Life History of the Centaur Oakblue

Life History of the Centaur Oakblue (Arhopala centaurus nakula)

Butterfly Biodata:
Genus: Arhopala Biosduval, 1832
Species: centaurus Fabricius, 1775
Subspecies: nakula C & R Felder, 1860
Wingspan of Adult Butterfly: 48mm
Caterpillar Host Plants: Terminalia catappa (Combretaceae, Common name: Sea Almond), Syzygium grande (Myrtaceae); Syzygium aqueum (Myrtaceae); Macrosolen cochinchinensis (Loranthaceae), Hopea odorata (Dipterocarpaceae).


A Centaur Oakblue on a leaf perch


Another Centaur Oakblue on a leaf perch

Physical Description of Adult Butterfly:
This species is one of the largest within the Arhopala genus. Both sexes have more pointed forewing apex than usual. Hindwing cell is short, being less than half the wing length. A stout white-tipped tail is present at the end of vein 2 on the hindwing. Above, the male is purplish blue with a very narrow, thread-like dark border on the forewing while the female is paler purplish blue with broader black borders. Underneath, both sexes are brown with markings in darker brown and outlined with lines in paler brown. A purplish sheen can be observed on fresh specimens. A feature which immediately distinguishes this species from other Arhopala spp. locally is the presence of green silvery lines outlining spots in the forewing cell (refer to the area highlighted by a flashing red border in the picture below). The post-discal band on the forewing is continuous and a spot is present in space 10.

Another Centaur Oakblue to take off from a cement surface of a park bench.


A Centaur Oakblue perching on a branch.

Field Observations of Butterfly Behaviour:
This species is not uncommon in Singapore. Adults have been sighted in multiple habitats both in and out of the nature reserves, at places such as neighborhood gardens, hill parks, mangrove areas and off-shore islands. Usually they are sighted perching on leaves in the vicinity of their host plants, but the adults have also been observed to visit flowers (see the blog article at this link for related information on this behavior).

A Centaur Oakblue taking nectar from a palm inflorescence.


A close-up view of the eye of a Centaur Oakblue.

Early Stages:
The Centaur Oakblue is polyphagous as its early stages feed on a number of host plants from different families, including one parasitic plant, Macrosolen cochinchinensis. The caterpillars feed on the young to middle-aged leaves of the hosts, and typically build shallow shelters on the leaf. Between feeds, and when threatened, the caterpillars retreat to these shelters. The caterpillars also have a symbiotic relationship with ants, in particular the 'Weaver Ant' or Kerengga (Oecophylla smaragdina).

Host plant: Sea Almond. Leaves and fruits are featured here.

Host plant : Macroseolen cochinchinensis

The eggs are laid singly and sometimes in small groups on young shoots of the host plant. Each egg is about 1.0-1.1mm in diameter, white in color with a greenish tinge when freshly laid. It is circular with a depressed micropylar at the pole, a finely reticulated pattern of intersecting ridges on the surface, and pointed spines at intersections of these ridges.

Two views of an egg of the Centaur Oakblue
It takes 2.5-3 days for the egg to hatch. The newly hatched has a length of about 1.8-1.9mm and has a yellowish green coloration. It has a rather flattened woodlouse appearance with a large semicircular pro-thorax and a pale orangy head. This appearance remains in later instars. The body also carries long dorso-lateral and lateral setae (hair). A dark reddish marking can be seen on the dorsum of the 7th abdominal segment. As it grows, the body color becomes more yellowish and a dorsal band reddish in color appears on the last few abdominal segments.
A time-lapse sequence of the hatching event of a Centaur Oakblue caterpillar.

1st instar caterpillar, newly hatched, length: 1.9mm

1st instar caterpillars, length: 2.3m (top), 3mm (bottom).

