27 August 2009

Life History of the Blue Spotted Crow

Life History of the Blue Spotted Crow (Euploea midamus singapura)

Butterfly Biodata:
Genus: Euploea Fabricius, 1807
Species: midamus Linnaeus, 1758
Subspecies: singapura Moore, 1883
Wingspan of Adult Butterfly: 80mm
Caterpillar Local Host Plant: A plant in the Apocynaceae family, specific ID to be determined.

Physical Description of Adult Butterfly:
Above, the wings are blackish brown, usually without the blue sheen seen in other Euploea species. The termens are slightly crenulate and there are marginal and submarginal series of white spots, with submarginal spots in spaces 6, 7 and 8 rather large and elongated. on the forewings. There is also a white spot in the cell and a few distal spots. Underneath, the markings resemble those on the upperside. The male has a small and narrow brand in space 1b on the forewing and a pale yellowish scent patch in the cell area on the hindwing.

A Blue Spotted Crow feasting on the flowers of a Syzygium plant in the nature reserve.

A Blue Spotted Crow puddling on the cement floor of a shelter hut in the nature reserve.

Field Observations of Butterfly Behaviour:
This Singapore subspecies of the Blue Spotted Crow is uncommon in Singapore, and is rarely seen. Sightings of the slow flying adults includes individuals or small groups visiting flowers and puddling. One rare occasions, several adults could be seen flying around shelter huts built alongside trails in the catchment area, with some even puddling on the cement floor of the shelters. Although mostly confined to the nature reserves, some individuals have also been observed in housing estates.

Early Stages:
Elsewhere in its range of occurrence, host plants recorded for this species are mainly members of the Apocynaceae family, examples are Strophanthus divariatus and S. divergens in Hong Kong, S. dichotomus, Nerium oleander and Roupellia sp. in Java. As for the singapura subspecies of the Blue Spotted Crow, thus far only one host plant, which has opposite leaves and pale yellowish sap (lactiferous), has been located in the local nature reserves. The caterpillars of Blue Spotted Crow feed on the young and tender leaves in its early instars but move on to the more mature and larger leaves in the later instars.

Local host plant for the Blue Spotted Crow found in the nature reserve.

The eggs of the Blue Spotted Crow are laid singly on the young leaves of the host plant, typically on the underside. The yellow eggs are tall (about 1.8mm in height) and somewhat cylindrical (diameter: 1mm) with a rounded top. The egg surface is ribbed.

A mother Blue Spotted Crow laying egg on a young leaf of the host plant.

Left: fresh egg; Right: mature egg. Note the black head is visible in the mature egg.

The egg takes about 3 days to hatch. The young caterpillar emerges by eating away part of the egg shell. The rest of the egg shell becomes the first meal for the newly hatched, which has a length of about 2.3mm. Its cylindrical body is pale yellowish. The large head capsule is black in color. A pair of short and inconspicuous protuberances can be found on the dorsum of each of the following four segments: 2nd and 3rd thoracic segments, 2nd and 8th abdominal segments.

Two views of a newly hatched caterpillar eating the egg shell, length: 2.3mm.

Once the newly hatched moves on to feed on the young leaves over the next few hours, its body starts to take on a green undertone. The growth is rather rapid with the body length doubling in one day, and after just 1 to 1.5 days from hatching, it moults to the 2nd instar. Towards the final hours of the 1st instar, the 8 protuberances turned orangy brown and become more marked in appearance. This period of growth also brings along blackened ends for all 8 pairs of legs.

Two views of 1st instar caterpillar, late in this stage, length:5.5mm.

The body of the 2nd instar caterpillar is again yellowish orange with a green undertone. The most obvious change is the lengthening of the 8 protuberances to short processes, each of which is almost entirely dark brown to black. There are two small brown spots on the dorsum of the prothorax, and one large black patch on the posterior end of the body. This instar lasts only 1 to 1.5 days with the body length reaching 11mm before the moult to the 3rd instar.

Two views of a 2nd instar caterpillar, late in this stage, length: 11mm

The 3rd instar caterpillar is similar in appearance to the 2nd instar caterpillar with the only change being the proportionally longer processes. This instar takes about 1-1.5 days to complete with body length reaching about 16-17mm.

3rd instar caterpillar, newly moulted, length: 6mm

3rd instar caterpillar, late in this stage. .Lengths: 9mm (top) and 11mm (bottom).

Retaining very much the same body features from the earlier two instars, the 4th instar caterpillar distinguishes itself in having proportionally longer processes which have the tendency to flex forward with ends slightly curved. This instar lasts 1.5 to 2 days with the body length reaching about 27mm.

Two views of a 4th instar caterpillar, late in this stage, length: 27mm.

