Butterfly of the Month - August 2013

Butterfly of the Month - August 2013
The Mangrove Tree Nymph (Idea leuconoe chersonesia)


A magnificent individual of the Mangrove Tree Nymph spotted on Pulau Ubin last month

The aftermath of the haze that affected Singapore and southern Johor in the month of June appears to have created some delayed effect on the butterfly population. Although the haze has abated, perhaps due to the combination of the rains and also the Indonesian government's timely action to curtail the open burning of forests in Sumatra, the particles in the air during the height of the haze may have been fatal to the caterpillars of various stages.

Interestingly, if we tracked the average time lag between the early caterpillar instars, pupation and eclosion of the majority of butterfly species, it appears to correlate with the time that these butterflies would have eclosed in early August. All over Singapore, there is an apparent reduction in the numbers of butterflies in many areas where they are usually found. Is this a coincidence? Or really a result of the environmental damage caused to butterflies by the recent haze? Perhaps this is a study that academic researchers may want to pursue to ascertain the extent of the damage caused by the haze.

August saw the celebration of Singapore's 48th birthday on 9th, as the Muslim community also celebrated Hari Raya Puasa a day earlier. The long 4-day weekend is a much welcomed break for many, although ButterflyCircle members' outings in Singapore seemed to re-affirm the low butterfly activity across the island. It is hoped that our winged jewels will spring back again in numbers, as they have been doing so in past years.

We feature the very rare Mangrove Tree Nymph (Idea leuconoe chersonesia) as our Butterfly of the Month for August. This species was first re-discovered on the military training island of Pulau Tekong in the early 2000's during an NParks survey of the island. Subsequent trips indicate that there was a small but highly threatened population of this large Idea species in the mangrove areas on the north of the island. Since then, there were some unconfirmed sightings of the species in the neighbouring island of Pulau Ubin.

The Mangrove Tree Nymph feeding on the flowers of the Peacock Flower bush

Late last month, during a ButterflyCircle outing to Pulau Ubin, members spotted a large black-and-white butterfly flying slowly and feeding on the Peacock Flower (Caesalpinia pulcherrima). It was confirmed to be the Mangrove Tree Nymph! The large individual, which appeared to be a female, was flying up and down, teasing our members who were trying hard to get a good shot of it. After feeding at a few flowers, it decided to take refuge in the shaded forested area nearby, and rested a few times. We continued following it until it decided to move off elsewhere and flew high above the treetops and out of sight.

The Mangrove Tree Nymph soaring high in the air

It was indeed exciting to see the Mangrove Tree Nymph after so many years, and we hope that it is successfully breeding in the mangrove areas of Pulau Ubin. The caterpillar host plant is probably one of the lactiferous plants of the Apocynaceae family. It would be great if the life history could be recorded before this species disappears from its preferred mangrove habitats that is progressively disappearing from Singapore and Malaysia.

The Mangrove Tree Nymph is a large butterfly, with a wingspan usually exceeding 130mm and often reaching 150mm or more. It displays the aposematic black and white colours like the other species of its genus. It features large black spots on both wings where the marginal and submarginal black spots are conjoined to form an irregular black band. The post-discal triangular spots on the hindwings are large and always touching the black veins, forming a jagged black band. The wing bases are yellow tinted.

The Mangrove Tree Nymph is a very rare species that occurs in coastal mangrove habitats. It is known to occur in Pulau Tioman in Malaysia and believed to also occur in the mangrove areas of Johor. A recent survey on one of the small offshore islands near the Indonesian resort island of Batam also yielded a sighting of the Mangrove Tree Nymph in the mangrove area of the island.

The Taiwan Tree Nymph (Idea leuconoe clara) shot at Sentosa Butterfly Park

The species is not to be confused with the abundant and easily bred subspecies clara that originates from Taiwan. Another possible subspecies would be siamensis that occurs in Thailand.  This subspecies (either clara or siamensis) occurs in many butterfly parks and farms across the globe and is bred for its showy appearance - popular with visitors to these butterfly enclosures.

