30 January 2010

Life History of the Two-Spotted Line-Blue

Life History of the Two-Spotted Line Blue (Nacaduba biocellata)

Butterfly Biodata:
Genus: Nacaduba Moore, 1881
Species: biocellata C. & R. Felder, 1865

Wingspan of Adult Butterfly: 17 mm
Caterpillar Local Host Plants:
Acacia auriculiformis (Leguminosae, common name: Earleaf Acacia, Black Wattle), Acacia mangium (Leguminosae, common name: Silver Wattle).

A Two-Spotted Line Blue checking out flowers of mile-a-minute in a hill park.

Another Two-Spotted Line Blue on a perch under the midday sun.

Physical Description of Adult Butterfly:
Upperside, the male is lilac with dark blue basal area while the female is dull brown with varying degree of blue in the basal area. Both sexes have two brown-black subtornal spots on the hindwing. Underside, both sexes are similarly marked. The forewing is pale orange-brown in base colour with a short band at cell-end, and a longer post-discal band, both of which are narrowly edged with brown and white. The hindwing is pale brown in base colour with a series of brown spots and bands narrowly edged with darker brown and white, and two black subtornal spots with a few iridescent green scales and ringed with pale yellow-brown.

A Two-Spotted Line Blue perching on flower buds of Acacia mangium.

A Two-Spotted Line Blue visiting flowers.

Field Observations of Butterfly Behaviour:
This species is Indo-Australian in origin, and was recently discovered in Singapore (see this BC blog article for details). Sightings of the tiny but usually restless adults have typically been in the vicinity of its local host plants, visiting flowers on nearby flowering shrubs or herbs. Both sexes have also been sighted, at times in large numbers, flying around or perched on inflorescence or foliage of the flowering host plants. In flight, they can easily be mistaken as other similarly-sized line blues. A definite identification can only be made when the butterfly comes to rest and allows its two trademark hindwing subtornal spots to be observed.

A Two-Spotted Line Blue perching on flower buds of Acacia auriculiformis.

A Two-Spotted Line Blue resting on a perch.

Early Stages:

In its homeland, Australia, Two-Spotted Line Blue (TSLB) is known to be utilizing a wide range of Wattles as larval food plant. In Singapore, an invasive and naturalized Wattle, Acacia auriculiformis (the Black Wattle), is thus far the only recorded host plant. The following account of the life history of this recent addition to our checklist is based on observations made of 20 plus specimens, in varying stages of development, taken from one local host plant in two visits within a week. Another local Acacia plant, A. mangium, is listed as a host plant for TSLB in Australian literature. Hence our bred caterpillars had no problem consuming its flower buds when introduced. Caterpillars of TSLB feed on both flower buds and blossoming flowers of the host plants.

Host plant: Acacia auriculiformis.

Host plant: Acacia mangium.

Eggs of Two-Spotted Line Blue are laid singly near a flower bud on an inflorescence of the host plant. Each egg is disc-like (about 0.4mm in diameter) with a depressed micropylar. The surface is covered with a reticulated pattern of intersecting ridges and pits of varying sizes. When freshly laid, the egg is pale green. The color turns to white as the egg matures.

A mating pair of the Two-Spotted Line Blue.

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

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 0.7mm to 0.8mm, its pale yellow body is cylindrical in shape, wider at the anterior, and sporting two rows of long dorsal setae, and moderately long sub-spiracular setae. The head capsule is dark brown or black in color.

Two views of a new hatched caterpillar, length: 0.7-0.8mm.

The newly hatched makes its way to a nearby flower bud and starts to munch on it. After about 2 days of growth, it reaches about 1.2mm in length and looks rather fattened. Its tiny size, matching coloration and its resting posture on the small flower buds makes it difficult for any casual observer to notice its presence.

A late 1st instar caterpillar on a flower bud, dormant prior to its moult to the next instar.
Length: about 1mm.

Still sporting the two rows of dorsal setae and sub-spiracular setae, the 2nd instar caterpillar now has numerous and very short setae covering its body surface. Its body colour is pale yellow with a green undertone. Dorsally, the body features a hump, wider at the anterior, and the two rows of dorsal setae essentially line the edges of this hump. The head capsule is still dark brown to black in colour. The growth in this stage brings the caterpillar to a length of about 2.5mm, and after about 2 days in this stage, it moults again.

