Butterfly of the Month - August 2024

Butterfly of the Month - August 2024

The Singapore Four Line Blue (Nacaduba pavana singapura)

A couple more hours, and August 2024 will come to an end. August is the month when Singapore celebrates its National Day. Every year since this 'little red dot's' independence from Malaysia in 1965, Singaporeans of all walks of life come together to watch the parade at various designated locations in Singapore. It is a day of celebrations and pride as Singaporeans and residents wish the nation a happy birthday.

This year, 2024, Singapore celebrated its 59th year of independence. It was also a special year that marked the appointment of Singapore's fourth prime minister - Mr Lawrence Wong, who took over from former PM Lee Hsien Loong, who was prime minister from 2004 - 2024. It was also the first year that PM Lawrence Wong shared his vision for Singapore in his inaugural National Day Rally.

A Singapore Four Line Blue feeding on the flower of the Red Bush (Leea rubra)

It is therefore apt that, as a nation celebrates its 59th birthday, that we feature a small butterfly that carries the word 'singapura' in its taxonomic name - the Singapore Four Line Blue (Nacaduba pavana singapura). This small Lycaenidae that carries the subspecies name referring to Singapore, is one of the members of the 4-line blues of the genus Nacaduba.

The Singapore Four Line Blue has been described as "with a pale greyish blue male, and is seldom seen except in Singapore, where it is sometimes quite common on the landward edge of mangrove swamps."Indeed this is the case, where the species is a regular at the Sg Buloh Wetland Reserve (SBWR), Kranji Nature Trail and Mandai Mangroves where its caterpillar host plants Derris trifoliata (Leguminosae), Andira inermis (Leguminosae), Allophylus cobbe (Sapindaceae) grow quite commonly.

A female Singapore Four Line Blue with partially opened wings showing the uppersides of the wings

The butterfly is rather small, with a wingspan of usually less than 20mm. Above, the male is greyish blue with a thread-thin border; the female is brown with a pale blue discal patch on the forewing and blue dusting on the basal part of the hindwing. The species belongs to the pavana group of the genus - a primary characteristic being the lack of a pair of sub-basal lines on the underside of the forewing.

Underneath, both sexes are greyish brown with the bands composed of a double series of whitish striae inwardly lined with darker lines with the space between them appear to be paler than the ground colour. On each hindwing, there is an orange-crowned tornal spot lightly speckled with bluish-green metalic scaling. Next to the tornal spot, a pair of filamentous white-tipped tails occurs at end of vein 2. Marginal and submarginal spots are black and stand out against the ground colour of greyish brown.

The Singapore Four Line Blue is skittish and flies erratically as it searches for food or, in the case of the female, is looking for its caterpillar host plants to oviposit. It is alert and is difficult to photograph in the field due to its small size and erratic flight. However, when it is busy ovipositing or occasionally stopping to feed at flowering plants, it gives a fair chance for a determined butterfly photographer to get a good shot of it.

A female Singapore Four Line Blue ovipositing.

A Singapore Four Line Blue feeding on the flower of the Pig's Grass (Synedrella nodiflora)

Males of the Singapore Four Line Blue are seldom seen to puddle, like several of its other cousins in the genus Nacaduba. They are more often spotted feeding at flowers like the females. The complete life history of the Singapore Four Line Blue has been successfully recorded in Singapore, and is recorded here on this blog. The caterpillars are polyphagous and feed on at least three different host plants usually found growing in back-mangrove habitats.

Text by Khew SK : Photos by Federick Ho, Khew SK, Low JK, Ong LM, Horace Tan and Angela Yeo.

Life History of the Singapore Four-Line Blue

Life History of the Singapore Four-Line Blue (Nacaduba pavana singapura)

Butterfly Biodata:
Genus: Nacaduba Moore, 1881
Species: pavana Horsfield, 1828
Subspecies: singapura Corbet, 1938
Wingspan of Adult Butterfly: 26-30mm
Caterpillar Local Host Plants: Derris trifoliata (Leguminosae), Andira inermis (Leguminosae), Allophylus cobbe (Sapindaceae)





Physical Description of Adult Butterfly:

As a member of the pavana group (the Four-Line Blues), the adult does not have a basal pair of lines in the underside forewing cell. Above, the male is greyish  blue with a thread-thin  border; the female is brown with a pale blue discal patch on the forewing and blue dusting on the basal part of the hindwing.  Underneath, both sexes are greyish brown with the bands (post-discal, discal and basal) composed of a double series of whitish striae inwardly lined with darker lines with the space between them appear to be paler than the ground colour.  On each hindwing, there is an orange-crowned tornal spot lightly speckled with bluish-green metalic scaling.  Next to the tornal spot, a pair of filamentous white-tipped tails occurs at end of vein 2. Marginal and submarginal spots are black and stand out against the ground color of greyish brown.

