THE BUTTERFLY: April 2008

Life History of Arhopala athada athada

Life History of the Vinous Oakblue (Arhopala athada athada )

Butterfly Biodata:
Genus: Arhopala Biosduval, 1832
Species: athada Staudinger, 1889
Subspecies: athada Staudinger, 1889
Wingspan of Adult Butterfly: 48mm
Caterpillar Host Plants: Syzygium glaucum.

Physical Description of Adult Butterfly:
Being in the same cleander group of Arhopala genus, the adults of Vinous Oakblue are rather similar in appearance to the adults of Sylhet Oakblue (Arhopala silhetensis adorea) which was featured in an earlier blog article. The main difference between Sylhet Oakblue and Vinous Oakblue is found in the hindwing underside. For Vinous Oakblue, the post-discal spot in space 6 is rather quadrate and is as wide as the interval between the spot in space 5 and the end-cell bar, which it usually overlaps slightly.

An illustration of the differences between A. athada and A. silheltensis.
A: post-discal spot in space 7; B: post-discal spot in space 6;
C: end-cell bar; D: post-discal spot in space 5.

Field Observations of Butterfly Behaviour:
Though not very common in Singapore, this species has been encountered quite regularly both in urban parks and the Central Catchment Area. Usually they are sighted in the vicinity of their host plants. Typically they perch with its wings closed, but in sunny weather, the adults can be seen to open their wings fully to sunbathe.

Early Stages:
The similarity in appearance of adults between Vinous Oakblue and Sylhet Oakblue is also echoed in their life histories. Both have Syzygium spp. as their host plants, and their eggs, caterpillars and pupae have very similar shapes and markings. Visual differences are mainly in colorations and some markings.

Host plant for Vinous Oakblue: Syzygium glaucum.

Leaf venation pattern of a rather young leaf. Can you spot one tiny egg?

The egg is laid singly on the underside of a mature leaf. Each egg is about 0.7mm in diameter, white in color, circular with a slightly depressed micropylar area and a finely reticulated pattern of intersecting ridges.

Egg of the Vinous Oakblue

It takes 3 days for the collected egg to hatch. The newly hatched has a length of about 1.5mm 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 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 dashed dorsal line, reddish brown in color, appears. A large part of the first thoracic segment also changes from light brown to dark reddish brown.

1st instar caterpillar, newly hatched, length: 1.5mm

The 1st instar caterpillar feeds by skimming the surface of a young leaf. After 4 days of growth, and reaching a length of about 2.2mm, it moults to the next instar. The 2nd instar caterpillar has long fine lateral hairs, and a more distinct marking on the anal plate. There are also small reddish brown markings flanking the spiracles.

2nd instar caterpillar, length: 3.5mm

The 2nd instar caterpillar reaches a length of about 4mm, and after about 6 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 continuous reddish brown dorsal band, flanked by fluorescent yellow bands on both sides, running from the 2nd thoracic segment up to the anal plate and 3) the dorsal organ 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 7 days to complete with the body length reaching about 8mm.

3rd instar caterpillar, length: 4mm

The 4th instar caterpillar has similar markings as the 3rd instar. One notable change is in the dark marking on the first thoracic segment becoming smaller in proportion and better defined in shape. Another notable change is the loss of reddish brown markings flanking the spiracles. The 4th instar takes about 10 days to complete with the body length reaching 13mm.

4th instar caterpillar, 12mm

The 5th instar caterpillar has similar but more striking markings. Visible changes are 1) a white intermittent line running down the middle of the dorsal band and the well-shaped patches on the first thoracic segment and the anal plate; 2) the base body color becomes light yellowish with the first thoracic segment marked by a black edge; 3) each tentacular organ is highlighted in a black ring which is also connected to the main dorsal band.
After 12 days of feeding and reaching a length of about 25mm, 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.

5th instar caterpillar , length: 23mm

A pre-pupa of the Vinous 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. After 1 day 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 light brown in coloration.