After 1.5-2 days of growth in the first instar, and reaching a length of about 3mm, the caterpillar moults to the next instar. The 2nd instar caterpillar has long fine lateral setae and numerous very short and fine hairs all over the body surface. It is mostly yellowish green except for the reddish band on the dorsum on the last half of the abdominal segments. Even at this early stage, the dorsal nectary organ and tentacular organs are discernible on the 7th and 8th abdominal segments respectively.
2nd instar caterpillar, length: 3.3mm (top), 4.5mm (bottom).
Top: 2nd instar caterpillar, late in this stage, prior to its moult.
Bottom: 3rd instar caterpillar, newly moulted, length: 5mm

The 2nd instar caterpillar reaches a length of about 5.5mm, and after about 2 days in this stage, it moults again. The 3rd instar caterpillar is prominently marked with a rather broad dorsal band, reddish brown at the posterior segments but becoming more greenish and diffused as it extends and tapering toward the prothorax. From the 2nd thoracic segment to the 6th abdominal segment, the dorsal band is highlighted by a series of convex and dark line segments. The 3rd instar takes about 2-2.5 days to complete with the body length reaching about 9.5mm.
Two views of a 3rd instar caterpillar, length: 7.5mm
Top: a late 3rd instar caterpillar moments before its moult, length:9mm
Bottom: the same caterpillar soon after its moult to the 4 instar, length: 10mm.

The 4th instar ushers in further "enhancements" to the dorsal band. Now the band is made more prominent by narrow white areas appearing on the inner side of the dark outlines. From the 1st to the 6th abdominal segment, these convex dark lines also have a large lateral brown patch on each side. The patches become larger as the caterpillars grows in this instar. The dorsal band on the 6th abdominal segment is much narrower, allowing for a greater extent of body base colour between the band and the dark outlines. The dorsal nectary organ on the 7th abdominal segment is clearly marked and is flanked by narrow protruding brown markings. On the prothorax, a U-shaped brown marking nearly encircles the tapering end of the dorsal band. The spiracles are dark brown in color, standing out against the yellowish green base color of the body. Towards the end of this instar, the spiracles become encircled in orangy brown rings.The 4th instar takes about 2.5-3 days to complete with the body length reaching 20mm.
Two views of a 4th instar caterpillar, length: 13.5mm
Two views of a 4th instar caterpillar, length: 16.5mm


Two 4th instar caterpillars being attended by weaver ants in the field.

The 5th instar caterpillar has similar but more striking markings. Visible changes are 1) dark patches appear within the dark outlines of the dorsal band, thus leading to the appearance of an inner dorsal band; 2) each tentacular organ is highlighted in a black ring which is also connected to the main dorsal band; 3) lateral dark patches reaches all the way to the spiracles and nearly fill up the space between spiracles.
Two views of a 5th instar caterpillar, early in this stage, length:: 20.5mm


Close-up view of the body markings near the spiracles.


Close-up views of the posterior end of a 5th instar caterpillar, showing the location of the dorsal nectary organ (DNO) and tentacular organs (TO).After 5-6 days of feeding and reaching a length of about 31-32mm, the caterpillar slows down and actually stops food intake for about 1 day. During this time, its body length gradually shortened. Soon it becomes an immobile pre-pupa in its shallow leaf shelter.


Weaver ants attending to a 5th instar caterpillar.


Two views of 5th instar caterpillar, late in this stage, length: 30mm. Note the large droplet of nectary fluid exuded by the dorsal nectary organ.

The pre-pupa caterpillar prepares for pupation by spinning a silk girdle and a silk pad to which it attaches itself via cremastral hooks. After 1 day as a pre-pupa, pupation takes place. The predominantly brown pupa, with a length of 19-20mm, has a shape typical of any Lycaenid species, but with a somewhat produced anal segment.
Two views of a pre-pupa of the Centaur Oakblue lying (immobile) within its pupation shelter.


Two views of a pupa of the Centaur Oakblue.Even at the pupal stage, at least for the initial few days of this stage, a little slit on the dorsum of the 7th abdominal segment has been found to exude fluid droplets. This is likely the remnant or continuation of the dorsal nectary organ of the larval stage. It is no surprise that ants have been seen actively attending to the pupa during field observations. Thus the symbiotic relationship between the two species continues into the larval stage of the Centaur Oakblue.


A pupa of the Centaur Oakblue being attended by weaver ants.
Close-up views of the posterior end of a pupa, showing the remnant of the dorsal nectary organ still exuding fluid.

Nine to ten days later, the pupa turns rather dark, first in the wing pad and thorax, then progressively in the abdomen. The extent of the blue patches in the wing pads gives an early indication of the gender of the soon-to-emerge adult. The next day, the pupal stage comes to an end with the emergence of the adult butterfly.


Two views of a mature pupa of the Centaur Oakblue.


A newly eclosed Centaur Oakblue.

