Butterfly of the Month - May 2008

BUTTERFLY OF THE MONTH - MAY 2008
The Plain Nawab (Polyura hebe plautus)

The Plain Nawab (Polyura hebe plautus) belongs to the sub-family Charaxinae, which feature large, heavy-bodied robust butterflies which are capable of rapid and swift flight. There are seven known species of this genus in Malaysia, of which two are found in Singapore. Both species, the Plain Nawab (Polyura hebe plautus) and the Blue Nawab (Polyura schreiber tisamenus) are not considered very rare.

The Plain Nawab is the commoner of the two known species of the genus in Singapore. The butterfly is greenish white above and the forewing has a broad black apical border, which is very wide at the apex, but decreases in width towards the tornus and base of the costa. There is a greenish white subapical spot on the forewings and a series of submarginal spots on the hindwings.

The underside has a large, pale silvery green median patch, which covers a little more than a quarter of the wing. It is represented by the subspecies plautus in Singapore, and which can be distinguished by a broad black bordered hindwing. The Malaysian subspecies that is usually encountered, chersonesus, has a narrow hindwing border.

As in most of the typical Polyura species, the hindwings of the Plain Nawab feature a pair of short stubby tails each – slightly broader and longer in the female and narrower and sharper in the male.The butterfly has a strong and erratic flight. It has a habit of perching on a lofty leaf or branch, surveying the grounds below. It then flies rapidly in the vicinity of its perch, often 'attacking' intruders and chasing other flying objects away, but coming back again and again to the same preferred perch to rest. This species can also be observed puddling on roadside seepages, carrion, faeces and tree sap.

A Plain Nawab puddling at a sandy seepage.


A Plain Nawab feeding on tree sap

The caterpillar of the Plain Nawab feeds on the Leguminosae Adenanthera pavonina (commonly known as the Red Saga). Females of this species have also been observed ovipositing on the young Petai (Parkia speciosa) plant, and Albizzia (Falcataria moluccana) both of which appear to be an alternative host plants.

Its habit of weaving a silken pad on one of the leaves as its “base camp”, from which it makes it nocturnal forays to other parts of the Saga plant to eat, is a behaviour unique to both the Polyura species in Singapore. As the caterpillar grows larger, it takes on a two-shade green appearance, with triangular wedge-shaped stripes along the length of its body. It is interesting that it still maintains its silken pad base-camp, although the pad now consists of many leaves weaved together to accommodate the large caterpillar. It makes no attempt to conceal itself, and stays stationary on its silken pad in the daytime, feeding mostly at night.

Final instar caterpillar of the Plain Nawab resting on its "base camp". The host plant is Falcataria moluccana  in this case.

Another puddling Plain Nawab

Mating pair of the Plain Nawab

Text by Khew SK : Photos by Horace Tan, James Chia and Khew SK

Life History of White Spot Palmer

Life History of the White Spot Palmer (Eetion elia)

Butterfly Biodata:
Genus: Eetion de Nicéville, 189
Species: elia Hewitson, 1866
Wingspan of Adult Butterfly: 38mm
Caterpillar Local Host Plant: Sarcotheca griffithii (Oxalidaceae)

Physical Description of Adult Butterfly:
Above , the wings are dark brown with the forewing possessing separated white hyaline spots in the cell and in spaces 1b, 2, 3, 4 and 5 (two minute spots), and with sub-apical spots in spaces 6 to 8. On the hindwing upperside, there are spots in spaces 1b, 2, 3 and conjoined spots in spaces 4 and 5. The hindwing underside has the basal half silvery white below vein 8. The abdomen is dark brown, white banded above and entirely white beneath. On the upperside of the forewing, the male has a narrow arcuate whitish brand from just below vein 2 to before the origin of vein 3.

A view of the upperside of a male Eetia elia showing its brand.

Field Observations of Butterfly Behaviour:
This species is rarely encountered in Singapore. Past sighting locations of the adults include various parts of the Central Catchment Area such as MacRitchie Nature Trail, Sime Forest and Upper Seletar Reservoir Park. As typical with other skippers, the adults fly with swift and darting flights.

