Life History of Arhopala silhetensis adorea

Life History of the Sylhet Oakblue (Arhopala silhetensis adorea)

Butterfly Biodata:
Genus: Arhopala Biosduval, 1832
Species: silhetensis Hewitson, 1862
Subspecies: adorea de Niceville, 1890
Wingspan of Adult Butterfly: 48mm
Caterpillar Host Plants: To be identified.

Physical Description of Adult Butterfly:
The adult is moderately large and has a pair of white-tipped tails at the end of vein 2 on the hindwing, where tornal lobes are also present. As with other members of the cleander group of Arhopala, the post-discal band on the hindwing underside is dislocated at vein 2 with spots in spaces 6 and 7 placed one below the other. For A. silhetensis, the outer edge of the spot in space 7 is well inside the outer edge of the spot in space 6; the latter wider at top than at bottom, with its outer edge sinuous and inside the inner edge of the spot in space 5, and its inner edge not overlapping the end-cell bar. Further, the gap between the spot in space 5 and the end-cell bar are wider than either of these spots. On the upperside, the adult is deep purple blue with narrow borders in the male, and shining purplish blue with broad borders in the female.


An adult with key features of hindwing underside indicated

Field Observations of Butterfly Behaviour:
This species is currently considered rare in Singapore. It is only recently rediscovered in a localized area within the Central Catchment Area. The adults were spotted flying next to the forest trails and at times perching with its wings closed. In sunny weather, some were also observed to fully opening its wings to sunbath on its perch.


An encounter with an oviposting female in October 2007.

Early Stages:

Host plant: to be identified.


Host plant: leaf venation pattern of a rather young leaf.

Eggs are laid singly on the underside of an old leaf. The egg shares a similar appearance with a number of Arhopala species. Each egg is small, about 0.5mm in diameter, and white in color, circular with a slightly depressed micropylar area and a finely reticulated pattern of intersecting ridges.


Egg of the Sylhet Oakblue


Empty egg shell

It takes 3 days for the egg to hatch. The young caterpillar eats only the upper portion of the egg shell to emerge. The newly hatched has a length of about 2mm and has a light brown coloration. It has a rather flattened woodlouse appearance with a large semicircular first thoracic segment. This appearance remains as the caterpillar grows through the instars. A large dark brownish marking can be seen on the anal plate. The body also carries long dorsal and lateral hairs. As it grows, the body color becomes more yellowish and a faint white dorsal line appears.


1st instar caterpillar, newly hatched, length: 2mm


1st instar caterpillar, 2.5mm

The 1st instar caterpillar feeds by skimming the surface of a young leaf. After 4 days of growth, and reaching a length of about 3.5mm, it moults to the next instar. The 2nd instar caterpillar has long fine lateral hairs, and a more distinct marking on the anal plate. A pair of reddisk brown markings also sits on the first thoracic segment. The feeding is still done via eating away the upper layer of the young leaf. Nectary organs, including both the dorsal and tentacular organs are now discernible.


2nd instar caterpillar, early in this stage, length: 3.5mm

The 2nd instar caterpillar reaches a length of about 6mm, and after about 4 days in this stage, it moults again. The 3rd instar caterpillar is prominently marked with 1) a large dark patch on the 1st thoracic segment; 2) a wide reddish brown dorsal band running from the 2nd thoracic segment up to the anal plate, with a thin white band sitting within it; and 3) the dorsal organ now is lined with dark "lips" and sits within an oval marking. The caterpillar now feeds by eating along the leaf edge and devours the whole leaf. The 3rd instar takes about 4 days to complete with the body length reaching about 9mm.


3rd instar caterpillar, length: 8.5mm

The 4th instar caterpillar has similar markings as the 3rd instar. All markings have become darker in coloration, and the dark patches on 1st thoracic and the anal plate have also become larger and hence more prominent. The 4th instar takes about 4 days to complete with the body length reaching 16-17mm.


4th instar caterpillar.

