THE BUTTERFLY: February 2009

Butterfly Predators - Death in the Wind

Butterfly Predators - Death in the Wind

A Robberfly, a vicious and efficient killing machine, impales a No Brand Grass Yellow and perches with its prize kill whilst sucking the nutritious juices out of the paralysed butterfly

It is quite well-known that butterflies are harmless insects that do not bite, sting, scratch or cause any harm to other animals. They are therefore vulnerable to the wide variety of predators in the animal world. Whilst many butterfly species have adapted themselves with survival strategies (which will be the subject of a future blog article here), they are still susceptible to ending up in the stomachs of various birds, animals and insects which prey on them.

A pair of Chestnut Headed BeeEaters with one Jamides sp. captured

Most observers will notice butterflies fluttering around flowers, frolicking in the sunshine, feeding, mating and going about their usual daily activities. However, dangers always lurk where the butterflies don't realise... until it's too late. Predators adopt a whole range of tactics to capture the unsuspecting butterflies - stealth, speed, surprise, traps and so on.

A dragonfly captures a Lycaenid

A butterfly's life is therefore fraught with dangers as they go about their daily routine. In this article, we feature a range of predatory attacks on butterflies by various predators. It is never a pretty sight to see any victim of a predator in the animal world, and even though the death of a butterfly comes with much less blood and gore, it is still nevertheless a pitiful sight, as the poor butterfly struggles for its last breath of life in the jaws of its nemesis.

A dragonfly with a Lycaenid prey in its jaws

The first category of predators use a combination of speed and stealth. These predators - birds, dragonflies, mantises, lizards, robberflies and wasps tend to wait till the unsuspecting prey comes close enough for the predator to launch a high speed attack on the butterfly. Very often, these attacks are not necessarily successful, and the butterfly escapes with a part of its wings torn off, or in some cases, the predator misses altogether when the butterfly makes a last-minute maneuver to get out of harm's way.

A mantis rips the head off a Tawny Coster whilst chewing up the body

The next group of predators combine stealth with poison - e.g. the Crab Spider. These masters of camouflage are often seen hiding amongst flowers and waiting for a hapless butterfly to fly close enough to be grabbed and bitten. The poison of these spiders appear to act swiftly, immobilising the prey within a few seconds, and paralysing the butterfly quickly as the spider sucks the life out of it.

A Crab Spider holds on tightly to an immobilised Nigger

Another Crab Spider, well camouflaged amongst the flowers of Pseuderanthemum sp, with a dead Centaur OakBlue in its jaws

Predators which use entrapment - usually web-weaving spiders of various species, often trap the unsuspecting butterflies that fly into the sticky web and get themselves entangled. From field observations, the butterflies that get themselves into this life-ending situation are those that are old and weathered. The stronger butterflies often have a chance of flapping violently and we have seen many that have escaped the jaws of the spider in good time, before the spider can sink its fangs into the butterfly.

A Golden Orb Spider makes a meal out of a trapped Great Eggfly

A spider drags a paralysed Palm Bob to its lair

In the natural world, the weak and old are often fair game for most predators. Once a butterfly is old, tattered and flying erratically due to injury or old age, they become easy prey to various predators which help end their lives swiftly and viciously.

A wasp rips apart a dead butterfly

Whilst an adult butterfly's life is always subject to dangers from predators as it goes about its daily activities, its early stages are also vulnerable to a variety of parasitism, particularly at the egg, caterpillar and pupa stages . Parasitic wasps and flies can often wipe out an entire clutch of eggs and experts often estimate that, in the wild, anything between only 1-5% of all the eggs that a single female lays in her lifetime produces the next generation of adult butterflies. The majority of the rest will perish due to predation and parasitism.

Even caterpillars are not spared. Here, the caterpillar of a Mottled Emigrant falls prey to Kerengga ants (Oecophylla smaragdina)

A Commander caterpillar with parasites on its body

A caterpillar surrounded by the pupae of parasites

Whenever we encounter a pretty butterfly fluttering amongst flowers and we admire its beauty and grace, we should always be reminded that these 'flying jewels' of the insect world are always in danger of ending up dead in the jaws of a predator in the next few moments.