Early Stages:
Thus far, only one local host plant has been identified. The plant is Sarcotheca griffithii, a rare plant species mainly found in the central catchment reserve.

Host plant:Sarcotheca griffithii.

Close-up view of leaves of Sarcotheca griffithii.

The eggs are laid singly on the leaf upperside of the host plant. Each egg is mostly pink and has a darker shade of pink at the micropylar area. It is spherical with a flattened base and has a surface covered with a fine mesh of short wavy lines. The diameter is about 0.9mm.

Two views of an egg of Eetia elia

Mature egg with a faint view of the head (left), empty egg shell (right).

It takes 3 days for the collected egg to hatch. The young caterpillar eats just enough of the shell to emerge, and has a length of about 2.5mm. It has the typical cylindrical shape for skipper caterpillars, and a large black head. The body colour of the 1st instar could range from yellow to orange as depicted below.

1st instar caterpillar, length: 2.5mm.

After a quick exit and look around, the young caterpillar returns to the remnant of the egg shell to munch away more of the egg shell for its first meal. It does not finish the entire egg shell and soon makes its way to the leaf edge to construct its first leaf shelter. It rests within the shelter and ventures out to eat the leaf surface nearby and parts of the shelter. With additional cuts to the leaf flap and further silk threading work, the shelters for the first instar (and second instar) caterpillars soon assume a convex and tent-like appearance.

1st instar caterpillar, 4mm.

The tent-like leaf shelter for a late 1st instar caterpillar.

As with some other skipper species, Eetion elia caterpillars have been observed to ballistically eject their faecal pellets (frass) at speed, ensuring that the pellets are displaced as far away as possible from the shelter. This is believed to be a self-defense strategy, preventing potential predators or parasitoids from following the chemical signature of the frass to the originator.

2nd instar caterpillar, early in this stage, length: 7mm.

After 3 days in 1st instar and reaching a length of about 5mm, the caterpillar moults to the next instar within the shelter. The 2nd instar caterpillar is yellow with a green undertone. It reaches a length of about 9mm after 3 days of growth in this instar. The 3rd instar caterpillar has similar appearance as in the previous instar. As it grows, the body takes on bands of transverse ring patterns alternated with bands of smooth skin. The 3rd instar lasts about 5 days with the body length reaches 14-15mm. The leaf shelters for the larger caterpillars in 3rd and later instars are made from bringing two edges of the leaf together with sinuous cuts and silk threads, resulting in a ``curry puff'' appearance. The caterpillars eat the leaf adjacent to the shelter as well as the edges of the shelter.

3rd instar caterpillar, early in this stage, length: 9mm.

3rd instar caterpillar, late in this stage, length: 15mm.

Leaf shelter for a 3rd instar caterpillar over a 2-day period.

The 4th instar caterpillar has a rather different looking head capsule. There are three large and dark brown spots set among a light brown base colour. This instar takes about 5 days to complete with the body length reaching 23-24mm.

4th instar caterpillar.

5th instar caterpillar, early in this stage, 26mm.

The head capsule of the final and 5th instar caterpillar has an orange base color, and has all three black spots well defined and set within rings of beige coloration. This stage takes about 9-10 days to complete with the body length reaching 40mm.

5th instar caterpillar, late in this stage, length: 40mm.

At the end of 5th instar, the body of the caterpillar shrinks in length. Soon it becomes dormant in its leaf shelter and enters the prepupatory phase which lasts for one day.

Pre-pupatory larva of the White Spot Palmer.

Pupation takes place within the leaf shelter. The pupa secures itself with its cremaster attached to a short transverse band on the leaf surface, and has a silk girdle. The pupa is mostly pale green in base colour. It has a short thorax, a rather long abdomen, a long and pointed rostrum. There is also a pair of small but distinct orange-brown patches on the anterior part of the mesothorax. Length of pupae: 30-34mm.

Fresh pupa of the White Spot Palmer.

After 9 days, the pupa becomes mostly black in color with spots on the forewing upperside visible through the now transparent skin. Eclosion takes place the next day.

Mature pupa of the White Spot Palmer.

A newly eclosed White Spot Palmer.