The 5th instar caterpillar has similar but more striking markings. Visible changes are 1) all bands and patches are bolder and darker; 2) the lateral edge of the body is marked with a thin black line; and 3) each tentacular organ is highlighted in a black ring which is also connected to the main dorsal band. This last feature on the tentacular organs is also seen in caterpillars for Central Oakblue and the Flos species.After 8 days of frantic feeding and reaching a length of about 27mm, the caterpillar slows down and actually stops food intake for about 3 days. During this time, its body length gradually shortened. Soon it becomes an immobile pre-pupa in its shallow leaf shelter.


5th instar caterpillar, early in this stage, length: 18mm


5th instar caterpillar, late in this stage, length: 27mm


Two views of a pre-pupa of the Sylhet Oakblue

The pre-pupa caterpillar prepares for pupation by spinning a silk girdle and a silk pad to which it attaches itself via cremastral hooks. Also 2 days as a pre-pupa, pupation takes place. The pupa, with a length of 15-16mm, has a shape typical of any lycaenid species, but with a somewhat produced anal segment. It is initially jade greenish but within hours it becomes deep dark brown.


Two views of a pupa, 15-16mm

Ten days later, the pupal stage comes to an end with the emergence of the adult butterfly.


A newly eclosed female


A newly eclosed male

In the wild, the caterpillars of the Sylhet Oakblue have been found to be attended by the rather large ants of the species Polyrhachis armata, as the pictures below show.


A 5th instar caterpillar being attended by Polyrhachis armata ants


A 3rd instar caterpillar attended by a Polyrhachis armata ant

Acknowledgments:

I would like to express my gratitude to Prof. Konrad Fiedler, Mr. Les Day, Dr Rudy Kohout and Dr. Pfeiffer for their generous assistance in the identification of the Sylhet Oakblue (Arhopala silhetensis adorea) and the ant Polyrhachis armata.

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 and Photos by Horace Tan

ButterflyCircle re-discovers the Sylhet Oakblue

ButterflyCircle re-discovers the Sylhet Oakblue (Arhopala silhetensis adorea)

The genus Arhopala is one of the most challenging to identify and distinguish the look-alike species in the group, and definitely not easy to identify from field shots. However, ButterflyCircle is pleased to announce the re-discovery of the Sylhet Oakblue (Arhopala silhetensis adorea) and added it as species #282 in the Singapore Butterfly Checklist.

It started when ButterflyCircle member Sunny Chir spotted a medium-sized Arhopala fluttering amongst some low bushes in the shady forest along a jungle trail in the Central Catchment Area. Having earlier spotted the Green Oakblue in the same location, he thought that it was the female of the Green Oakblue that he shot.

Another ButterflyCircle member, Horace Tan, who later went to the same location, was fortunate enough to spot a female of this species ovipositing on its host plant. Having been able to document the entire life history of this species earlier and comparing the early stages, it was found that this Arhopala was not the Green Oakblue (see Life History of Green Oakblue).

The search for the identity of this species then went overseas, and ButterflyCircle member Keith Wolfe of the USA referred us to Prof Konrad Fiedler, a German expert in the Lycaenidae family of butterflies for help. Another ButterflyCircle member, Leslie Day, a resident of Koh Samui in Thailand, also lent his experience and time to help us identify this unknown Arhopala.

Having studied and compared the life history of this Arhopala species, and the key physical characteristics of the adult butterflies that were bred, it is now confirmed that this species is the Sylhet Oakblue (Arhopala silhetensis adorea).

The full life history of this hitherto unrecorded species will be published shortly in this blog by Horace Tan.

Well done to Sunny and Horace for their sleuthing skills and patience in helping us re-discover this species which was recorded in the early authors' checklists of Butterflies of Singapore. We now have 282 species on our Little Red Dot, and more to come soon!

