whilst the base colour of the female is greyish buff.


A mating pair of Common Line Blue.  Left : Male Right : Female

The underside features white-edged dark lines across both wings with the interstitial spaces orange in the males, and grey with orange speckles in the female. There is a large orange crowned black eyespot at the tornal area of the hindwing below, with iridescent greenish scales. At vein 2 of the hindwing is a filamentous white-tipped tail.

3. The Tailless Line Blue (Prosotas dubiosa lumpura)


A Tailless Line Blue puddling

The Tailless Line Blue is a closely related species from the same genus as the Common Line Blue. But as its name suggests, there is no tail on the hindwing of this species. It is common, and sometimes seasonally abundant where two dozen individuals or even more, can be observed, frolicking amongst the shrubbery.


A male Tailless Line Blue opens its wings to sunbathe

The male Tailless Line Blue is bluish-purple on top with an almost imperceptible border. The female is brown on the uppersides with a blue discal patch. The underside is greyish, with the usual white-edged dark lines across both wings. There is a large tornal spot on the underside of the hindwing with some iridescent pale green scales.


A mating pair of Tailless Line Blues

Males are sometimes found puddling at damp footpaths, drains and wet areas. Females are more often found at flowering plants like the Stringbush. The species is widely distributed and is common throughout Singapore in urban parks and gardens.

Text and Photos by Khew SK

28 June 2020

Life History of the Ciliate Blue

Life History of the Ciliate Blue (Anthene emolus goberus)


Butterfly Biodata:
Genus: Anthene Doubleday, 1847
Species: emolus Godart, 1824
Subspecies: goberus Fruhstorfer, 1916
Wingspan of Adult Butterfly: 24-30mm
Caterpillar Local Host Plants: Saraca thaipingensiss (Fabaceae, common name: Yellow Saraca), Saraca indica (Fabaceae, common name: Ashoka Tree), Bauhinia sp. (Fabaceae), Smilax setosa (Smilacaceae, common name: Sarsaparilla Vine), Senna fistula (Fabaceae, common name: Golden Shower), Senna alata (Fabaceae, common name: Candle Bush), Syzygium zeylanicum (Myrtaceae).



A female Ciliate Blue.

A male Ciliate Blue.

Physical Description of Adult Butterfly:
On the upperside, the male is dark purplish blue with narrow black borders. The female is brown, paler at discal areas and is iridescent blue at the basal areas of the both fore- and hindwings. On the underside, both sexes are pale greyish brown with a series of white striations on both wings. On the hindwing underside, there is a prominent black spot on the dorsum, an orange-crowned tornal spot in space 2. Also on the hindwing, there are short fine tails at the end of veins 1b, 2 and 3. These fine tails are an extension of the cilia. The tail at the end of vein 3 is the shortest of the three and  barely noticeable.

Short fine tails at the end of veins 1b, 2 and 3.




Field Observations:
Ciliate Blue is common in Singapore. It is essentially an urban butterfly, but can occasionally be found in forested areas. Adults have been observed flowers for their carbohydrate intake. Males are often encountered puddling on damp footpaths, and is partial to human perspiration. The adults have a rapid and erratic flight, but tend to fly short distances if not unduly alarmed.




Early Stages:
The caterpillar of the Ciliate Blue is polyphagous, and is known to utilize multiple plants  in a number of families as larval food plant in its range of distribution across the region. Locally in Singapore, we have recorded seven plants to date. The most popular of these is the Yellow Saraca from Fabaceae. Other plants are Saraca indica (Fabaceae), Senna fistula (Fabaceae), Senna alata (Fabaceae), Smilax setosa (Smilacaceae), Syzygium zeylanicum (Myrtaceae) and one Bauhinia sp. (Fabaceae). The caterpillars feed on young and immature leaves of these plants.

Host plant #1: Saraca thaipingensiss (Yellow Saraca).

Host plant #2: Saraca indica.

Host plant #3: Syzygium zeylanicum.

The caterpillar of the Ciliate Blue has a close obligate myrmecophilous relationship with the weaver ant (Oecophylla smaragdina). In the wild, the caterpillars of the Ciliate Blue invariably appear in the company of the weaver ants (primary worker ants). The attending ants are attracted to the lycaenid larvae by the carbohydrate-rich secretions released by the caterpillar, and their presence offer protection to the caterpillar from parasitoids and predators. As with other lycaenid caterpillars, the caterpillar of the Ciliate Blue has pore cupola organs (specialized epidermal glands on its body surface) which can release appeasement substances to suppress the ant aggressiveness towards it.