Thus far, it has been seen regularly in butterfly parks in Penang, Kuala Lumpur, Malacca and as far north as the Phuket Butterfly Farm in Thailand. In Singapore, it is a regular "resident" species found at the Fragile Forest enclosure at the Singapore Zoo, the Sentosa Butterfly Park, Changi Airport Terminal 3 Butterfly Garden and the Hort Park Butterfly Garden.

A mating pair of the Tree Nymph shot at Phuket Butterfly Park.  Possibly subspecies siamensis?

The subspecies clara as it is known at the moment, has a whiter appearance, with the black markings on the wings reduced as compared to subspecies chersonesia. Another related subspecies, siamensis which has a similar appearance to subspecies clara also occurs in Thailand. A characteristic feature is that the post-discal spots on the hindwings, particularly in spaces 4, 5 and 6 are much reduced and not conjoined.  

Given the relative abundance of this non-native species, there is a high possibility of escapees from the various butterfly parks. Indeed, two individuals were spotted in the Sime Forest of the Central Catchment area (and captured) in 2004 and 2005. It is interesting that no escapee has been able to colonise any area in Singapore as yet. Perhaps its preferred caterpillar host plant is not available in abundance, and unable to support any succeeding generations of these escapees.

In any case, we hope that the opportune sighting of the real McCoy, the Mangrove Tree Nymph ssp chersonesia at Pulau Ubin is a good sign that the species still exists in Singapore. Though its hold on to survival is tenuous and is considered a critically endangered species, we hope that it will continue to survive in the remaining mangrove habitats of Singapore for many years to come.

Text by Khew SK : Photos by Chng CK, Goh EC, Khew SK, Loke PF, Nona Ooi, Simon Sng, Anthony Wong & Mark Wong.

Special footnote : In the Butterflies of the Malay Peninsula, it was suggested that the various subspecies of Idea leuconoe could in reality be two distinct species, due to differences in their caterpillars. In which case, the Mangrove Tree Nymph would be assigned the name Idea engania (Doherty, 1891). Until there is a definitive research and a published paper on this, the Mangrove Tree Nymph remains subspecies chersonesia of Idea leuconoe for the time being.

Flight of Fancy @ GB

Flight of Fancy Photography Exhibition
ButterflyCircle @ Gardens by the Bay

A photography exhibition showcasing the biodiversity at Gardens by the Bay was launched on 1 Aug 2013. This exhibition features the work of many individuals who have captured the beauty of birds, butterflies and dragonflies at Gardens by the Bay. Despite being an urban park with man-made structures, Gardens by the Bay is still rich in biodiversity, and this exhibition captures the variety of beautiful flying creatures that have made the Gardens home.

ButterflyCircle members Sunny Chir, Chng CK, Huang CJ, Khew SK, Loke PF, Nelson Ong, Ellen Tan, Anthony Wong & Mark Wong contributed their photographs to make up part of the exhibition of 50 panels. A commemorative $2 stamp was also issued to feature the biodiversity of Gardens by the Bay.

ButterflyCircle member Chng CK stands proudly beside his masterpiece!

The Flight of Fancy Exhibition is held at the Lion Grove of Gardens by the Bay along the sheltered corridor where some of the more popular F&B outlets are located. Do visit the exhibition to see the awesome biodiversity of GB and also ButterflyCircle members' works!  All images were shot on-site at Gardens by the Bay.  

© Poster by Gardens by the Bay

ButterflyCircle would also like to take this opportunity to wish all Singaporeans a Happy 48th Birthday! Majulah Singapura!!!

Butterflies Galore! : Leopard

Butterflies Galore! 
The Leopard (Phalanta phalantha phalantha)

This active and always on the move bright orange butterfly is common and is found mainly in urban parks and gardens where its caterpillar host plants - Salix babylonica (Weeping Willow) and Flacourtia inermis (Rukam assam) grows. The butterfly is fast flying and often feeds and moves quickly with half-opened wings. It is believed to be a relative of the temperate-climate Fritillary butterflies.

This Leopard was photographed by ButterflyCircle member Sunny Chir. It is shown here displaying the underside of its wings, which appears with a purplish wash when seen in sidelight. It is feeding on the ruby-red flower of the Leea rubra.