The 5th and final instar brings along a slightly more dramatic change in appearance. Now the 8 processes have become very long and filamentous, with the tapering ends having a strong tendency of twirling. The spiracles have also become more prominently marked in large black spots.

A newly moulted 5th instar caterpillar, with its exuvia trailing behind.

One surprising and exciting find during this breeding exercise is the discovery of adenosma being present in this Euploea species, a first for the Danainae subfamily. The Blue Spotted Crow caterpillars, at least for the singapura subspecies, readily flash their adenosma when they are disturbed. This yellow-colored adenosma could be easily observed in both the 4th and 5th instars. Refer to the pictures and youtube clip below for an illustration of this adenoma, which is located just ahead of the 1st pair of the thoracic legs. As can be seen in the pictures, the caterpillars of Blue Spotted Crow also adopt the characteristic on-guard posture with the anterior body arched and the head tucked beneath the thorax.

The on-guard stance of an early 5th instar caterpillar, length: 30mm.

The same caterpillar as in the earlier picture, this time with its adenosma everted.

The eversion of the adenosma of a 4th instar caterpillar of the Blue Spotted Crow.

Two views of a 5th instar caterpillar, length: 40mm.

The 5th instar lasts for 4-5 days, and the body length reaches up to 47mm. On the last day, the caterpillar ceases feeding, and its body becomes shortened but with no change in body color. It wanders around in search of a pupation site. Typically it comes to a halt on a branch/stem or a leaf underside, where the caterpillar spins a silk pad from which it soon hangs vertically to take on the pre-pupatory pose. Within the few hours prior to pupation, the caterpillar gradually relaxes and lengthens to a straight posture. Waves of contraction soon travel from the the rear end to the head until the pupation event kicks in.

Pre-pupatory larva. Left: early stage; Right: late stage with the onset of pupation only minutes away.

The pupation event of a Blue Spotted Crow caterpillar (shown at 10x speed).

Pupation takes place 0.5 days after the caterpillar assumes the hanging posture. Typical of the pupae within the Nymphalidae family, the pupa of the Blue Spotted Crow suspends itself from the silk pad with no supporting silk girdle. Initially, the pupa is bright yellowish orange, but the surface gradually takes on a silvery metalic glitter about a day later. The pupa is rather rotund, and has a few black spots and dark brown patches on the dorsum. Length of pupae: 20-22mm.

Three views of a fresh pupa of the Blue Spotted Crow.

Three views of a shining pupa of the Blue Spotted Crow.

Three views of a mature pupa of the Blue Spotted Crow.
The prominent submarginal spots can be seen in the wing pad area.

After about 6 days of development, the pupal skin turns translucent as the development within the pupal case comes to an end. The spots on the forewing upperside also become discernible. The following day, the adult butterfly emerges from the pupal case. It then perches nearby to expand and dry its wings before taking its first flight.

A newly eclosed Blue Spotted Crow drying its wings on its pupal case.

A newly eclosed Blue Spotted Crow.

  • The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, The Malayan Nature Society.
  • A Photographic Monograph on Hong Kong Butterflies, Volume 1, Hong Kong Lepidopterists' Society.
  • Butterflies of Thailand, Pisuth Ek-Amnuay, 1st Edition, 2006
Text by Horace Tan, Photos by Anthony Wong, Henry Koh and Horace Tan

22 August 2009

Two Minds, One Theory

Two Minds, One Theory
Wallace & Darwin - The Two Faces of Evolution Theory

As part of the year-long events celebrating the 150th Anniversary of the Singapore Botanic Gardens, the exhibition on the Evolution Theory, first discussed by Charles Darwin and his lesser-known counterpart, Alfred Russel Wallace is currently being featured at the Botany Centre of the SBG.

The exhibition discusses Natural Selection and the Theory of Evolution as first postulated by the two intellectuals after spending a lot of time circumnavigating the globe and observing a profusion and diversity of life forms. The search for an explanation to understand long-term organic change brought them to many parts of the world then unfamiliar with the western civilisation.

Between the two intellectuals, A.R. Wallace spent many years in the Far East, collecting thousands of specimens in his research. In 1869, he published his landmark work, the Malay Archipelago, elaborating his theory of evolution. Wallace also made significant contributions to biogeography when he linked the geographical distribution of animals and plants to the regions' geological history.

Alfred Russel Wallace (1823-1913) - Ardent beetle & butterfly collector, naturalist, biologist, socialist, prolific Victorian writer, biogeographer and thinker

Whilst in Singapore, Wallace explored Bukit Timah collected 700 species of beetles. The incredible productivity at Bukit Timah is an illustration that we live in a region with one of the richest biodiversities in the world.