Text by Khew SK ; Photos by Horace Tan & Khew SK

Life History of the Dark Posy

Life History of the Dark Posy (Drupadia theda thesmia)

Following the earlier blog article on the Three Posies, Horace Tan shares his latest discovery on the life history of one of the Posies - the Dark Posy.

Butterfly Biodata:
Genus: Drupadia Moore, 1884
Species: theda C. & R. Felder, 1862
Subspecies: thesmia Hewitson, 1863
Wingspan of Adult Butterfly: 35mm
Caterpillar Host Plants: Combretum sundaicum

Physical Description of Adult Butterfly:
The typical form of the male is dull purple above, whereas the -f minara form has an orange discal patch on the forewing. The female is brown, with a bluish grey tornal patch on the hindwing which has a few black submarginal spots. On the underside, the forewing is orange brown in the male and orange in the female, and the hindwing is mainly white; the forewing is marked with darker transverse stripes, and the hindwing markings consist of black spots and lines, with metallic green scalings and black spots at the tornus. There are three pairs of tails at the end of veins 1b, 2 and 3 on the hindwing. The species can be distinguished from the rather similar D. ravindra (Common Posy) in that the space between the two black stripes forming the cell-end bar on the underside hindwing is white, and not filled in with black as with D. ravindra.

Field Observations of Butterfly Behaviour:
This species is relatively rare in Singapore and it is mainly found at localised areas within the Central Catchment Area where the host plant Combretum sundaicum is common. In the early afternoon, the adult butterflies can be spotted flying from one perch to another perch in quick zig-zag flights. In sunny weather, they have the habit of fully opening their wings to sunbathe.

Early Stages:

Host plant : Combretum sundaicum


Host plant : Combretum sundaicum, young shoot

Eggs are laid singly on the young stem or the petiole of the liana (woody climber) Combretum sundaicum. Each egg is white with a beige tinge; circular with a depressed micropylar area and has many tiny pits dotting the surface. With a diameter of 0.9mm, the egg is rather large for a lycaenid species.


Egg of Dark Posy


Mature egg (top), empty egg shell (bottom)

It takes 2 days for the collected egg to hatch. The young caterpillar eats away the upper portion of the egg shell to emerge. With a length of about 2mm, it is cylindrical with long setae (hairs) and pale green in color. As it grows, it will assume the more typical onisciform (woodlouse) shape.


1st instar caterpillar, newly hatched, length: 2mm


1st instar caterpillar, 2.5mm

The 1st instar caterpillar feeds by skimming the surface of a young leaf. After 2 days of growth, and reaching a length of about 4mm, its moults to the next instar. The second instar caterpillar has short fine hairs covering its body and two stripes of faint white markings flanking the green dorsal ridge. The prothoracic shield is diamond in shape but rather inconspicuous. The feeding is still done via eating away the upper layer of the leaf surface.


2nd instar caterpillar, early in this stage, length: 5mm

The 2nd instar caterpillar reaches a length of about 7mm, and after 2 days in this stage, it moults again. In the 3rd instar, the dorsal markings are more prominent and the anal plate also features a fine red line. The caterpillar now feeds by eating along the leaf edge and devours the whole leaf. The typical lycaenid nectary organs (both dorsal organ and lateral tentacular organ) are now discernible. Even in the absence of ants, the dorsal organ excretes plentiful amount of clear fluid, suggesting a strong caterpillar-ant association in the wild. The 3rd instar takes 3 days to complete with the body length reaching about 10-11mm.


3rd instar caterpillar, length: 9.5mm


3rd instar caterpillar, length: 9mm, resting for the moult to next instar

The 4th (and final) instar caterpillar still has the same dorsal markings as in earlier instars, but the prothoracic shield has taken on two vertical rows of black, saw-toothed markings. New to the anal plate is a small oval-shaped area marked with a short black bar. The 4th instar takes about 4 days to complete with the body length reaching 20-21mm. Nearing the end of this instar, the caterpillar ceases feeding, and its body shrinks in length. Soon it comes to rest on the leaf surface and becomes an immobile pre-pupa.