References:

• The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, The Malayan Nature Society.
• Butterflies of Thailand, Pisuth Ek-Amnuay, 1st Edition, 2006

Text by Horace Tan, Photos by Anthony Wong, Federick Ho, Ben Jin Tan, Khew SK and Horace Tan

Singapore Welcomes the Malay Dartlet

Singapore Welcomes the Malay Dartlet
Species #297 of the Singapore Checklist

It started with an innocuous request for an ID of a skipper that NParks Senior Biodiversity Officer Serene Chng of the National Biodiversity Centre (NBC) of NParks emailed to me. Her colleague, Jun-Yan's shot of a rather pristine specimen of this skipper, did not match the any pictures of the extant butterfly species in the Field Guide to the Butterflies of Singapore.

The dark brown underside, coupled with a sharply defined orange-yellow discal band on the underside of the hindwing indicates that this is a Malay Dartlet (Oriens paragola). Upon looking at various reference books, it was concluded beyond doubt that this species is indeed the Malay Dartlet, which was not recorded in the Singapore Checklist by the early authors.

Although described as a species that frequents lowland forest in Malaysia, it was either missed out by the early authors or the species may have migrated over to Singapore over the years. ButterflyCircle member, Sunny Chir, made a trip to check out the area where this skipper was photographed, and was rewarded with a sighting and a shot of another specimen of the Malay Dartlet in the same vicinity where the first one was shot. Subsequent checks at the location where the species was first photographed indicated that there was already a small colony of the species there, and more individuals were observed amongst the grassy patches, together with other Hesperiidae.

A comparison of Jun-Yan's shot with a typical Common Dartlet shot

With Jun-Yan's latest shot of a pristine specimen in a nature reserve, Species #297, the Malay Dartlet, which is new to Singapore, is added to the Checklist. The genus Oriens is now represented by two species in Singapore's butterfly fauna.

The Malay Dartlet differs from the more often encountered Singapore species, the Common Dartlet (Oriens gola pseudolus) in having undersides that are dark brown, with a distinct orange-yellow discal patch on the hindwing and other markings reflecting the upperside markings. The contrasting orange-yellow markings are distinctive and a diagnostic feature that distinguishes this species from other similar lookalike species. The orange markings are also not edged with black spots, unlike the two other related species in the genus.

ButterflyCircle credits the discovery of the Malay Dartlet in Singapore to Sek Jun-Yan, Senior Biodiversity Officer of the National Parks Board, whose fortunate encounter with this species confirms a new addition to the Singapore butterfly fauna.

Text by Khew SK : Photos by Sek Jun-Yan, Sunny Chir and Khew SK

The Return of the Admiral

The Return of the Admiral

The Indian Red Admiral calls at the port of Singapore again

A pristine Indian Red Admiral visits Singapore again in 2011!

Some time back in Dec 2008, the Indian Red Admiral (Vanessa indica) was spotted at an urban park in Singapore (see previous blog article). Back then, it was the first time anyone had spotted this species as far south as Singapore. It may have been a once-off occurrence, where a migrating individual could have have been blown off course by the strong North-East monsoons and it ended up taking refuge in Singapore.

Indian Red Admiral shot in Dec 2008

Then recently, on 8 Jan 2011, ButterflyCircle's eagle-eyed Sunny Chir again spotted this species puddling at the same urban park! Most amazingly, it was flying around in the exactly the same vicinity as the individual spotted over two years ago!

Indian Red Admiral shot on 8 Jan 2011

Is there some DNA imprinted code that makes this particular species come back again and again to the same location in Singapore? Was it part of a fixed migratory route or just pure coincidence? Did it return in 2009 and 2010, but just that no one spotted it? This particular individual came rather early in the year, or perhaps it was one of several of the same species that remained since the latter part of 2010.

Indian Red Admiral shot in Dec 2008

One of those intriguing mysteries in nature. This visiting Indian Red Admiral shot in 2011 appears too pristine to have suffered the battering winds and wear and tear of a long migratory flight. Perhaps the species has already established a colony in Singapore, and breeding new offspring somewhere, as the host plant is known to be some species of nettle (family : Urticaceae)

Indian Red Admiral shot on 8 Jan 2011

Who knows for sure? We just need to be continuously observant, and with a good dose of luck, like Sunny Chir seems to have, and we may just get our answer!

Text by Khew SK : Photos by Sunny Chir & James Chia

Life History of the Yellow Banded Awl

Life History of the Yellow Banded Awl (Hasora schoenherr chuza)



Butterfly Biodata:
Genus: Hasora Moore, 1881
Species: schoenherr Latreille, 1824
Subspecies: chuza Hewitson, 1867
Wingspan of Adult Butterfly: 45mm
Caterpillar Local Host Plants: Two species to be identified.


