25 May 2008

Life History of the Malayan Bush Brown

Life History of the Malayan Bush Brown (Mycalesis fusca fusca)



Butterfly Biodata:
Genus: Mycalesis Hübner, 1818
Species: fusca C. & R. Felder, 1860
Subspecies: fusca C. & R. Felder, 1860
Wingspan of Adult Butterfly: 45mm
Caterpillar Host Plant: Scleria bancana


Physical Description of Adult Butterfly:
Underneath, both wings are yellowish brown in ground colour, with two reddish/orangy brown longitudinal stripes crossing from the upper to lower edges, and a series of moderate to small ringed spots (ocelli) in the submarginal area. The post-discal area of the hindwing carries a reddish brown coloration. Above, the male is brown with obscure post-discal ocelli while the female is pale brown with more distinct post-discal ocelli. The female is typically larger in size.

Field Observations of Butterfly Behaviour:
This species is one of the less common of the Mycalesis genus in Singapore, and thanks to its more striking undersides, it is also one of the more distinctive members of this genus which typically features dull brown adults. Local sighting locations include the Central Catchment Nature Reserve and the Bukit Timah Nature Reserve. Individuals are usually encountered flying alongside forest trails or lurking in shady undergrowth in the vicinity of its host plant. As with other Satyrinae members, the adults fly in an erratic and jerky manner as their wings are closed for a relatively long period during flights.

Early Stages:
The host plant is a member of the Cyperaceae (Sedge) family, a grass-like herb with triangular stems and 3-ranked leaves with sheaths. This plant is rather common in the Nature Reserves and even along trails in the Southern Ridges.


Host plant : Scleria bancana

The eggs of the Malayan Bush Brown are laid singly on the grass leaf blade. Each egg is more or less spherical (about 1mm in diameter) and light translucent yellow. It appears to be smooth to the naked eyes, but faintly sculptured with a hexagonal reticulum when viewed with a more extreme close-up camera set-up.


A fresh egg of Malayan Bush Brown

The egg takes 4 days to mature. The young caterpillar pushes its way through the cracked egg shell, and then proceeds to eat up the egg shell almost entirely. It has a spindle-shaped body in light creamy yellow colour, and an initial body length of about 4mm. The body has rugose and ill defined segments. There is a pair of backward-pointing anal projections and a black head with a pair of short and rounded horns on the head. The young caterpillar eats the leaf blade along the edge. Caterpillars of all instars are observed to be sluggish in movement. They tend to rest lengthwise on the underside of a leaf during pauses between feeds.


Mature egg with the head about to break through the shell


Newly hatched 1st instar caterpillar, length: 4mm

The first instar lasts 4 days with the body length increases to about 6mm before the inevitable moult. With the change of instar, the two cephalic on the head become pointed and the two anal projections longer and thus pronounced. The body colour is yellow with a green undertone. The head and body is also roughened by numerous minute tubercles, each with a single seta. Faint longitudinal lines are also distinguishable on the body.


2nd instar caterpillar, early in this stage, 6.5mm


2nd instar caterpillar, late in this stage, length: 10mm

The 2nd instar lasts for 4 days with the body length reaches about 11mm before the next moult. The 3rd instar caterpillar mostly resembles the previous instar except for having longer anal projections and more prominent longitudinal lines on its body. This stage also takes 4 days to complete with body length reaching about 16mm.



3rd instar caterpillar, early in this stage, length: 11mm


3rd instar caterpillar, late in this stage, length: 13mm

One obvious change in the 4th instar caterpillar is in the head where the "face" area has changed from dark brown to yellowish green while the forward-facing portions of the horns remaining dark brown. The 4th instar lasts about 5 days with body length reaching 22-23mm.



4th instar caterpillar, length: 16mm

The next moult brings the caterpillar to its 5th and final instar. Now the "face" area of the head is pale yellow in colour and decorated with three pairs of curved brown lines. The body is dotted with several prominent black spots, and the longitudinal lines become more striking with alternating and varying shades of brown and green. In a period of 9 days, the body grows at a faster pace to a maximum length of about 40-42mm.


5th instar caterpillar, early in the stage, 30mm



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

Toward the end of 5th instar, the body gradually shrinks in length and becomes paler in colouration. Finally the caterpillar finds a spot on the underside of a leaf blade to secure itself at the anal end. The dormant pre-pupatory pose is complete once it has its body curved up and the head touches part of the body.


Preparatory pupa of Malayan Bush Brown

After one day as a pre-pupa, pupation takes place. The smooth pupa is light woody brown with faint brown markings. It is somewhat angular, with a dorsal keel on the thorax and ridges defining the dorsal wing margins. Length of pupae: 15-16mm.


Fresh pupa of Malayan Bush Brown

After 9 days of development, the pupa becomes darkened in color especially at the wing pads (corresponding to the dark brown uppersides of the forewings). The next day the eclosion event takes place with the adult butterfly emerges to start the next life cycle.


Mature pupa of Malayan Bush Brown



A newly eclosed Malayan Bush Brown

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 Press 1999
Text and Photos by Horace Tan

16 May 2008

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

11 May 2008

Life History of Eetion elia

Life History of the White Spot Palmer (Eetion elia)


Butterfly Biodata:
Genus: Eetion de Nicéville, 1895
Species: elia Hewitson, 1866
Wingspan of Adult Butterfly: 38mm
Caterpillar Host Plants:
Cleistanthus sumatranus (tentative, to be confirmed)

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:


Host plant

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 Eetion elia

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 Eetion elia

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 Eetion elia



A newly eclosed Eetion elia


Another newly eclosed Eetion elia

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

04 May 2008

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