Butterfly of the Month - January 2010

Butterfly of the Month - January 2010
The Common Birdwing (Troides helena cerberus)

We start a fresh decade in the 21st Century with one of the largest butterflies in Singapore, the Common Birdwing. This species is not rare, and where the host plant is plentiful, there have been occasions where a number of individuals have been seen, as were their caterpillars, in locations like the Singapore Botanic Gardens, Singapore Zoological Gardens and Alexandra Hospital Butterfly Trail.

It is always an uplifting experience to see a Birdwing in flight - with its contrasty black-and-yellow colour scheme, the butterfly is conspicuous, large and showy. As it flutters and glides high at the treetops, the flight of the Birdwing is reminiscent of that of birds. The species descends to flowering plants like the Pagoda Flower, Hibiscus, and even Lantana, to feed. Typical of the flight of Papilionidae, the Common Birdwing's forewings flutter rapidly, whilst the hindwings are kept almost still, when it is feeding at flowers.

The Common Birdwing has black forewings with the veins beyond the cell edged with pale greyish streaks that are more conspicuous in the female. Some individuals however, may lack these pale streaks altogether. The hindwing is a rich golden yellow edged with black, and the female has a complete series of large black submarginal spots that are usually not conjoined. Males may have one or more spots, but never a complete series

Unlike the typical males of the Papilionidae, the male Common Birdwing is rarely observed puddling at muddy footpaths and stream banks. Both sexes can often be found flying in the vicinity of their host plant, Aristolochia acuminata.

Whilst the species cannot be considered rare, it is a species that is vulnerable to extinction if its host plant disappears from Singapore's parks and forests. This species shares the host plant with another Papilionidae, the Common Rose (Pachliopta aristolochiae asteris).

The Common Birdwing has the distinction of being the only species in the Singapore Checklist to be listed in the Convention on International Trade in Endangered Species (or CITES) Appendix II. Appendix II lists species that are not necessarily now threatened with extinction but that may become so unless trade is closely controlled.

The conservation strategy to enhance the chances of survival of this spectacular species would be to continue to cultivate its host plant in more locations especially in parks, park connectors and even private homes in Singapore.

Text by Khew SK : Photos by Bobby Mun, Khew SK, Terry Ong, Benedict Tay & Anthony Wong

Life History of the Plain Palm Dart

Life History of the Plain Palm Dart (Cephrenes acalle niasicus)



Butterfly Biodata:
Genus: Cephrenes Waterhouse & Lyell, 1914.
Species: acalle Hopffer, 1874
Sub-species: niasicus Plotz, 1886
Wingspan of Adult Butterfly: 45mm
Caterpillar Host Plants: Livistona sp. (Arecaceae), Cocos nucifera (Arecaceae; common name: coconut)


A male Plain Palm Dart visiting flowers of Syzygium species in a hill park.


A female Plain Palm Dart visiting flowers of Syzygium species in a hill park.

Physical Description of Adult Butterfly:

The adults, especially the males, are similar to Telicota spp. but are generally larger. However, unlike the Telicota spp, the male lacks a stigma (a secondary sexual character). Above, the male is dark brown with orange-yellow markings, which includes on the forewing, a post-discal band running from dorsum to vein 6 and three subapical spots, and on the hindwing, an orange-yellow discal band, central streaks and tornal cilia. The female's markings are usually very sullied. and the hindwing beneath has an oily sheen and may be coloured green, bluish and purple. Beneath, the male is ochreous with markings outlined in black spots. The female has an oily sheen, especially on the forewing apex and hindwing, and may be coloured green, bluish and purplish. In the females, the markings on the hindwing are generally defined by dark spots, but these could be absent in some specimens, making the markings obscure.

A newly eclosed male Plain Palm Dart flexing its proboscis.


Another male Plain Palm Dart visiting flowers of Syzygium species in a hill park.