A Yellow Banded Awl perching the broken end of a branch.


A Yellow Banded Awl perching on the underside of a palm frond.

Physical Description of Adult Butterfly:

Adults are rather large in size with pointed forewing apex and markedly lobate hindwings. Above, the wings are dark brown. For both sexes on the forewing, there are four whitish sub-apical spots, and three rather large yellowish hyaline spots, one each in the cell and in spaces 2 and 3. These hyaline spots are adjoined to form a broad but irregularly-outlined band. The male has a yellowish discal stigma. On the hindwing, there is a broad yellowish discal band and the wing borders are marked with yellowish cilia. Below, both sexes are similarly marked as per the upperside but with wing bases in paler brown, and that the apical to post-discal area of the forewing has a strong purplish sheen in some specimens.

A partial view of the upperside of a Yellow Banded Awl.


A side view of the same Yellow Banded Awl featured in the previous picture.

A Yellow Banded Awl found perching on the underside of a leaf after a shower.

Field Observations of Butterfly Behaviour:

This species is uncommon in Singapore. Sightings of the adults have so far been confined to a handful of locations within the Central Catchment Nature Reserve. Typical encounters involve an individual flying among foliage alongside walking trails or at forest fringes, and occasionally puddling individuals on damp patches of soil. As with other Awl spp., the fast flying adults have a habit of resting on the underside of a leaf or other plant parts.

A Yellow Banded Awl puddling on a damp ground.


A Yellow Banded Awl checking out the surface of a leaf with its proboscis.

A Yellow Banded Awl perching on a tree trunk in the nature reserve.

Early Stages:

Two vines growing in the Catchment Reserve have been recorded as the local host plants. The first is tri-foliated with smooth leaf surface while the second is 5-foliated with leaf surface covered with dense short hair. Their exact species ID are yet to be established. Igarashi and Fukuda, in their voluminous book on life histories of Asian butterflies, mentioned Fordia ngii (Malay Peninsula) and Spatholobus palawanensis (Palwans) as host plants of the Yellow Banded Awl. It is likely that the two local host plants also belong to the same genera (within Leguminosae). Caterpillars of the Yellow Banded Awl feed on the very young to the moderately young (before hardening) leaves of the host plants.

Host plant #1; a vine with tri-foliated leaves, with smooth leaf surface.


Host plant #2: a vine with 5-foliated leaves, with "rough" leaf surface.

The eggs are laid singly on very young shoots of the host plants. Each egg is shaped like a bun with a flattened base (diameter: 0.8-0.9mm). Prominent ridges run from the pole to the base. The micropylar sits atop at the pole. The entire egg turns salmon red as it develops, and then decolorizes again when the caterpillar is ready to emerge.

Two views of an egg of the Yellow Banded Awl, likely be one-day old.


Two views of a mature egg of the Yellow Banded Awl.

Two views of an empty egg shell of the Yellow Banded Awl.

It takes 2 days for the collected egg to hatch. The young caterpillar eats just enough of the shell to emerge, and has a length of about 2mm. It has the typical cylindrical shape for skipper caterpillars, and the yellowish body has a number of short white setae and lateral orangy patches. The large head is black, slightly bi-lobed and lightly hairy. The dorsum of the prothorax carries a dark-colored patch/shield.

Two views of a 1st instar caterpillar, early in this stage, length: 2.3mm.


A newly hatched caterpillar checking out its surrounding on host plant #2.

The young caterpillar constructs its first leaf shelter by bringing two halves of a small young leaf together with silk threads. It rests within the flap and ventures out to eat on nearby leaf surface. In later instars, the Yellow Banded Awl caterpillars also construct leaf shelters in a similar fashion but do so with larger and older leaves. The larval growth of the Yellow Banded Awl is rapid in pace for all instars, with all but the final instar lasting only 1-1.5 days.

A field shot of a pinna of host plant #2 showing an empty eggshell and a 1st instar caterpillar in a leaf shelter.


Two views of a 1st instar caterpillar, late in this stage, dormant before its moult, length: 3.5mm.