Amongst his collections, Wallace also collected numerous species of butterflies in the region. As a collector and a scientist, Wallace wrote in his book, the Malay Archipelago, a rather graphic and emotional account after successfully capturing the spectacular Wallace's Golden Birdwing (Ornithoptera croesus) at Batchian, Moluccas in 1858.

He noted that "On taking it out of my net and opening the glorious wings, my heart began to beat violently, the blood rushed to my head, and I felt much more like fainting than I have done when in apprehension of immediate death. I had a headache for the rest of the day. So great was the excitement produced by what will appear to most people a very inadequate cause".

Wallace's Golden Birdwing (Ornithoptera croesus) Male (above) and female (below) Plate from Reise Fregatte Novara. Zoologischer by Rudolf Felder and Alois Friedrich Rogenhofer

Wallace is also credited with describing many butterfly species for the first time, and amongst those was the famous Rajah Brooke's Birdwing (Trogonoptera brookiana) which Wallace first described in 1855.

Wallace is credited with first describing the famous Rajah Brooke's Birdwing in 1855 after a specimen was given to him by the then governor of Sarawak, James Brooke.

In recognition of his work, many later researchers also paid tribute to Wallace by naming new organisms after him. Amongst butterflies, one famous local subspecies of the Blue Pansy is the most well-known. The Blue Pansy (Junonia orithya wallacei) had the subspecies named after Wallace by the collecter Distant in 1883.

The local subspecies of the Blue Pansy was named after Wallace

The SBG Exhibition traces some of Wallace's journey in the Far East, and explains some of his theories and findings. Interestingly, he is also credited with giving the Durian, the name "King Of Fruits"! He was a converted durian eater, and actually enjoys eating the fruit that many westerners avoid.

Some of Wallace's theories on natural selection, displayed in butterflies, are mimicry, camouflage, masquerade, sexual dimorphism and so on, can be seen in Singapore's butterflies. At the SBG exhibition there are also many specimens of butterflies around the displays and nature dioramas.

At the Launch of the Exhibition, I also gave a short talk on Natural Selection, adaptation and survival strategies with particular reference to butterflies. I was honoured to have, amongst the distinguished guests in the audience, personalities like Minister George Yeo, Professor Tommy Koh and nature guru, Ms Ilsa Sharp.

The exhibition lasts until 31 Aug 2009, and for those who have yet to catch this exhibition in tribute to Alfred Russel Wallace, you have about a week more to visit the display at the SBG Botany Centre.

Text & Photos by Khew SK (except where indicated)

15 August 2009

Life History of the Elbowed Pierrot

Life History of the Elbowed Pierrot (Caleta elna elvira)

Butterfly Biodata:
Genus: Caleta Fruhstorfer, 1922
Species: elna Hewitson, 1876
Sub-species: elvira Fruhstorfer, 1918
Wingspan of Adult Butterfly: 22mm
Caterpillar Local Host Plants:
Ziziphus sp. (Rhamnaceae)

Physical Description of Adult Butterfly:
Above, the Elbowed Pierrot is dark brownish black with a broad white band spanning both wings. Beneath, the Elbowed Pierrot is yellowish white with a number of black spots and markings. In particular, the basal streak in the forewing is right-angled, and appears to link up with the basal streak in the hindwing. Each hindwing has a slender white-tipped filamentous tail at the end of vein 2.

An Elbowed Pierrot visiting flowers in the nature reserve.

An Elbowed Pierrot puddling on wet grounds.

An Elbowed Pierrot resting on a perch.

Field Observations of Butterfly Behaviour:
This small-sized species is rather common in the nature reserves of Singapore. The adults are often found flying close to the ground and settled at moist spots on the forest floor. On sunny days, they can be found to visit flowers, and the males have been observed to puddle on bird droppings.

Early Stages:

The local host plant, a Ziziphus sp., is a thorny straggling shrub with simple, alternate and ovate-lanceolate leaves, each of which has three prominent nerves and finely toothed along the edge. Young leaves are light brown to reddish brown, and turning green when mature. All four instars of the immature stages of the Elbowed Pierrot feed on the young brownish leaves, and the green leaves when they are still relatively young and tender.

Host plant:a Ziziphus sp. Young shoots.

Host plant: a Ziziphus sp. Close-up shots of young and mature leaves.

A mating pair of the Elbowed Pierrot.

Elbowed Pierrot mothers' attempts to lay eggs on the leaves of the host plant.

Eggs of Elbowed Pierrot are typically laid on young shoots or leaves of the host plant. The small egg is disc-like (about 0.5mm in diameter) with a depressed micropylar. When freshly laid, the egg is yellowish green. The color soon decolorizes to light green within the next few hours, and then to white overnight as it matures. The surface is covered with a reticulated pattern of intersecting ridges.