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

The 3rd instar caterpillar does not have the two rows of long dorsal setae as in the previous two instars. The sub-spiracular setae are still present but rather short. The dorsal hump is now marked with paler patches along the two side edges, giving the impression of a green dorsal band on the ridge of the hump. Both the dorsal nectary organ and the tentacular organs are discernible in this instar. The 3rd instar takes 2.5-3 days to complete with the body length reaching about 4-4.5mm before the next moult. In the hours leading up to the moult, a number of brown markings, which will be featured strongly in the early part of the next instar, become visible on the body surface.

Two views of a 3rd instar caterpillar, length: 4mm.

3rd instar caterpillars. late in this stage, prior to moulting, length: 4mm.
Note the appearance of brown markings.

The 4th (and final) instar caterpillar has a number of brown markings on the whitish patches marking the two side edges of the dorsal hump, and more such brown markings in the sub-spiracular white patches. Brown lateral patches are found on the 1st abdominal segment. There is also a dorsal brown patch on 8th abdominal segment. The diamond-shaped prothoracic shield is white in color and embedded within a brown patch covering the entire dorsum of the prothorax. The head capsule is brown in colour. The nectary organs are rather prominent in this instar and the everted tentacular organs can be rather long (up to 1.5mm) and spectacular. See the attached youtube video (near the end of this article) of such a display.

Two views of a 4th instar caterpillar, length: 5.5mm.

As it eats and grows to a length of up to about 9.5mm (majority has a maximum length of about 8.5mm) within 3-4 days, the dorsal and sub-spiracular brown markings fade gradually, and the white dorsal and sub-spiracular patches becomes more intense in coloration and take on a pale yellowish tone.

Two views of a 4th instar caterpillar, late in this stage, length: 9.5mm.

On the last day of the 4th instar, the caterpillar ceases its feeding activity. Its body colour changes drastically to two extreme colour forms. In the red form, the body is mostly iridescent red while the green form mostly iridescent green. Some individuals take on an intermediate form between the red and green forms. Of the batch of 20-odd caterpillars bred, the red forms dominates and account for about 80% of all pre-pupae. At this point, the movement of the caterpillar is rather rapid as it wanders around in search of a pupation site.

Three different examples lf very late final instar caterpillars, showing colour variations.

In the breeding environment, the caterpillar typically chooses the tight space in a curled up leaf or the space between two leaves in a pile of leaf litter. At the chosen site, the caterpillar readies itself for pupation by spinning silk threads to secure itself and partially sealing off access point to the pupation site.

Two views of an immobile pre-pupa of the Two-Spotted Line Blue, Red form.

Two views of an immobile pre-pupa of the Two-Spotted Line Blue, Green form.

Pupation takes place after one day of the pre-pupal stage. The pupa has the typical lycaenid shape, pale brown in base colour with darker brown spots and blotches which are highly variable in numbers and sizes. Unlike most other lycaenid pupae, the pupa of Two-Spotted Line Blue does not secure itself with cremastral hooks to any silk pad, and its posterier end does not angle downwards. Length of pupae: 5-7mm.

Two views of a pupa of the Two-Spotted Line Blue, length: 6mm

Four days later, the pupa becomes darkened in color signaling the imminent emergence of the adult. The next day the adult butterfly emerges from the mature pupa.

Two views of a mature pupa of the Two-Spotted Line Blue.

A newly eclosed Two-Spotted Line Blue near its empty pupa case, waiting for its wings to be firmed up.

Life History of the Two-Spotted Line Blue.

  • The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, The Malayan Nature Society.
  • Butterflies of Australia: Their Identification, Biology and Distribution, Volume Two, Michael F. Brady, CSIRO Publishing.

Text by Horace Tan, Photos by James Chia, Tan Ben Jin, Sunny Chir, Khew S K and Horace Tan

23 January 2010

An Aussie Skipperoo Comes to Town

An Aussie Skipperoo Comes to Town
Introducing the Yellow Palm Dart (Cephrenes trichopepla)

It took quite some time of careful research and breeding the entire life history of this species before ButterflyCircle members finally confirmed that this Hesperiidae, which is usually found in Northern Australia, is now a permanent resident of Singapore (and also Malaysia!)

This skipper, which superficially resembles the local Telicota species, escaped notice for many years. It all started (now that I've had time to dig out my notes and emails from various people) with an email from a butterfly expert from Australia who was on holiday in Singapore. This was back in 1999! Kelvyn Dunn, who wrote me an email later in 2003, said this :

"Recently in Singapore (1999) I observed and examined in the hand (incl photographed) an example of Cephrenes trichopepla (an Australian sp.) in Fort Canning Park. I have video images.

Have you found any evidence of this skipper species as yet? I presume mine was not athe only one. (I can send pics if you want to see them to examine it for yourself).