A weaver ant attending to a final instar caterpillar of the Ciliate Blue. A droplet can be seen secreted from the dorsal nectary organ.


Besides featuring pictures of the immature stages of the Ciliate Blue in the wild, this life history article also documents the full development of a large number of Ciliate Blue caterpillars from the egg stage to the adult stage, without any attending weaver ants in an indoor breeding environment. The caterpillars were given young leaves of the Yellow Saraca to feed on.


A video clip showing the caterpillars of the Ciliate Blue in various instars living in the company of the weaver ants in the wild on a tree of the Yellow Saraca.

Weaver ants attending to a pre-pupa (right) and a pupa (left) of the Ciliate Blue on the underside of a leaf of Saraca indica.

In the wild, caterpillars of the Ciliate Blue can sometimes be observed to share the same feeding site with caterpillars of the Common Tit (Hypolycaena erylus teatus) which are also constantly attended by weaver ants.

Weaver ant attending to final instar caterpillars of the Ciliate Blue and the Common Tit on a young leaf of the Yellow Saraca.

The ovipositing female typically looks for parts of the host plant densely populated by the weaver ant, and lay its eggs there.  The eggs are laid in small to large clusters on the underside of a leaf or a twig, under the watchful eyes of the weaver ants which do not attack the female. At times, the eggs are even laid directly on the nest of the weaver ant.

A female Ciliate Blue laying eggs on the underside of a leaf of Saraca indica.

A cluster of eggs of the Ciliate Blue laid on the leaf underside of Saraca indica.

A weaver ant checking the cluster of eggs (shown above).

A time lapse sequence showing a Ciliate Blue female laying eggs on the underside of a twig of Saraca indica as weaver ants wandering by.

A weaver ant checking the cluster of eggs laid on a twig.

Each egg is about 0.5mm in basal diameter, and whitish with a strong greenish undertone. It is discoid-shaped with a slightly depressed micropylar at the center of the top surface. The egg surface is reticulated with a very dense pattern of tiny ridges and pointed protrusions.

Close-up views of eggs of the Ciliate Blue. Basal diameter: 0.5mm.

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 a pale yellowish body with a length of about 1mm. Its head is similarly coloured. The body also features pale yellowish  setae (hair) dorso-laterally and along the body fringe.  These young caterpillars feed by grazing on the surface of the young leaf of the host plant. The body colour could remain pale yellowish or  change to  a darker shade of yellow as growth progresses.  After about 2.5-3 days of growth in the first instar, and reaching a length of about 2mm, the caterpillar moults to the next instar. 

In the wild, it had been observed that early instar caterpillars of the Ciliate Blue were regularly picked up by the worker ants and carried back to the ant nests. It is thought that these young caterpillars feed and grow within the nests before being carried out when they reach later instars.

Hatching time! Both newly hatched caterpillars as well as those in the process of devouring egg shell.

Two views of a newly hatched caterpillar, length: 1mm.

Two views of a 1st instar caterpillar, length: 1.6mm.

A large number of early 1st instar caterpillars feasting on leaf lamina of the host plant.

Two views of a late 1st instar caterpillar, dormant prior to its moult, length: 1.95mm.

A group of late 1st instar caterpillars, dormant prior to its moult.

Both 1st and instar caterpillars being attended by weaver ants on a leaf of a Syzygium sp.

Both 1st and instar caterpillars being attended by weaver ants on a leaf of the Yellow Saraca.

In the 2nd instar, there are numerous tiny  speckles covering the body surface.  The caterpillar is pale to dark yellowish in colour. At this stage, the dorsal nectary organ on the 7th abdominal segment is present and rather prominent. The 2nd instar caterpillar reaches up to a length of about 4mm, and after about 2.5-3 days in this stage, it moults again.

Two views of a 2nd instar caterpillar, early in this stage, length: 2.5mm.

Two views of a 2nd instar caterpillar, length:2.8mm.

Two views of a late 2nd instar caterpillar, dormant prior to its moult, length:4.1mm.

Two weaver ants in a tussle over a 2nd instar caterpillar of the Ciliate Blue.

A weaver ant transporting a 2nd instar caterpillar of the Ciliate Blue.

A weaver ant attending to caterpillars of the Ciliate Blue.