Another newly eclosed White Spot Palmer.

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

Return of the No Brand Grass Yellow

Return of the No Brand Grass Yellow
(Eurema brigitta senna)

The genus Eurema is represented by at least six species in Singapore. These Grass Yellows are generally abundant - sometimes in large numbers congregating at puddling spots, and in some years, obviously noticeable when they fly in numbers in various areas in Singapore.

In Oct 2006, whilst photographing the newly-discovered Tawny Coster at an open wasteland in the north-eastern part of Singapore, ButterflyCircle members observed a small colony of Grass Yellows flying in the vicinity of some Leguminous bushes.

The host plant, which appeared familiar at first, was however different from the typical Mimosa spp that is usually found in these wastelands. Also, this plant did not possess the thorny stems present in the Mimosa. Upon scrutinising some of the photos taken of this Grass Yellow, it was discovered that this species was the No Brand Grass Yellow (Eurema brigitta senna). Despite its rather unglamorous name, this species was not recorded in recent years until this chance re-discovery.

So the conclusion is that this species, previously on the checklist by the early authors' records, has now been re-discovered by ButterflyCircle and the species re-instated on the Singapore Butterfly Checklist again!

Cassia mimosoides

Its host plant, Cassia mimosoides, is described as a "An exceedingly variable, prostrate to erect legume up to 1.5 m high, usually annual, sometimes with stems becoming woody above ground level and enabling the plant to perenniate. Stems variable, usually puberulent with short curved hairs, sometimes more or less densely clothed with longer spreading hairs. Inflorescence supra-axillary or sometimes axillary, one- to three-flowered. Pedicels 0.3 to 2.5 (3.0) cm long, usually shortly puberulent, sometimes spreading hairy. Petals yellow, obovate 4 to 13 mm long, 2 to 9 mm wide."

The No Brand Grass Yellow (Eurema brigitta senna)

The physical characteristics of the No Brand Grass Yellow are quite unique and the species is quite easy to differentiate from its lookalike cousins - the other Grass Yellows found in Singapore.

The underside forewings are without cell spots. Upperside forewing black apical border serrated, but not more deeply excavated in spaces 2 and 3. Females are slightly more unique in that the yellow colour of the hindwings are lighter than the forewings on the undersides. The males' undersides are unicolourous as with the other species of this genus.

A particularly 'heavily-freckled' male No Brand Grass Yellow resting in the shade

Both sexes undersides are covered with small brown 'freckles' which give the wings a rather spotted appearance, as compared to the other species in the genus. In certain individuals, the freckles are distinctly pronounced as to give the butterfly a very uniquely heavily spotted appearance, almost obscuring the clean yellow background colour of the wings.

A female No Brand Grass Yellow ovipositing on a leaf of its host plant

The caterpillars are light green with a lateral grey dorsal stripe and a yellow-green lateral stripe through the length of its body. The caterpillar feeds on the small leaflets of the host plant and stays on the mid-rib of the bi-pinnate leaves, eating voraciously.

Caterpillars of the No Brand Grass Yellow on the host plant, Cassia mimosoides

The life history is rather short, and this may account for the survival of the species over the past one and a half years at the site where the host plant is found. The caterpillar pupates on the host plant itself and can be found upright, suspended by a girdle, along the vertical stems of the plant.

An empty pupal shell of the No Brand Grass Yellow on the stem of the host plant after eclosion of the adult butterfly

The No Brand Grass Yellow has managed to survive at the host plant site for over a year and a half after its first sighting. The fate of this species hangs in the balance, as it is critically dependent on the availability of the host plant in an area which is slated for future residential development. For how long the site will be kept in its "wasteland" status is unknown, but in Singapore, the site is unlikely to be left status quo indefinitely.

Perhaps a programme for the cultivation of the host plant in a few protected areas in the nature reserves should be considered, if this species is to be conserved and continue its existence as part of the fauna of Singapore.

Text & Photos by Khew SK

References :

• Keng, H. (1990) Concise Flora of Singapore
• The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society.
• Butterflies of West Malaysia and Singapore, W.A. Fleming, 2nd Edition, Longman

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