Field Observations of Butterfly Behaviour:
The adults are rarely encountered in Singapore, due likely to their habit of being more active at dawn and dusk. So far, sightings of the swift flying adults have been restricted to parts of Southern Ridges and in Pulau Ubin, and typically on flowering plants such as the Syzygium species.

Early Stages:


Host plant: Livistona sp.

The eggs are laid singly on the underside of a host plant leaf. Each dome-shaped egg is creamy yellow with a flat base. The micropylar sits atop. Upon close inspection, numerous tiny and inconspicuous pits can be seen on the egg surface. The eggs are rather large with a diameter of about 1.7-1.8mm.

Two views of an egg of the Plain Palm Dart, diameter: 1.75mm.

It takes 5-6 days for the collected egg to hatch. The egg first develops red patches on the pole and in an equatorial belt, and then turns dark pinkish-red with the dark head capsule becoming visible through the egg shell. The reddish coloration fades away in the day prior to the hatching event.

Maturing egg with a red polar patch and a red equatorial belt.


Mature egg with a faint view of the head, with the one in the right panel closer to hatching.

The young caterpillar eats just enough of the shell to emerge, and then immediately proceeds to finish the remaining egg shell. The newly hatched has a length of 5-5.5mm. Its creamy white body is cylindrical in shape with dorsal, lateral and sub-spiracular setae, all of which are short with the exception of those at the posterior end. The large head is black with a few short white setae. A black collar, as in common in many 1st instar skipper caterpillars, is found on the prothorax just behind the head. All instars of the the Plain Palm Dart feed on the mature leaves of the host plant, and constructs leaf shelters by joining folds of a leaf together.

Top: Newly hatched 1st instar caterpillar, length: 5.5mm.
Bottom: A few hours old with a greenish undertone (after some bites of the host plant leaves).

The body soon takes on a green undertone after a few feeding sessions on the leaf. Its movement on leaf was observed to be rather quick-paced. The 1st instar takes a total of 4-5 days to complete with body length reaching 7.5-11mm.

Two views of a 1st instar caterpillar, late in this stage, length: 7.5mm.
With leaf shelter almost closed (top); and opened up (bottom).

The body of the 2nd instar caterpillar resembles that of the first instar, but with the dark collar on the prothorax absent. The tuff of long setae at the posterior end is still prominent lyfeatured. This instar lasts a total of 3-5 days with the body length reaching up to 14mm.

Two views of a 2nd instar caterpillar, newly moulted, length: 7mm.


Two views of a 2nd instar caterpillar, late in this stage, length: 14mm.

The yellowish green 3nd instar caterpillar resembles the 2nd instar caterpillar except for variations in coloration and markings on the head capsule. While some specimens still sport a black head capsule, others have light brown to beige head capsule margined in dark brown with varying extent of light brown/beige as the base colour. This instar lasts a total of 4-6 days with the body length reaching up to 19-21mm.

3rd instar caterpillars, early in this stage.
Lengths: 13.5mm (top,female); 14mm (bottom, male).


3nd instar caterpillar, late in this stage, length: 20mm.

The 4th instar caterpillar is now consistent in having a light brown to beige head capsule margined in dark to reddish brown. This instar lasts 6-7 days with the body length reaching up to 27-31mm.

4th instar caterpillar, early in this stage. Lengths: 17mm (top), 19mm (bottom).


Two views of a 4th instar caterpillar, late in this stage, length: 29mm.

A dark green dorsal line, faint in the late 4th instar caterpillar, becomes prominent in the 5th instar.


Two views of a female 5th instar caterpillar, early in this stage. Length: 32mm.


Two views of a male 5th instar caterpillar, early in this stage. Length: 32mm.

The 5th instar takes about 7-8 days to complete with the body length reaching up to 43mm, In the last day of this instar, the caterpillar ceases feeding and its body colour turns milky green with a strong pinky undertone.

Two views of 5th instar caterpillar, late in this stage. Top: male (42mm), female (43mm).


Two views of a 5th instar caterpillar, with body color changes prior to becoming a pre-pupa.