4th instar caterpillar, early in this stage, length: 14mm


Pre-pupa of Dark Posy

The pre-pupa caterpillar prepares for pupation by spinning a silk girdle and a silk pad to which it attaches itself via cremastral hooks. Finally after 12 days of larval growth, pupation takes place. The pupa has a shape typical of any lycaenid species, and a length of about 14mm. It is light yellowish brown and dotted with small black specks.


Fresh pupa of Dark Posy

Seven days later, the pupa becomes darkened in color signaling the imminent emergence of the adult. The uppersides of the forewings become visible through the now transparent pupal skin, allowing one to tell the gender of the soon-to-appear adult. The next day the adult butterfly emerges from the mature pupa.


Mature pupa of Dark Posy (male)



A newly eclosed Dark Posy resting on young leaf of its host plant


Another Dark Posy in the field

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 Pres 1999

Text and Photos by Horace Tan

Butterfly of the Month - April 2008

BUTTERFLY OF THE MONTH - APRIL 2008
The Plane (Bindahara phocides phocides)

The Plane belongs to the genus Bindahara of which this species is the only representative in Singapore. It is very rare and local in distribution, found mainly in a small area at the forest edge of the Central Catchment Nature Reserves. Some prominent physical features of the Plane are the long hindwing tails (2 cm or longer) and pendulous tornal lobe on the hindwing.

The male of this species is a deep blackish brown above with the apical area of the forewing dusted brownish red. There is a narrow blue marginal line above vein 4 on the hindwing in some individuals. The female is reddish brown with a large black spot in space 2 of the whitened tornal area of the hindwing.

The undersides of the males are ochreous buff, with darker brown bands on the forewings, and spots on the hindwings. There are black tornal spots on the lobes and spaces 1b and 2 on the hindwing are overlaid with metallic green scaling. The long tails of the males are yellow.

Females feature whitish ground colour on the undersides, with similar marking as in the males, with the apical areas of the forewings a light orange-brown. The tails of the females are white. Both sexes have orange tipped antennae, and large jet black eyes. The adult butterfly has a wingspan of about 40mm.

The Plane can be observed in the late morning on sunny days, either feeding on the flowers of flowering trees like the Syzygium spp., and the forest bush Leea indica of which many of these photos feature, or just flitting amongst the tall leaves of bushes and trees in the nature reserves. In Singapore, males are more often encountered than females.

The Caterpillars of this species are basically white with areas of yellow and pink, but they have dark brown tubercles on each segment each bearing a black hair. The Caterpillars grow to a length of about 2 cms. They feed on the seeds within the fruit of Salacia chinensis and Salacia disepala. The Caterpillars bore into the bark of the tree to pupate. The pupa is brown and rough, with patches of white and dark brown. Its length is about 1 cm. When disturbed, the pupa emits clicking noises.

Text by Khew SK ; Photos by Khew SK & Federick Ho

References :

• Don Herbison-Evans & Stella Crossley : "Caterpillars of Australia" - Life History of Bindahara phocides yurgama

Life History of the Lime Butterfly

Life History of the Lime Butterfly (Papilio demoleus malayanus)

An updated version of the life history of the Lime Butterfly is available by clicking on this link.

Butterfly Biodata :

Genus : Papilio (Linnaeus, 1758)

Species : demoleus (Linnaeus, 1758)
Subspecies : malayanus (Wallace,1865)
Common name : Lime Butterfly
Wingspan of Adult Butterfly : 60 – 80mm
Caterpillar Host Plant : Citrus microcarpa

Physical Description of Adult Butterfly :

On the upperside, the wings of the Lime Butterfly are black with large yellow markings. These form an irregular macular fascia running from the apex of the forewing to the mid-dorsum on the hindwing, and there is a series of yellow submarginal spots on both wings. At the bottom of the hindwing (space 1b) is a red spot with an anterior narrow blue lunule. As for the female, this blue lunule forms the anterior portion of a large black circular spot above the red spot. The underside is predominantly yellow with a series of reddish post-discal bars on the hindwing.