Field Observations of Butterfly Behaviour:

Early researchers for butterflies in the Malay Peninsula from the 60s and 70s [C&P4] noted that Nacaduba pavana "is seldom seen except in Singapore, where it is sometimes quite common on the landward edge of mangrove swamps."  This observation still holds true today as recent sightings of this species have been confined to the northern and  north-western corner of the Singapore island in an area covering Sungei Buloh Wetland Reserve, Kranji Nature Trail and the Mandai Mangrove. The adults have been seen flying in the vicinity of their host plants, which are common in these habitats, visiting flowering plants, puddling on wet ground and performing oviposition rituals.

A female laying an egg on a young leaf of Derris trifoliata.


Another female ovipositing on a young leaf of Allophylus cobbe.

Early Stages:

The Singapore Four-Line Blue is polyphagous and so far three plant species found in the back mangrove habitats have been recorded as its host plants. The caterpillars feed on young and tender leaves and sometimes young shoots of these plants. As in the case for most lycaenidae species, the caterpillars of the Singapore Four-Line Blue  are typically tended by a number of ant species.

Local host plant #1: Andira inermis.
 

Local host plant #2: Allophylus cobbe.
 

A mother ovipositing on a cluster of flower buds of Derris trifoliata.


Another mother ovipositing on the young shoot of Andira inermis.

Eggs are laid on the young shoots or inflorescence of the host plants. It is not uncommon for a number of eggs to be found in close proximity on the same shoot, however the eggs occur singly rather than in clusters. Each egg is pale yellowish green, discoid and has a depressed micropylar on top. The egg surface is finely reticulated, slightly raised at the intersections of criss-crossing ridges. Th egg has a diameter of about 0.4-0.45mm.

Eggs on young shoot of Andira inermis with a 1st instar caterpillar nearby.


Two views of an egg of the Singapore Four-Line Blue. Diameter: 0.4mm.

It takes about  2 days for the egg to hatch. The young caterpillar consumes part of the egg shell to emerge. With a length of about 0.7-0.8mm, it has a pale yellowish body with long setae (hairs) dorsally and sub-spiracularly. The caterpillar assumes the typical woodlouse body shape as it grows. The body color  changes gradually to a brighter shade of yellow or red depending on the color form the caterpillar assumes. The first instar lasts for 1.5-2 days and the body length reaches about 1.8mm before the moult to the 2nd instar. A faint reddish brown patch appears on the dorsum of the 7th-9th abdominal segment towards the end of the first instar.

Two views of a newly hatched caterpillar, length: 0.8mm.


Two views of a 1st instar caterpillar, late in this stage, length: 1.8mm.


A red-form 1st instar caterpillar, late in this stage.

The long dorsal setae are absent in the 2nd instar caterpillar but now there are numerous short setae present all over the body surface. The body color is mainly yellow  with a greenish undertone or mainly red. A large, diffused, bright red to reddish brown patch occurs on the dorsum stretching from the 7th to the 9th abdominal segments in both color forms. The 2nd instar lasts for 1.5-2 days and the caterpillar grows to a length of about 3.5mm to 4mm.

Two views of a 2nd instar caterpillar, freshly moulted to this instar, length: 4mm.


A red-form 2nd instar caterpillar.


A field shot of caterpillars of Singapore Four-Line Blue on a young shoot with ants in attendance,
How many caterpillars can you see?

The 3rd instar caterpillar resembles the 2nd instar caterpillar closely but with the dorsal patch on the 7th to 9th abdominal segments much more prominent. In some specimens,  faint intermittent markings in red to reddish brown also appear dorso-laterally, and on the dorsum of the 2nd thoracic segment.  After 2 days in this stage with the body length reaching a maximum about 6.5mm, the next moult  brings the caterpillar to its final instar.

Two views of a 3rd instar caterpillar, early in this stage.


Two views of another 3rd instar caterpillar, length: 6mm.

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


A 3rd instar caterpillar with an attending ant in the field.

The 4th instar caterpillar are similar to the 3rd instar caterpillar but with all red and reddish brown markings much more prominently marked and in sharp contrast to the ground color.  The prothorcic shield is whitish and the dorsal nectary organ and ventacular organs are distinguishable on the posterior segments.

Two views of a red-form 4th instar caterpillar, length: 8.5mm.


Two views of a yellow-form 4th instar caterpillar, length: 12mm.

The 4th instar lasts for 2-3 days and the body grows up to a length of about 12mm. On the last day of this stage, the caterpillar ceases food intake and its body shrinks in length and decolorises to a dull shade of pale brown. The fully grown caterpillar finally comes to  rest on a spot among leaves where it readies the site for pupation by spinning a silk pad and a silk girdle to secure itself.

Two vies of a 4th instar caterpillar, late in this stage, with color change taken place, length: 11mm.


Two views of a girdled-down pre-pupa of the Singapore Four-Line Blue

The next day, after 6-7 days of larval growth, pupation finally takes place. The pupa has the typical lycaenid form, and is 8-8.5mm in length. It is mostly yellowish brown and speckled with black spots of various sizes and shapes.


Two views of a pupa of the Singapore Four-Line Blue

Five to six days later, the pupa becomes darkened in color signaling the imminent emergence of the adult. The markings on the forewing upperside becomes increasing obvious through the pupal skin. The next day the adult butterfly emerges from the mature pupa.