Towards the end of 5th instar, the body of the caterpillar shortens appreciably. Soon the caterpillar becomes dormant in a leaf shelter which it seals with a copious amount of silk threads. In the tightly closed pupation shelter, the caterpillar also secretes large quantity of whitish waxy substance. This prepupatory phase lasts for 1-2 days.

Two views of a pre-pupa of The Plain Palm Dart.

Pupation takes place within the leaf shelter. The pupa does not have a cremaster nor a silk girdle and it is mainly secured with tightly woven silk threads in the shelter. It has a short thorax, a rather long abdomen, a short and pointed rostrum. The body is pale green in the thorax and wing pad areas, but pale yellowish brown in the abdomen. Length of pupae: 21-26mm.

Two views of a pupa of the Plain Palm Dart, length:24mm

After 8-9days, the pupa becomes mostly brown with the wing pad areas showing the orangy markings on the forewing upperside. Eclosion takes place the next day.

Three views of a mature pupa of the Plain Palm Dart.


A newly eclosed female Plain Palm Dart.


A newly eclosed male Plain Palm Dart.

References:

• 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 Khew SK and Horace Tan

Butterfly Survival Strategies - Part 2

Butterfly Survival Strategies - Part 2
Cryptic colouration, masquerade, startle, dazzle and decoy

A Dark Blue Jungle Glory perches on a leaf. Its cryptic undersides will render the butterfly well camouflaged when it forages amongst dead leaf litter on the forest floor.

In the first part of this series, we saw how some butterfly species have evolved to mimic their unpalatable cousins for protection against predators. This phenomenon of protective colouration gives the mimic a better chance of survival in the field, and in particular, females of the species, a higher odds of survival long enough to lay her eggs for the next generation.

A typical forest floor covered with dead leaf litter and twigs. Can you spot the two butterflies feeding on rotting matter on the forest floor?

In this part, we look firstly at adaptive colouration of butterflies based on the need of concealment or crypsis (defined simply as a strategy to reduce the probability of detection). This principle of concealment throught colouration was discussed by AR Wallace as the "visual similarity between animal and its background". This theory has been explained by many examples in the animal world - from the white polar bears that live in essentially white snow-covered habitats, to the colour differences in marine animals like sharks where its dorsal and ventral colour differences help in concealment of its presence in its environment, depending on whether viewed from above or below.

Camouflage

Saturns feeding on rotting fruit. How many can you see in the picture?

There are many examples in butterfly evolution, where cryptic colouration has been employed to render the butterfly 'invisible' to predators. This is done via disruptive patterning and colours to resemble its surroundings. The objective here of course, is the theory supporting the notion that predators 'cannot attack what the cannot see'.

Another Dark Blue Jungle Glory well camouflaged amongst dead leaf litter on the forest floor

Cryptic colouration, coupled with the behaviour of the various butterfly species in their preferred habitats is one of their survival strategies to avoid being predated upon for as long as possible.

Five large Morphinae with cryptic colouration on the undersides of the wings. With eyespots, lines that break the silhouette and colours that blend in with the forest floor habitats that they frequent, their camouflage help them stay 'invisible' from predators as they feed. Clockwise from top left - Koh-I-Noor (Amathuxidia amathaon), Tufted Jungle King (Thauria aliris), Giant Saturn (Zeuxidia aurelius), Dark Jungle Glory (Thaumantis noureddin) and Palm King (Amathusia phidippus)

Flash and Dazzle

In what is described as "startling patterns", prominent eyespots in butterflies have been shown to divert the attention of inexperienced avian predators. In his experiments with the Peacock Butterfly (Inachis io), David Blest (1957) found that this 'startle display' made young birds back off, even if for a moment, giving the butterfly that fleeting moment to escape. Locally, related species like the Junonia probably have the same effect on predators.