Indeed, one can always argue that the biggest 'predator' may also be Man himself, as the destruction of habitats and the spraying of pesticides often kill far more butterflies in all stages of their life histories than any other predator can. As we take stock of our biodiversity in Singapore, and as more species are threatened by a variety of causes, there should be a strategy for the conservation of habitats and sanctuaries for our butterfly fauna to survive for our future generations to enjoy.

Text by Khew SK ; Photos by Con Foley, Chan SC, Horace Tan, Marcus Chua, Michael Lim, John Lee, Henry Koh, Jason Ng & Khew SK

Life History of the Plain Nawab

Life History of the Plain Nawab (Polyura hebe plautus)

Butterfly Biodata:
Genus: Polyura Billberg, 1820
Species: hebe Butler, 1866
Subspecies: plautus Fruhstorfer, 1898
Wingspan of Adult Butterfly: 65mm
Local Caterpillar Host Plants: Adenanthera pavonina (Red Saga), Falcataria moluccana (Albizia), Parkia speciosa (Petai), all belong to the family Leguminosae, sub-family Mimosoideae.
Physical Description of Adult Butterfly:
The forewing has a strongly arched costa, a pointed apex and a concave termen. The hindwing has a pair of short stubby tails. Above, the Plain Nawab is greenish white and the forewing has a broad black border decreasing markedly from the apex towards the tornus and base of the costa, and a moderately large greenish white spot in space 5. The hindwing has a series of marginal spots. The Singapore subspecies of P. hebe, represented by the race plautus, is different from its Malaysian cousin P. hebe chersonesus in having a broad black border on the hindwing. Beneath, the Plain Nawab has a large, pale silvery-green median patch covering about a quarter of the wing. The broad wing borders are mainly brown to dark brown in color.

Another Plain Nawab found perching on a leaf in a hill park

A Plain Nawab perching on a leaf with open wings.

Field Observations of Butterfly Behaviour: The adults are medium-sized, heavy-bodies butterflies with rapid, strong and sometimes erratic flights. It has a habit of perching high on a spot in a tree, and keeps returning to the same perch after making swift flights in the vicinity to chase intruders away. The adults have also been observed to puddle on wet ground, carrion, faeces and tree sap. Plain Nawab is relatively common and widely distributed in Singapore, with frequent sightings made in both the nature reserves and Southern Ridges.

A Plain Nawab feeding on tree sap

A Plain Nawab puddling on wet ground in the nature reserves

Early Stages:
The early stages of the Plain Nawab have been locally observed to feed on leaves of three plants in the Leguminosae family. Of the three, the Red Saga is most popularly utilized with regular sightings of caterpillars on young saplings in Southern Ridges where the plant is commonly planted. Red Saga can grow to a rather large tree. Its leaves are bipinnate, with 3 to 6 pairs of side stalks, and 9 to 15 leaflets on each side stalk. The seed pods are curved and scarlet seeds.

Host plant : Adenanthera pavonina

A mating pair of the Plain Nawab

The eggs of the Plain Nawab are laid singly on the leaf surface (usually on undersides) on a sapling of the host plant. Typically several eggs can be found on the same sapling, but usually on different side stalks of leaflets. Each egg is yellow and globular, with a slightly flattened top and indications of vertical ridges. The diameter is 1.4mm-1.5mm.

A mother Plain Nawab laying an egg on Red Saga in a hill park.

Left: fresh egg; Right: mature egg with a glimpse of the head capsule
The egg takes 4 days to hatch, and the newly hatched has a body length of about 3-3.5mm. The young caterpillar eats the entire egg shell as its first meal. Its body is initially creamy yellow but turning green a day or two later. It has a black head with 2 pairs of horns, the lower of which being shorter and straight, and the upper one being longer and curved. There is also pair of biege anal processes. Between feeds, the young caterpillar rests along the midrib near the leaf tip on the upperside. From this "base camp", the caterpillar ventures out to feed on nearby leaflets. Larger caterpillars in later instars spin a silk mat across several leaflets in order to provide a sufficiently large "base" on which to rest.