Butterflies Galore! : White Palm Bob

Butterflies Galore! 
The White Palm Bob (Suastus everyx everyx)

This small and insignificant-looking skipper was a new discovery for Singapore when it was first encountered. Perhaps the early authors missed it as its distribution is rather local and restricted to habitats where its caterpillar host plant, a palm, grows. With a wingspan of up to only 28mm, it is a skittish flyer like most skippers, but prefers to lurk in the shady areas of the forests. It typically perches on the top surface of a leaf with its wings folded upright.

This White Palm Bob was photographed in the nature reserves by ButterflyCircle member Mark Wong. The butterfly is dark brown above, whilst the underside of the hindwing is largely whitened with a dark greyish spot at the dorsal area of the hindwing.

Life History of the Royal Assyrian

Life History of the Royal Assyrian (Terinos terpander robertsia)

Butterfly Biodata:
Genus: Terinos Boisduval, 1836
Species: terpander Hewitson, 1862
Subspecies: robertsia Butler, 1867
Wingspan of Adult Butterfly: 60-70mm
Caterpillar Local Host Plant : Rinorea anguifera (Violaceae).

Physical Description of Adult Butterfly:

The wings are angled with the hindwing slightly toothed at the end of vein 4. Above, the wings are rich purplish blue with two white spots in spaces 3 and 4 on the hindwing. Underneath, the wings are purple-brown with reddish brown and pale blue (shiny in fresh specimens) fasciae crossing both wings. The hindwing has a white submarginal band which is broader and more lunulate in spaces 2 to 4, and a series of dark purple brown post-discal spots which are ringed in orange.

Field Observations of Butterfly Behaviour:

The Royal Assyrian is moderately rare in Singapore. The species is usually encountered in parts of the nature reserves where its host plant, Rinorea anguifera, is growing. The adults have been observed to visit flowers for nectar. When resting, the adults typically perch on the underside of a leaf with its wings closed. The males have also been observed to puddle on damp patches.

Early Stages:

The sole local host plant recorded, Rinorea anguifera, is found at several sites within the Central Catchment Reserves. The caterpillars of the Royal Assyrian feed on young and immature leaves of the host plant.

Local host plant: Rinorea anguifera.

The fruits of Rinorea anguifera.

The eggs of the Royal Assyrian are laid singly on a leaf of the host plant, typically on its under surface. Each creamy white egg is somewhat globular with its surface covered with rectangular pits sandwitched between longitudinal ridges. It has a cross-sectional diameter of about 0.7-0.8mm.

An egg of the Royal Assyrian laid on the underside of a leaf.

Two views of an egg of the Royal Assyrian.

Each egg takes about 3 days to hatch. The young caterpillar nibbles away a portion of the egg shell to emerge. It then proceeds to nibble away the rest of the egg shell for its first meal.

Two views of a maturing egg of the Royal Assyrian. The head and body setae can be vaguely seen through the egg shell.

The newly hatched is creamy white with a a body length of about 2mm, and a head capsule which is pale beige brown. The body surface has dorso-lateral and lateral rows of short dark setae.

Two views of a newly hatched caterpillar, length: 2mm.

Two views of a 1st instar caterpillar, length: 3.6mm.

As the 1st instar caterpillar grows up to a length of about 4 to 4.5mm, the body turns yellowish with a strong green undertone. After about 2 days in the 1st instar, the caterpillar moults to the next instar.

A late 1st instar caterpillar, dormant prior to its moult, length: 4.2mm.

The 2nd instar caterpillar has a yellowish body with a green undertone. The head capsule is pale yellow with two tiny black cephalic horns. The numerous fine setae in the 1st instar are replaced by dorso-lateral and lateral rows of moderately long and pointed black spines. This instar lasts about 2 days with the body length reaching up to 6.5mm before the next moult.

A newly moulted 2nd instar caterpillar, length: 3mm.

Two views of a 2nd instar caterpillar, length: 5.8mm.

Two views of a late 2nd instar caterpillar, dormant prior to its moult, length: 6mm.

The 3rd instar caterpillar resembles the 2nd instar caterpillar closely. The main change occurs in the head capsule where the two cephalic horns are more pointed and longer. A black patch can be seen at the foot of each horn. Further black patches can be found on both sides of the adfrontal area, and where the stemmata (eyes) are. All the pointed spines are proportionately longer. The 3rd instar takes about 2-3 days to complete with the body length reaching up to 10-11mm.