Two views of a pupa, 16mm

Eight days later, the pupa matures enough to show the markings on the forewing upperside. The next day, the pupal stage comes to an end with the emergence of the adult butterfly.

A mature pupa (male)

A newly eclosed male

A newly eclosed female

In the wild, the caterpillars of the Vinous Oakblue have been found to be attended by Polyrhachis ants of the tibialis group as shown below.

A 5th instar caterpillar being attended by a Polyrhachis ant of the tibialis group

Acknowledgments:

I would like to express my gratitude to Prof. Konrad Fiedler, Dr Rudy Kohout and Dr. Pfeiffer for their generous assistance in confirming that Vinous Oakblue (Arhopala athada athada) is the species for which the life history is described above, and for providing the ID for the attending ant.

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

The Swallowtails of Singapore

The Swallowtails of Singapore

The Swallowtails generically refer to the family Papilionidae, which includes large butterflies and some of the most magnificent and majestic butterflies in the tropics. Although usually referred to as the "Swallowtails", many of the Malaysian and Singaporean species are tailless.

This article features the Papilionidae which are true "swallowtails" in that these species possess spatulate tails on the hindwings. All the five species of Swallowtails found in Singapore are large butterflies, predominantly black and prominently marked with white, red and blue.

The Swallowtail species are strong on the wing, except when feeding or ovipositing, and can take to the wing very ably if disturbed. A peculiarity of the flight of the Swallowtails is that the forewings flutter rapidly whilst the hindwings are kept fairly still - usually when feeding.

The host plants of the Swallowtails include several species of Rutaceae (e.g. Citrus, Murraya, Zanthocylum and Luvunga) and Aristolochiacea (A. acuminata, A. ringens and A. foveolata). Of the five species of Swallowtails found in Singapore, one belongs to the genus Pachliopta and the other four belong to the genus Papilio. All the species have jet black opaque eyes and robust clubbed antennae.

The five Swallowtail species found in Singapore are :

Common Mormon (Papilio polytes romulus)
Blue Helen (Papilio prexaspes prexaspes)
Great Helen (Papilio iswara iswara)
Banded Swallowtail (Papilio demolion demolion)
Common Rose (Pachliopta aristolochiae asteris)

The Common Mormon (Papilio polytes romulus)

The Common Mormon is probably the most abundant of the Swallowtails and is both an urban and a forest butterfly in Singapore. In urban areas, where its preferred host plant, Indian Curry Leaf (Murraya koenigii) is cultivated, the species is often seen ovipositing on the pungent leaves of the host plant. In forested areas, the caterpillars are usually found on the jungle relative of the Murraya. When the preferred host plant is not available, the caterpillars are sometimes found on various species of Citrus as well - most commonly on the Pomelo.

The male Common Mormon is predominantly black with a series of pale white spots running along the hindwing forming a band, with a few small spots along the margin of the forewings, creating a continuation of the hindwing band. On the hindwing, the underside has a series of red submarginal lunules.

The female is polymorphic in Malaysia and Singapore, with the form-cyrus resembling the male but has a red tornal spot in space 1a on the upperside of the hindwing. The female form-polytes resembles the Common Rose (Pachliopta aristolochiae asteris) but her black abdomen (as opposed to the Common Rose's red abdomen) instantly gives her away.

The Blue Helen (Papilio prexaspes prexaspes)

The Blue Helen is essentially a forest butterfly and is rarely seen in urban areas, preferring the sanctuary of Singapore's nature reserves. It is the rarest of the Swallowtail species in Singapore, and most often observed puddling along muddy footpaths in the nature reserves. Also a predominantly black butterfly, the Blue Helen has a white discal patch on the hindwings formed by large white spots. The underside hindwing feature a series of bluish grey spots towards the tornal area.

The species is swift on the wing and erratic in flight. The wings are more robust than the Common Mormon, and the spatulate tails are large and thick. Females are sometimes seen visiting flowers in the forested areas.