After reaching a length of about 3.5mm in the 1st instar, the caterpillar moults to the next instar after a short dormant period. The 2nd instar caterpillar has four faint whitish narrow dorsal bands which are barely visible against the yellowish green ground color. There are lateral patches, brown initially but blacken gradually, one to each of all body segments except for the anterior two. The body and the black head capsule are covered in short fine setae. Toward the end of this instar, faint pale rings become visible on the body segments.

Two views of a 2nd instar caterpillar, early in this stage, length: 5mm.


A 2nd instar caterpillar, late L2. Top: length: 7mm. Bottom: dormant before the next moult.

The 2nd instar caterpillar reaches a length of about 7mm, and after 1.5-2 days in this stage, it moults again. The 3rd instar caterpillar resembles the 2nd instar caterpillar but with broader and more prominent dorsal yellowish bands and segmental yellowish rings, all set against a more greenish body colour. The lateral dark patches are now more prominent on meta-thoracic segment, abdominal segments 2,4,6,8-10 but those on other segments appear to fade away. This instar lasts another 2 days with the length reaching 11-12mm.

Two views of a 3rd instar caterpillar, newly moulted, length: 7.5mm.


Two views of a 3rd instar caterpillar, late in this stage, length: 14mm.

A 3rd instar caterpillar, dormant before the next moult, length: 13mm.

The 4th instar caterpillar resembles the 3rd instar caterpillar closely, but with dorsal bands and segmental rings much more constrasting, and the dark lateral patches better defined. The head capsule is still black for most 4th instar caterpillars, but some specimens have been observed to feature small lateral patches of red to reddish brown. This penultimate instar takes about 2 days to complete with the body length reaching up to 24mm.

Two views of a 4th instar caterpillar, newly moulted, length: 12mm.


Two views of a 4th instar caterpillar, length: 15.5mm.


Two views of a 4th instar caterpillar, length: 22mm.

A 4th instar caterpillar, dormant before the next moult, length: 24mm.

The final and 5th instar caterpillar has similar body markings as the 4th instar caterpillar. Noteworthy is that an additional pair of dark lateral patches, though small in size, appear on the meso-thorax. A much more striking change is in the head capsule which has now become reddish or orangy red. Set against this brightly coloured background are two lateral round black spots and one triangular black spot on the frons (about the labrum). White setae adorn the head capsule as well as the entire body. This stage takes about 4-5 days to complete with body length reaching up to 42mm.

Two views of a newly moulted 5th instar caterpillar, early in this stage, length: 23mm.


Two views of a 5th instar caterpillar, late in this stage, length: 42mm.

Towards the end of 5th instar, the body of the caterpillar gradually shrinks in length and decolorises, losing all its yellow luster in the process. The fully grown caterpillar ceases feeding and stations itself in a leaf shelter. During the early part of this pre-pupal stage, the caterpillar spins large quantity of silk threads to seal the pupation shelter, and in particular, constructs a silk girdle at its 2nd/3rd abdominal segment and a short transverse silk band near its posterior end. Both the dorsal point of the girdle and the transverse band are also secured by vertical/oblique threads to the inner wall of the shelter.

Two views of a 5th instar caterpillar, ceased feeding and shrunken, length:30mm.

Two views of a pre-pupa of the Yellow Banded Awl secured in its pupal shelter. Note the dorsal girdle and posterior transverse band.

After about 0.75 day of the pre-pupal phase, pupation takes place within the pupation shelter. The pupa secures itself with its cremaster attached to the transverse band. The pupa has a short thorax, a rather long abdomen and a short and pointed black rostrum. Fresh after the pupation event, the body is pale whitish with a light greenish undertone, but after 0.5 to 1 day, the body surface becomes mostly covered in a white substance. Several black spots adorn the dorsum of the thoracic segments. The spiracles are marked in black. Length of pupae: 22-23mm.

Two views of a pupa of the Yellow Banded Awl, early in this stage, still without the coating of whitish powdery substance.


Two views of a pupa of the Yellow Banded Awl, day 2 in this stage, now with the coating of whitish powdery substance.

After 8 days, 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 Yellow Banded Awl


A newly eclosed male Yellow Banded Awl still awaiting its wings to be fully stiffen up.

References:

• The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, The Malayan Nature Society.
• Butterflies of Thailand, Pisuth Ek-Amnuay, 1st Edition, 2006
• The Life Histories of Asian Butterflies Vol.2, Igarashi S. & Fukuda H., Tokyo University Press, 2000.

Text by Horace Tan, Photos by Nelson Ong, Sunny Chir and Horace Tan