Large eyespots on the wings of the butterflies that may startle would-be attackers into hesitating for a fleeting moment will allow the butterfly to escape with its life

Another example of this strategy is the Great Helen (Papilio iswara iswara). At rest with its wings opened flat, the butterfly's forewings conceal the white patch on the hindwings, making it appear totally black. But when started, it flashes the white patch to 'dazzle' a would-be predator momentarily, giving it a precious moment to make good its escape.

The Great Helen is a good example of a species that employs "dazzle" to startle its would-be attacker. When at rest, the large white patches of the wings are hidden. When alarmed, it takes off, flashing the white patches that may catch the attacker off-guard whilst it is startled for a moment

Many species of butterflies also display an array of eyespots - some on the uppersides and some on the undersides of the wings. Eyes or the display of eyes, tend to make a predator wonder if there are indeed any other animal lying in wait for it. A momentary hesitance makes a difference in whether the butterfly escapes or ends up as lunch.

Eyespots on the outer fringe of the wings of some Satyrinae may cause some inexperienced predators to hesitate as they check out the eyes.

In some species like the Mycalesis, the spots are always ranged along the outer margins of the wings, never close to the body. Even if a predator decides to attack the 'eyes', it will take out a part of the butterfly's wing that may not be critical, allowing the butterfly to escape with its life, albeit without a small piece of its wings.

Masquerade

The Leaf Butterfly is a pretty iridescent blue above with orange bands, but when alarmed it settles with its wings closed to resemble a dead leaf.

As an alternative to purely employing cryptic patterns to camouflage itself, some butterfly species employ the strategy of masquerading as a non-palatable part of its environment, or at least 'pretend' to be something else to conceal itself. The famous Leaf Butterfly (Kallima limborgii) in Malaysia and (Kallima inachus) in Thailand and northwards, and (Kallima paralekta) in Java and southwards, demonstrates this method of concealment.

Another shot of the Leaf Butterfly masquerading as a dead leaf whilst it feeds

On the upperside, the butterfly is a rich purple blue, with a broad orange subapical band on the forewing. The underside very closely resembles a dead leaf, complete with a midrib, petiole and even patches of fungal growth on the leaf!

The undersides of the Autumn Leaf and Saturn also resemble dead leaves. Note the colourful orange upperside of the Autumn Leaf when it spreads its wings to sunbathe.

In Singapore, several other species like the Autumn Leaf (Doleschallia bisaltide) and to a certain extent, the Saturn (Zeuxidia amethystus) are less successful examples of trying to masquerade as dead leaves.

Decoy

Many Lycaenids display "false heads" complete with eyes and antennae to fool predators into attacking the "wrong" side of the butterfly

Many Lycaenidae are excellent examples of employing the strategy of creating 'decoys' whereby a predator is fooled into attacking the less vital parts of the butterfly. These species have evolved to create a 'false head' whereby the tornal area of the hindwing featuring a prominent 'eye' with one or more pairs of tails making them appear like antennae. Indeed, in the field, many of these species also accentuate this part their hindwings by moving them up and down when at rest, causing the 'false head' to be more active and calling attention to the 'wrong side' of the butterfly to a would-be predator.

Underside of the Common Red Flash featuring false eyes and antennae. Below is a shot depicting a possible survivor of an avian attack with the hindwings showing bite marks in a previous encounter.

The filamentous white-tipped tails of many species are also very 'lively' when wafted in a breeze, as are the long and white tails of many of the long-tailed Lycaenids. Coupled with the patterns, colours and tails, these butterfly species create a 'decoy' false head so that a predator attacks a less vital part of the butterfly, giving it a chance to survive and escape, but without a piece of its hindwings.

An Ambon Onyx showing off its "false head"

So now we see, despite being virtually harmless and unable to defend themselves with any aggressive 'weaponry', natural selection has allowed butterflies to adapt and evolve other strategies to even the odds of survival in the field via the colours and shapes of their wings, and their behaviour in their preferred habitats.

Text by Khew SK : Photos by Goh LC, Khew SK, Tan CP & Yong San