The Great Helen (Papilio iswara iswara)

The Great Helen is the largest amongst the Swallowtails found in Singapore. With a wingspan often exceeding 160mm, it is a spectacular butterfly when seen in flight. Like its closely related cousin, the Blue Helen, the Great Helen is also a forest butterfly, and remains mainly in the nature reserves, flying high amongst the treetops visiting the flowers of the trees like the Saraca and Syzygium spp. Occasionally, it descends to feed on low garden flowering bushes like the Ixora which are planted at reservoir parks fringing the nature reserves.

The large white patch on the hindwings extends from vein 4 to the apex and on the underside, there are blue lunules with large black-centred red ocellus at the tornal area. In the female, there is a pair of black-centred ocelli on the upperside of the hindwings at spaces 1a and 2.

When the Great Helen stops to rest, the forewings cover the most of the white patches on the hindwings, appearing totally black. It rests with wings opened flat on large leaves. When disturbed, it takes flight and there is a flash of white as the patches on the hindwings are revealed. It is believed that the momentary distraction of the white patches would surprise a predator for a split second, whilst the butterfly makes a hasty escape.

In Singapore, the Great Helen does not appear to puddle at damp streams like its cousins the Red Helen (Papilio helenus helenus) - found in Malaysia, and the Blue Helen.

The Banded Swallowtail (Papilio demolion demolion)

The Banded Swallowtail is another swift flying Swallowtail, often seen flying erratically amongst the forested areas in Singapore's nature reserves. Although sometimes seen in suburban gardens, the species still prefers to remain close to the sanctuary of the forested areas. The wings are black with a pale greenish macular band extending from the apex of the forewing to the mid-dorsum of the hindwing. The hindwing has a series of pale greenish lunulate submarginal spots and a black ocellus ringed with orange red at the tornus.

The spatulate tails are narrower and longer than the other Swallowtail species found in Singapore. The underside markings are paler and there is a series of attractive patterns on the hindwings with orange spots at the tornal and costal area.

The early stages of this species are unique in the sense that it is one of the very few species of butterflies which lays its eggs on top of each other, forming a rod protruding from a leaf of the host plant. The caterpillars are gregarious and feed together in the first four instars.

The Common Rose (Pachliopta aristolochiae asteris)

The Common Rose is a pretty Swallowtail, with its reddish pink spots and abdomen. The predominantly black forewings are shaded with grey along the distal half. The underside has a white post-discal patch and the series of reddish pink submarginal spots. The sexes are similar except for the rounder wing contours of the female.

The caterpillars of the Common Rose feeds on a variety of Aristolochia and it has been successfully bred on A. acuminata, A. ringens and A. foveolata. It is believed that it also feeds on Thottea sp as well.

The bright colours of the species is a warning to predators that it is distasteful. The female of the related Common Mormon (form-polytes) mimics the Common Rose for protection. In Singapore, the species can most often be found at the Singapore Botanic Gardens, Alexandra Hospital Butterfly Trail and the Singapore Zoological Gardens at Mandai, where its host plants are found.

Recently, the presence of what is believed to be a different subspecies of the Common Rose has been observed with regularity. This subspecies has totally black hindwings where the typical white patch of the subspecies asteris is missing. It is believed that this is the subspecies antiphus which is of Bornean origin. How this subspecies appeared in Singapore is a mystery. It could be that it was inadvertently imported with some plants or perhaps a gravid female accidentally escaped from the butterfly park at Sentosa and established a colony here in Singapore. No one can be certain of how it came to Singapore, but it is now quite regularly observed in Singapore.

There is a sixth "Swallowtail" which may occur in Singapore and this is the female form-distantianus of the Great Mormon (Papilio memnon agenor). The shot shown here, courtesy of Leslie Day of ButterflyCircle, was taken at Koh Samui in Thailand. This form of the female can also be found in Malaysia, and hence it should be looked for in Singapore. Though the predominant female forms in Singapore are form-esperi, form-butlerianus and form-agenor, this Swallowtail female form-distantianus has thus far not been reliably sighted nor photographed yet.

Text by Khew SK : Photos by Khew SK, Sunny Chir, Tan CP, Federick Ho, James Chia and Leslie Day

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