Two views of a 3rd instar caterpillar, early in this stage, length: 6.3mm.

Two views of a 3rd instar caterpillar, length: 11mm.

Two views of a late 3rd instar caterpillar, dormant prior to its moult, length: 10mm.

In the 4th instar, the caterpillar again has proportionally longer cephalic horns and body spines. There are discontinuous dark brown dorsal patches adorning the yellowish green body. Faint white to pale yellowish bands, occuring dorso-laterally and laterally, become increasingly discernible as growth progresses in this instar. This penultimate instar lasts about 3-5 days with body length reaching about 22-24mm.

Two views of a 4th instar caterpillar, early in this stage, length: 12mm.

Two views of a 4th instar caterpillar, length: 17mm.

Two views of a late L4 caterpillar, dormant prior to its moult, length: 23mm.

The next moult brings the caterpillar to its 5th and final instar. Again the body spines are proportionately longer. Now the white and pale yellowish bands, occuring dorso-laterally and laterally, are broad and prominent. Also prominent at this stage is a bold whitish band passing through the spiracles on both sides of the body.

The head of a 4th instar caterpillar (left) and a 5th instar caterpillar (right).

Two views of an early 5th instar caterpillar, length: 21mm.

Two views of a 5th instar caterpillar, length: 34mm.

Two views of a 5th instar caterpillar, late in this stage, length: 40mm.

The 5th instar lasts for about 6-7 days, and the body length reaches up to 40mm. Towards the end of the 5th instar, the body gradually shortens in length with the body base colour turning to pale yellowish green. Eventually the caterpillar comes to rest on the underside of a leaf, typically on the midrib. Here it stays dormant for a while before spinning a silk pad and anchoring its anal claspers to it. It then becomes an pre-pupatory larva in this upside-down pose.

A pre-pupatory larva of the Royal Assyrian.

A Royal Assyrian caterpillar moults to its pupal stage.

Pupation takes place about 0.5-1 day later. The pupa suspends itself with a cremastral attachment to the silk pad on the substrate. The pupa is mainly green with yellow dorso-lateral processes on most body segments which are mostly short, pointed and red-tipped. The exceptions are in the 2nd thoracic segment, 3rd, 5th and 7th abdominal segments where they are much longer (the longest occurring on the 3rd abdominal segment) and angled laterally. Each pupa has a pair of short red-tipped cephalic horns. A silverish dorsal patch is found on the 2nd abdominal segment. Length of pupae: 18-19mm.

Two views of a pupa of the Royal Assyrian.

Two views of a Royal Assyrian caterpillar found in the field.

After 5 days of development, the pupa turns black as the development within the pupal case comes to an end. Purplish blue patches on the forewing are now visible on the wing pad through the pupal skin. The next day the adult butterfly emerges from the pupal case.

Two views of a maturing pupa of the Royal Assyrian.

A newly eclosed Royal Assyrian clinging on to its pupal case.

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, 2nd Edition, 2012
• A Field Guide to the Butterflies of Singapore, Khew S.K., Ink On Paper Communications, 2010.

Text by Horace Tan, Photos by L C Goh, Huang Caijin, Chng CK, Nelson Ong, Ben Jin Tan, Federick Ho, Sunny Chir, Khew SK and Horace Tan

Butterflies Galore! : Aberrant Oakblue

Butterflies Galore! 
The Aberrant Oakblue (Arhopala abseus abseus)

The diminutive Oakblue is one of many species in the genus Arhopala.  The many lookalike species in the genus is a nightmare to identify and distinguish the different species.  The Aberrant Oakblue is more distinctive in its markings, and is much easier to separate from the other species in the genus.  It is a fast flyer and is usually skittish.  It lurks in the shady forested understory in Singapore's nature reserves, but is quite widespread and is often observed in urban parks and gardens as well.

This Aberrant Oakblue was photographed by ButterflyCircle member Koh Cher Hern. It was perched on a leaf in its usual pose, with its wings folded upright. The hindwing features three pairs of threadlike white-tipped tails of which the longest pair is at vein 2b of the hindwing. The brilliant purple blue upperside can sometimes be seen as the butterfly takes off when disturbed.