Two views of a newly hatched Plain Nawab caterpillar, length: 3.5mm

Left: Two Plain Nawab caterpillars (in early 1st instar) sighted resting on the upper surface
of Red Saga leaves in the Southern Ridges.
Right: A close-up view of one caterpillar in the left panel.

After 4-5 days of feeding, the 1st instar caterpillar grows to a length of about 6.5-7mm. The caterpillar stays dormant in its base camp with the new head capsule growing progressively larger behind the current one. The caterpillar moults to the next instar about half a day later.

1st instar caterpillar, late in this stage, length: 6mm.

Besides the increase in size, in particular the head capsule, the 2nd instar caterpillar has similar appearance as the 1st instar caterpillar. After five days in this instar, and having the body length increased to about 12mm, the caterpillar moults again.

Newly moulted 2nd instar caterpillar with old head capsule nearby, length: 6.5mm

A 2nd instar Plain Nawab caterpillar resting in its "base camp" on the upper surface
of a Red Saga leaf in the Southern Ridges.

The head capsule of the 3rd instar caterpillar is pale yellowish brown with wide vertical streaks in dark brown. The pair of anal processes has become shorter in length and prominence. Light yellowish stripes fringes the body just below the spiracles on the abdominal segments. This instar takes 4 to 5 days to complete with body grown to about 16-17mm in length.

Three views of a 3rd instar caterpillar, length: 15mm

The head capsule of the 4th instar caterpillar is yellowish green with two pairs of stripes in darker green. This instar lasts a further 8-9 days with body length reaching about 25-26mm. In the last few days of the instar, pale green crescent marks start to appear on each body segment, giving us a hint of what the next instar will bring.

Upper left: late 3rd instar; Lower right: newly moulted 4th instar;
Right: head capsule of the 4th instar caterpillar

Two views of a 4th instar caterpillar, length: 23mm

A late 4th instar Plain Nawab caterpillar resting on a "base camp" built from joining several
adjacent leaves of the Red Saga. Found in the Southern Ridges.

The 5th instar caterpillar closely resembles the 4th instar. The most noticeable change is the silvering green crescent marks which stand in stark contrast to the dark green base color. The pair of anal processes is so small that the anal segment takes on a near rectangular outline.

5th instar caterpillar, newly moulted, length: 22mm

5th instar caterpillar, late in this stage, length: 48mm

Head capsule of the 5th instar caterpillar

The 5th instar lasts for 10-13 days, and the body length reaches up to 48-50mm. Toward the end of this instar, the body gradually shortens in length. The fully grown caterpillar soon abandons its "base camp" and goes in hunt for a pupation site. Eventually the caterpillar comes to rest on a spot on the under surface of a stem. There it spins a silk pad to which it attaches its claspers (anal prolegs). The pre-pupatory larva then hangs vertically, typically with its body curled up.

A pre-pupa of the Plain Nawab in its curled up posture

Pupation takes place a day later. The pupa suspends itself from the same silk pad but now with its cremaster. The pupa has a berry like appearance with its thick and cylindrically oval shape. It is green but streaked with abundant white and features a broad head. Length: 17-19mm.

A time-lapse sequence of the eclosion event for one Plain Nawab caterpillar

Three views of a berry like pupa of the Plain Nawab.

The pupal period lasts for 9 days, and the pupa turns dark to reddish brown the night before eclosion. The large pale green patches on the forewings also become visible through the pupal skin at this stage.

Three views of a mature pupa of the Plain Nawab.

Eclosion takes place the next morning. The pupal case first cracks open with the adult butterfly making its way out. It quickly turns around and perches on the underside of the pupal case to "dry" and expand its wings. A few hours later, the adult butterfly makes the first flight of its life.