Two views of an egg of the Elbowed Pierrot. Diameter: 0.5mm.

Left: mature egg showing the caterpillar eating away the egg shell for its exit.
Right: empty egg shell.

Each egg takes 2-2.5 days to hatch. The young caterpillar emerges after nibbling away sufficiently large portion of the egg shell. Measured at a length of about 0.9mm, its pale yellow body is cylindrical in shape, sporting long fine setae (hairs) and a brown head capsule.

Top: a newly hatched caterpillar, length: 0.9mm.
Bottom: 1-day old caterpillar, length: 1.2mm

The newly hatched grazes on the surface of young leaves. As it feeds and grows, its body takes on a greenish undertone. After 2 to 3 days of growth, it looks pumped up at a length of about 2mm. After a period of immobility of about half a day, it moults to the 2nd instar.

1st instar caterpillars. Top: 2-day old, length: 1.5mm.
Bottom: late in this stage, length: 2mm.

Covered with numerous setae, the body of the 2nd instar caterpillar could in either light yellowish green or pale pinkish coloration. Setae found at the dorsal and lateral margins are longer and stiffer. The body is flatter compared to the 1st instar caterpillar, and faint dorsal bands whitish in color are discernible.

2nd instar caterpillars. Top: newly moulted, length:2mm.
Bottom:late in this stage, length: 3.5mm.

Top: late 2nd instar in pre-moulting dormant state.
Bottom: newly moulted 3rd instar caterpillar.

The 2nd instar caterpillar reaches a length of about 3.5-4mm, and after about 3 days in this stage, it moults again. The 3rd instar caterpillar has numerous short and fine body setae. The two whitish parallel dorsal bands, flanked by two thin and deep green bands, are now rather pronounced, The 3rd instar takes 3-4 days to complete with the body length reaching about 6.0-7.0mm. There is no obvious sign of any nectary organs, which are common in many other lycaenid species, on the 7th and 8th abdominal segments,

3rd instar caterpillars. Top: early in this stage, length: 4mm.
Bottom: late in this stage, length: 6mm

The 4th (and final) instar caterpillar is similar in appearance to the 3rd instar caterpillar with one main difference being the apparent merging of the two dorsal bands into a single broad band. The body segments appear to be translucent, in either light green or pale pinkish coloration. The body shape deviates from the usual onisciform shape in being much flatter with a large prothorax.

4th instar caterpillars. Top: middle-aged, pink form, length: 9.5mm.
Bottom: late in this stage, green form, length: 12mm.

While some members of the Caleta genus (such as Caleta roxus) do not carry any nectary organs in any instar, the Elbowed Pierrot has a slit-like structure on the 7th abdominal segment in the final instar. With no ant attendance observed in the field, it is likely to be a non-functional dorsal nectary organ. In addition, no tentacular organs can be found on the 8th abdominal segment.

A likely non-functional dorsal nectary organ on the 7th abdominal segment of
a final instar Elbowed Pierrot caterpillar.

After 5-6 days of growth and reaching a maximum length of around 12-13mm in the final instar, the body of the caterpillar gradually shrinks, and finally takes on a pale reddish brown coloration. All bred specimens chose to enter their pre-pupatory phase on a spot on the leaf surface. At the chosen site, the caterpillar readies itself for pupation by spinning a silk girdle and a silk pad. The caterpillar secures itself to the silk pad via claspers on its posterior end.

Two views of an immobile pre-pupatory larva of the Elbowed Pierrot.
The silk girdle can be easily seen.

Early stages of the Elbowed Pierrot.

Pupation takes place after one day of the pre-pupal stage. The hairy pupa has the typical lycaenid shape, being somewhat flatter and having a broader abdomen. It is pale brown in the abdomen, dark brown on the thorax and beige in the wing pad areas. The pupa has a length of about 8-9mm.

Two views of a pupa of the Elbowed Pierrot, length: 8mm

Six days later, the pupa becomes darkened in color signaling the imminent emergence of the adult. The prominent white bands on the forewing uppersides become visible through the pupal skin in the wing pads. The next day the adult butterfly emerges from the mature pupa

Two views of a mature pupa of the Elbowed Pierrot.

A newly eclosed Elbowed Pierrot

A newly eclosed Elbowed Pierrot perching near its empty pupal case.

  • The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, The Malayan Nature Society.
  • The life history of Caleta roxus, Konrad Fiedler, Nachr. entomol. Ver. Apollo, N.F. 14 (4): 371-384, Jan. 1994.

Text by Horace Tan, Photos by Anthony Wong, Benedict Tay, Sunny Chir and Horace Tan