Field Observations of Butterfly Behaviour :

This butterfly is common in gardens wherever the host plants of the species, Citrus spp. are cultivated. It is a strong flyer with a rapid erratic flight. It flies from flower to flower in search of nectar. Like many Papilionidae it has a characteristic flight when feeding, in that whilst the forewings are flapping rapidly, the hindwings are held almost stationary as if to balance the butterfly perched on a flower as it sucks nectar from the flower with its long proboscis.

In the cool morning hours, the Lime Butterfly may be found resting amongst shrubbery, sunbathing with its wings opened flat, as if to warm up before taking flight and going about the day's business.

An interesting phenomenon, particularly in the more affluent Asian countries, is that during the Lunar New Year celebrations, the Lime Butterfly appears to be more common than usual, due to the discarded Citrus plants which are traditionally purchased with the orange fruits ripened, to signify wealth during this Chinese festival. With the abundance of its host plant during this season, the female Lime Butterfly will waste no time ovipositing on the available host plants.

Early Stages :

The eggs are oviposited singly on the young leaves of the Citrus host plant. The egg is smooth, round and yellowish in colour, measuring around 1mm in diameter.

The egg of Lime Butterfly

After about 3-4 days, the caterpillar hatches from the egg, and immediately starts to consume the eggshell completely. The caterpillar then starts to eat the young leaf that the egg was laid upon.

The 1st instar caterpillar has a spiky appearance. The colour of its body is brown with yellowish-white markings with white hairs. As it feeds, the caterpillar usually stays in the middle of the upper side of the leaf. The first few instars of the caterpillar resemble bird droppings where it escapes predation by camouflaging itself in this manner.

1st instar Lime Butterfly caterpillar (3mm) consuming its eggshell upon hatching

As it moults into the 2nd instar, the dirty greenish-brown colour of its body remains similar as the 1st instar except that the saddle white band has widened somewhat. The hairy spikes of the 1st instar now take a more solid rubbery appearance.

2nd instar Lime Butterfly caterpillar (8mm)

In the 3rd instar is essentially similarly patterned as the 2nd instar. The colour of its body becomes richer, with white patches appearing near its head and last abdominal segments. It has an oily glossy appearance.

3rd instar Lime butterfly caterpillar (14mm)

In the 4th instar caterpillar, more whites patches appear throughout its body, dominating the earlier brown colour. The head also appears lighter in colour.

4th instar Lime butterfly caterpillar (25mm)

In the 5th or final instar, the caterpillar becomes a plain uniform green with a few dark brown markings. It has a pair of false "eyes" near its actual head, appearing much larger and fiercer to ward off predators. Also, when disturbed the caterpillar extrudes a pair of orange-yellow processes from the segment just behind the head, known as osmeterium, to alarm would-be predators.

Final instar Lime butterfly caterpillar (40mm)

After a total of 11 days upon hatching from the egg, the caterpillar then goes into a day of dormant pre-pupation pose after carefully selecting a perch onto which it can pupate upright.

Pre-pupa of the Lime butterfly

The pupa is light green with two projections to the front on its head and also one on its thorax. The abdominal segments are a bright lime green as opposed to the toned down green of the rest of the pupa. A silken girdle helps the pupa stay in an upward position.

Pupa of the Lime Butterfly (10x30mm)

After about 10 days, the pupa shell turns transparent and the wings of the butterfly can be seen through the semi-transparent pupa shell.

Upon eclosion, the adult butterfly emerges and hangs its wings out to dry, as it pumps fluids into the wings to expand them. When its wings are sufficiently dry and hardened, usually after about an hour or more, it takes its maiden flight.

Adult Lime Butterfly (underside view)

Adult Lime Butterfly (upperside view)

Text by LC Goh ; Edited by Khew SK ; Photos by LC Goh, Tan BJ and Neo CB.