A time-lapse sequence of the eclosion event for one Plain Nawab caterpillar

A newly eclosed Plain Nawab

References:

The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society.
The Butterflies of Hong Kong, M. Bascombe, G. Johnston, F. Bascombe, Princeton University Press 1999

Text by Horace Tan, Photos by Benedict Tay, Khew SK and Horace Tan

Butterfly of the Month - February 2009

Butterfly of the Month - February 2009
The Commander (Moduza procris milonia)

For the month of February 2009, which also happens to be the month of the year on which my birthday falls, we feature a species which I had used as my avatar and nickname/alter ego in ButterflyCircle - The Commander. I'd chosen this butterfly as my nickname as I had fond memories of chasing this strange-looking and new butterfly that I'd never seen before when I was a school-going kid in Malaysia. I still remember vividly the encounter at the forested area of Gasing Hill in Petaling Jaya. The Commander had flown and landed on the surface of a leaf in front of the forest path where I was walking, and for a moment, both of us froze. As I admired the colour and pattern of the wings, I took a step closer and the movement startled the skittish butterfly and it took off at turbo speed to the treetops, ending the short encounter, but the image of this beautiful butterfly was imprinted in my mind.

It was only after the outing when I came back home to check on my reference books, that I knew what I had seen. It was some years later before I encountered this elusive beauty again.

The Commander (Moduza procris milonia) is the sole representative of the genus in Malaysia and Singapore. It is related to the "Admiral" species under the genus Limenitis in the temperate regions. Indeed, the species, together with a number of other closely related genera, has been re-classified under the sub-family Limenitidinae.

The Commander is dark reddish brown on the upperside with the wings traversed by a broad white macular band extending to both the fore and hindwings. There are four white subapical spots on the forewings. The wing borders are strongly crenulated. Each hindwing has two series of black submarginal and postdiscal spots. The underside is marked as above, but the basal halves of the wings are pale greenish grey in contrast to the orangy brown on the upperside. Males and females are similar in appearance.

In Singapore, the species is often observed singly, flying rapidly and stopping to sunbathe with its wings open flat on the upper surfaces of leaves. It has a strong and determined flight, is skittish, and takes off to the treetops if it senses any danger. Females are occasionally seen in the vicinity of its preferred host plant, Timonius wallichiana, as she tries to oviposit. The early stages of the Commander has been recorded by Horace Tan, and is found on this blog here.

Occasionally, a cooperative individual is encountered, either puddling at roadside seepages, or when it decides to forage for food amongst fallen leaves or amongst low shrubbery. However, it is always on the move, and photographing this species is not the easiest as far as butterfly photography is concerned. It is partial to human perspiration, and depending on whether the butterfly is hungry or not, a lucky individual may be entertained with a friendly close-encounter with a Commander, when it decides to feed.

A hungry Commander feeds on my sweaty tripod ballhead

The Commander is moderately common, and frequents the forested areas of the nature reserves as well as public parks and gardens.

Text by Khew SK : Photos by Benedict Tay, Horace Tan & Khew SK

Life History of the White Four-Line Blue

Life History of the White Four-Line Blue (Nacaduba angusta kerriana)

Butterfly Biodata:
Genus: Nacaduba Moore, 1881
Species: angusta H. Druce, 1873
Subspecies: kerriana Distant, 1886
Wingspan of Adult Butterfly: 30mm
Caterpillar Local Host Plants: Entada spiralis (Fabaceae)

A female White Four-Line Blue perching on a leaf near its host plant in between oviposition visits

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 purplish blue with a thin black border, about 1mm broad towards the apex; the female has broad black border on the forewing and a light blue ground colour with diffuse greyish markings on both wings. Beneath, both sexes has greyish ground colour with very broad and diffuse whitish-grey stripes. On each hindwing, there is an orange-crowned tornal spot lightly speckled with bluish-green metalic scaling. i 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 whitish bacground. The prominent rounded black sub-marginal spot in space 6 of the hindwing serves as an important identification key for this species.

A male White Four-Line Blue perching on a branch

A male White Four-Line Blue perching another branch

A sunbathing male White Four-Line Blue showing its upperside

Field Observations of Butterfly Behaviour:
Though included in the early authors' checklists for Singapore, this species has eluded the local butterfly enthusiasts in recent years before its recent re-discovery in the December 2008. Sightings have been confined to a single location where its host plant is thriving at tree top levels. The adult has an erratic flight, and typically makes its appearance in sunny weather. Encounters usually take place in sunlit spots with the adult sunbathing or flitting from perch to perch in the vicinity of its host plant.