In Australia my claim has met some scepticism because I did not preserve the adult."

At that point in time, ButterflyCircle hadn't even re-discovered the Plain Palm Dart (Cephrenes acalle niasicus) yet, so I was rather skeptical at Kelvyn's find too. The many lookalikes amongst the Telicota and larger Potanthus spp. didn't help either, so I assumed that Kelvyn's find was probably another one of the Telicota and left it at that.

Some time later, more individuals of this rather large skipper turned out in various locations in Singapore - public parks, gardens, flower nurseries and so on. By then, we had confirmation of the existence of the Plain Palm Dart after a few shots of the more distinctive females were validated. Hence I assumed that what Kelvyn observed in 1999 was probably a male Cephrenes acalle.

Although the males of the Plain Palm Dart had more angular apical forewing area, the markings on the undersides are less distinct than this other strange skipper that had clean orange colours and crisp markings on the undersides. The physical appearance of this butterfly didn't really match the markings of any of the Telicota spp shown in the reference books on Malaysian, Singaporean and even Thai butterflies.

So we continued with the belief that this skipper could be just be displaying variations of the markings of the extant species of Telicota or the solitary Cephrenes sp in Singapore.

More shots turned up of this species, which we incorrectly identified as one of the Telicota spp. But the larger size of many of the individuals sighted continued to intrigue me, although I put it down to variations in the sizes of the Hesperiidae, which occurs quite often amongst some other species. Even after managing to capture a mating pair of this species, I left it that it was one of the Telicota.

A mating pair of the Yellow Palm Dart observed near a reservoir park

By good fortune and chance, ButterflyCircle member Anthony Wong discovered a caterpillar feeding on coconut leaf (Cocos nucifera) during a survey of the offshore island of Pulau Semakau. Left in the good hands of our expert caterpillar farmer, Horace Tan, photos of the caterpillar indicated a physical difference from the Telicota caterpillars as shown in various reference books. This caterpillar had unique orange-yellow "cheeks" on both sides of its mandibles.

Close up of the Yellow Palm Dart's caterpillar, showing its orange-yellow "cheeks"

A quick research on Internet resources found a closely-matched early stages of the Australian skipper, Yellow Palm Dart (Cephrenes trichopepla). Shortly before this find on Pulau Semakau, our ButterflyCircle member in Kuala Lumpur, LC Goh, had also recorded complete life history of a an unidentified species of skipper in March 2009. Comparing the photos with more of the caterpillars that were eventually bred in Singapore, it was confirmed that what LC Goh bred, was also a Yellow Palm Dart!

Caterpillar of the Yellow Palm Dart, bred by LC Goh in Kuala Lumpur, Malaysia

Further consultations with Kelvyn Dunn, who generously provided photos and research papers that he had written on two resident Cephrenes in Australia, and also our Malaysian expert lepidopterist, Dr Laurence Kirton, it is now established beyond doubt, that the Hesperiidae species, the Yellow Palm Dart (Cephrenes trichopepla) is now part of the butterfly fauna in Malaysia and Singapore.

Male and Female Yellow Palm Darts - freshly eclosed specimens from caterpillars bred on Cocos nucifera

Both sexes of the Yellow Palm Dart are almost identical in appearance. The uppersides of the wings are dark brown to black, with orange bands on the forewings, and a wide discal band on the hindwings. The undersides are ochreous yellow with the markings distinctly marked in black. The hindwings beneath has a large black spot in the anal fold which separates it from all other species.

Males are exceedingly fast flyers but often stop to perch with its forewings held at an angle with the hindwings opened flat in the typical Hesperiidae fashion.

A male Yellow Palm Dart perches in the usual skipper fashion

The caterpillar host plant on which the species was bred in Singapore is the Coconut Palm. However, the species is known to also feed on various other Palmae in Australia.

So, as we wish "G'day, mate" to this Australian "foreign talent" and new addition to the Singapore (and Malaysian) checklists - the Yellow Palm Dart, we also hope to one day see another similar Australian species the Orange Palm Dart (Cephrenes augiades) reaching the shores of Singapore.

Specimens shots of the Yellow Palm Dart, courtesy of the James Cook University, Australia

In conclusion, Kelvyn, if you are reading this article, you can now assure your skeptics that you indeed saw a Yellow Palm Dart here in Singapore in 1999. Your valued discussions over emails and articles and photos that you sent me are very much appreciated.

Text by Khew SK ; Photos by Sunny Chir, LC Goh, Khew SK & Horace Tan

Further Reading :

18 January 2010

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

16 January 2010

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.

  • 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