The 3rd instar caterpillar has numerous speckles covering its body surface which is pale to dark yelowish green. Pale brownish to reddish dorso-lateral bands stretch from the prothorax to the 6th abdominal segment. Between these bands, 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, on the 7th and 8th abdominal segments respectively, are now readily observed. The 3rd instar takes about 3.5 to 4 days to complete with the body length reaching about 7.5mm.

A newly moulted 3rd instar caterpillar.

Two views of a 3rd instar caterpillar, early in this stage, length: 4.6mm.

Two views of a 3rd instar caterpillar, length: 7mm.

Two views of a 3rd instar caterpillar, dormant prior to its moult, length: 7.4mm.

A group of late 3rd instar caterpillars, dormant prior to the moult to the next instar.

Two weaver ants attending to a 3rd instar caterpillar of the Ciliate Blue on a leaf of the Yellow Saraca.

A weaver ant attending to a 3rd instar caterpillar of the Ciliate Blue on a leaf of a Syzygium sp.

In the 4th instar, the caterpillar has its body ground colour featured in varying degrees of yellowish green (yellow to green, and intermediaries). Inner and adjacent to the dorsal-lateral bands (which are reddish brown in most specimens), thin whitish bands are present. In the area enclosed by the dorsal-lateral bands, the dorsum could be either reddish brown or green, and decorated with chevron markings in most body segments. In some specimens, the chevron markings are indistinct or absent, and in other specimens, reddish brown to dark brown coloration spreads beyond the dorsal bands and spanning     almost entire body surface.The dorsal nectary organ and the tentacular organs are prominent in this final instar of the larval phase of the life cycle.

A newly moulted 4th instar caterpillar.

Two views of a 4th instar caterpillar, early in this stage, length: 7.5mm.

Two views of a 4th instar caterpillar, length: 10.5mm.

An animated sequence showing twelve 4th instar caterpillars of the Ciliate Blue, showing colour/marking variations.

Two weaver ants attending to an early 4th instar caterpillar of the Ciliate Blue.

Weaver ants attending to a 4th instar caterpillar of the Ciliate Blue.

Weaver ants attending to a 4th instar caterpillar of the Ciliate Blue.

Weaver ants attending to a 4th instar caterpillar of the Ciliate Blue.

Weaver ants attending to a 4th instar caterpillar, with a 2nd instar caterpillar present nearby.

After about 4-5 days of feeding in the 4th instar and reaching a length of up to about 15.5mm, the caterpillar stops food intake and seeks out a pupation site. During this time, its body gradually shrinks and turns almost uniformly green. Typically the caterpillar chooses a spot on the underside of a leaf or a stem for its pupation site. The pre-pupatory caterpillar prepares for pupation by spinning a silk girdle and a silk pad to which it attaches itself via anal claspers.

Two views of a pre-pupa of the Ciliate Blue.

A video clip showing the pupation event of a Ciliate Blue caterpillar.

After about half a day as a pre-pupa, pupation takes place. The pupa has a typical lycaenid shape. The colour of the pupa varies drastically, ranging from the more common green colour, to colours such as pink, brown and black. A large diamond-shaped marking is present at the posterior end of the mesothorax on the dorsum. Pupal length: 9.8-11.3mm.

Two views of a green-coloured pupa of the Ciliate Blue.

An animated sequence depicing six pupae of the Ciliate Blue, showing variations in colour.

Weaver ants checking a brown-coloured pupa of the Ciliate Blue.

Weaver ants checking a green-coloured pupa of the Ciliate Blue.

About five 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 Ciliate Blue.

A newly eclosed male  Ciliate Blue.

A video clip showing the eclosion event of a female Cilite Blue butterfly.

References:
  • The symbiosis between the weaver ant, Oecophylla smaragdina, and Anthene emolus, an obligate myrmecophilous lycaenid butterfly, K. Fiedler and U. Maschwitz, Journal of Natural History, vol. 23, pp.833-846, 1989.
  • Differences in worker caste behaviour of Oecophylla smaragdina in response to larvae of Anthene emolus, E. V. Saarinen, Biological Journal of the Linnean Society, vol. 88, no.3, pp. 391-395, 2006.
  • Symbiotic Relationship Between Anthene emolus and Oecophylla smaragdina: An obligate mutualism in the Malaysian rainforest, E. V. Heffernan, Doctoral dissertation, University of Florida, 2004.
  • [C&P4] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society, 1992.
  • A Field Guide to the Butterflies of Singapore, Khew S.K., Ink On Paper Communications, 2010.
Text by Horace Tan, Photos by Simon Sng, Ellen Tan, Nelson Ong  and Horace Tan.