Early Stages:
The host plant, Entada spiralis, is a woody climber with bipinnate leaves, usually with 4 pairs in a pinna. Flowers are small and occur in dense racemes. Seed pods are curled with 5-11 very large seeds to each pod. This tree-topping vine can be found in the Central Catchment Nature Reserves as well as in the Southern Ridges. Besides the White Four-Line Blue, locally this plant also plays host to the Large Four-Line Blue (Nacaduba pactolus odon), Common Line Blue (Prosotas nora superdates) and the Common Grass Yellow (Eurema hecabe contubernalis). The early instars of the White Four-Line Blue feed on young leaves of this plant by grazing away the upper layer of lamina. The later instars nibble away the lamina from the leaf edge, as well as the outer layer of young stems.

Host plant : Entada spiralis

Young shoots of Entada spiralis.

A mating pair of White Four-Line Blue

A mother White Four-Line Blue making an oviposition visit to young shoots of E. spiralis.

Eggs are laid on the young shoots of the host plant, typically in spaces between very young and yet to be unfurled leaves. It is not uncommon for a number of eggs to be found on the same shoot, however the eggs occur singly rather than in clusters. Each egg is pale yellowish green, circular and has a depressed micropylar area. The surface is criss-crossed with numerous tightly-spaced lines. Each egg has a diameter of about 0.4mm.

Two eggs of the White Four-Line Blue. Diameter: 0.4mm.

It takes 2-3 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 also changes gradually to a brighter shade of yellow. A diamond-shaped pro-thoracic shield and a slight depression on the anal segment can be distinguished easily through contrasting and darker shades of coloration.

1st instar caterpillar, late in this stage. Lengths: 1.5mm (top) and 1.2mm (bottom)

The first instar lasts for 2 days and the body length reaches about 1.5mm before the moult to the 2nd isntar. The long dorsal setae are absent in the 2nd instar caterpillar. The body color is mainly yellow with a greenish undertone. The prothoracic shield is less prominent, being slightly paler than the yellow base color. The 2nd instar also lasts for 2 days and the caterpillar grows to a length of about 3m to 3.5mm.

2nd instar caterpillar, freshly moulted to this instar, length: 1.5mm

2nd instar caterpillar, late in this stage. Lengths: 2.5mm (top) and 3mm (bottom).

The 3rd instar caterpillar is still yellowish green but with an increasing emphasis in green. Faint markings in much paler yellow appear on both sides of the dorsal line. After 2 days in this stage with the body length reaching a maximum about 6-7mm, the next moult takes place to bring the caterpillar to its final instar.

3rd instar caterpillar, Lengths: 3.5mm (top) and 4.5mm (bottom)

3rd instar caterpillar, late in this stage, length: 6mm

The 4th instar caterpillar initially resembles the 3rd instar caterpillar in the day prior to the moult. However as it proceeds to feed and grow in this final instar, the body quickly takes on a much lighter shade of green with the whitish dorsal-lateral shadings more prominent than in the 3rd instar. The prothorcic shield is whitish with a few brown spots, and the dorsal nectary organ and ventacular organs are distinguishable on the posterior segments.

4th instar caterpillar of lengths: 8mm (top) and 11mm (bottom).

Body features of a 4th instar caterpillar. Left: dorsal nectary organ (DNO) and tentacular Organ (TO).
RIght: prothoracic shield.

The 4th instar lasts for 4 days and the body grows up to a length of about 11-12mm. On the last day of this stage, the caterpillar ceases food intake and its body shrinks in length. It wanders around for almost a full day before it comes to rest on a spot among leaves for pupation. The pre-pupatory caterpillar prepares for pupation by spinning silk threads to shape the leaves into a pupation shelter. Within the tight interior of the shelter, the pre-pupatory caterpillar stations itself with silk girdles and the attachment of the cremaster.

Two views of a pre-pupa of the White Four-Line Blue

The next day, after 9-10 days of larval growth, pupation finally takes place. The pupa has the typical lycaenid form, and is 8-9mm in length. It is mostly pale brown and speckled with black spots of various sizes and shapes.

Two views of a fresh pupa of the White Four-Line Blue

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 upal skin. The next day the adult butterfly emerges from the mature pupa.