Two views of a mature male pupa showing the extensive bluish coloration in the wing pad.


Two views of a mature female pupa showing the much less extensive bluish coloration in the wing pad.

References:

• [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, 1st Edition, 2006

Text by Horace Tan, Photos by Federick Ho, Sunny Chir, Khew SK  and Horace Tan

Rhopalocera Singaporeana

Rhopalocera Singaporeana
A Tribute to 3 "Singapura" Butterflies

Singapore, an island at the southernmost tip of the Malay Peninsula, is a city-state comprising a total of 63 islands and islets with a combined land mass of 712.4 sq km. Singapore is highly urbanised city, but more than half the island is covered by greenery. Because of this, Singapore is often referred to as the "Garden City".

With a population of about 5.2 million people, it is considered a very densely populated country, in terms of persons per sq km. Despite being a land-scarce island city-state, about 23% of its land area is set aside for forests, parks & gardens and nature reserves. The National Parks Board, a statutory board that oversees the management of the Garden City, manages a total of 300 parks and 4 nature reserves and a total of 180 km of parks connectors which links the nature reserves, parks and urban gardens in a network of greenery covering the island.

A night shot of the Singapore City Skyline

It is always amazing to relate the story of how this "little red dot", as Singapore is fondly referred to, is home to a rich biodiversity of flora and fauna. Its butterfly biodiversity has crossed the 300 mark and is likely to increase as more species are discovered and re-discovered. This little piece of trivia is in itself remarkable, for example, when compared to Great Britain, where Singapore has more than five times the number of butterfly species compared to a country that is over 340 times the size of Singapore!

Hence, despite the highly urbanised built environment, Singapore's incredible and diverse range of flora and fauna stand testimony to the nature conservation efforts of governmental and non-governmental organisations.

The English name of Singapore is derived from the Malay word Singapura (Sanskrit: सिंहपुर, lit. Lion City), hence the customary reference to the nation as the Lion City. This week's article features butterflies in Singapore with their scientific names containing the word "singapura" in them.

The Blue Spotted Crow (Euploea midamus singapura)

The subspecies singapura of the Blue Spotted Crow is found in Singapore, as well as on the islands of Pulau Aur and Tioman in Malaysia. This subspecies lacks the blue sheen on the upperside forewings of the Malaysian subspecies chloe. It is a moderately common species that is often observed singly at both urban parks and gardens as well as in the nature reserves.

Males of the Blue Spotted Crow are often seen puddling at damp sandy spots near streams, and also observed at flowering trees in parks and gardens. When puddling it often returns repeatedly to the same spot even when disturbed, but can be skittish and not easily approached.

The butterfly is predominantly black with white spots typical of the Danainaes. It resembles the Spotted Black Crow very closely, with the difference in that there are four elongated white apical spots in the Blue Spotted Crow, compared to its lookalike's five spots.

The Singapore Fourline Blue (Nacaduba pavana singapura)

The Singapore Fourline Blue is the 2nd butterfly to carry the subspecies name singapura. The early authors commented that "it is seldom seen, except in Singapore, where it is sometimes quite common on the landward edge of mangrove swamps". This description is still accurate to this day, as the species continues to thrive at the Sungei Buloh Wetland Reserve, a protected mangrove nature reserve in Singapore.

The species' life history has been recorded on this blog here, with its host plants, Derris trifoliata (Leguminosae), Andira inermis (Leguminosae), Allophylus cobbe (Sapindaceae), all found at the landward edge of the mangrove swamps.

The Singapore Fourline Blue is a pale greyish blue with very thin borders on the upperside of the male, whilst the female is brown on the upperside with a blue wedge-shaped discal patch on the forewing and basal blue dusting on the hindwing.

The Shining Plushblue (Flos fulgida singhapura)

The last of the three butterfly species to bear Singapore in its name is the Shining Plushblue. The subspecies carries the name singhapura with the additional "h" in the name, but for all intents and purposes, it qualifies as a species that has the Singapore "brand".

It is a rather rare species that is most often encountered in Singapore's forested nature reserves, usually skulking amongst the shaded understorey along the forest edge and along paths. It is a fast flyer and is skittish. Usually, individuals are encountered, often in the company of species of the Arhopala genus.

The Shining Plushblue has a short stumpy tail at vein 2 of the hindwing and the dark brown bands across both wings on the underside. The males are dark blue above with almost indiscernible borders whilst females are a shining purple-blue with broad black borders. The partial life history of this species has also been recorded.

And so we celebrate three butterflies with their subspecies names carrying the name Singapore, or the Malay version "singapura" and "singhapura", giving these three butterflies a special pedigree that is closely associated with our beloved island in the sun!

Text by Khew SK : Photos by Sunny Chir, Chng CK, Henry Koh, Koh CH, Khew SK, Horace Tan, Mark Wong & Wong CM

References :

• Wikipedia article on Singapore : http://en.wikipedia.org/wiki/Singapore


• National Parks Board - Interesting Facts of our Garden City


• Your Official Gateway to Singapore website : http://app.www.sg/