Life History of the Yellow Streak Darter

Life History of the Yellow Streak Darter (Salanoemia tavoyana)



Butterfly Biodata:
Genus: Salanoemia Eliot, 1978
Species: tavoyana Evans, 1926
Wingspan of Adult Butterfly: 29-32mm
Caterpillar Host Plants: Licuala spinosa (Arecaceae, common name: Mangrove Fan Palm).


A Yellow Streak Darter taking nectar.


A Yellow Streak Darter sighted on a leaf perch.

Physical Description of Adult Butterfly:

Above, both sexes are dark brown with the forewing having a number of hyaline spots: two small sub-apical spots at the base of spaces 6 and 7, two large spots at the base of spaces 2 and 3, and two sub-equal spots in the cell. There is a yellow streak in the basal half or two-thirds on the forewing. Both sexes have a yellow discal patch on the hindwing and a yellow-colored costal margin, both of which are broader and more prominent in the male than in the female. In addition, the male has a sub-costal yellow streak in the basal half of the forewing, and a yellow-colored dorsal margin on the hindwing. Underneath, the wings are yellowish orange in base color with a number of irregularly-shaped post-discal black spots on both fore- and hindwings. Additional black spots are found in the cell and the base of spaces 1b, and 7 in the hindwing. Several of these spots take on the appearance of a yellow oval spots encircled in black. The blacks spots in the female are somewhat larger and more prominent than in the male.


The first sighting of a Yellow Streak Darter.

Another Yellow Streak Darter on a leaf perch.

Field Observations of Butterfly Behaviour:

This species was only recently discovered and added to the Singapore checklist as species #300. According to C&P4, the Malayan species of the genus Salanoemia are all very rare, and the Yellow Streak Darter is no exception. In Singapore, adult sightings have so far been very rare and only confined to the offshore island, Pulau Ubin.

A male Yellow Streak Darter.


A female Yellow Streak Darter.

Early Stages:


Host plant: Licuala spinosa.

The host plant, Licuala spinosa, is a palm with fan-like leaf in a pinwheel layout. The petiole is armed with spines. This plant can be found growing in back mangrove habitats or in gardens/parks as an ornamental and landscaping plant. The caterpillars of the Yellow Streak Darter feed on leaves of this plant, and live in shelters made by joining edges of leaf fragments together with silk threads.

A leaf shelter of a final instar caterpillar of the Yellow Streak Darter.

The eggs are laid singly on the leaf of the host plant. Each hemispherical egg has four concentric colored zones, starting from the centre and moving outwards, the colors are dark pinky red, reddish brown, pinky white and finally dark pink red. The micropylar sits atop. There are 20 disheveled radial ridges in all. The base diameter is about 1.4mm.


Two views of an egg of the Yellow Streak Darter.


A mature egg with the young caterpillar already nibbled away the polar part of the egg shell.

It takes about 4 days for the collected egg to hatch. The young caterpillar eats just enough of the shell to emerge, and has a length of about 3mm. Its has a cylindrical body shape, very short dorso-lateral and sub-spiracular setae and a tuff of long setae at the posterior end. The body is mainly orange in base color with faint reddish bands running dorso-laterally. The head capsule is yellowish brown.

A newly hatched 1st instar caterpillar with its empty egg shell nearby.


Two views of a newly hatched caterpillar, length: 3mm.

The body color changes to pale yellowish green after a few feeding sessions on the leaf. The newly hatched constructs its leaf shelter as one of its first tasks after the hatching. Between feedings, the caterpillar retreats to its shelter for rest and security. By the time the caterpillar lies dormant in its shelter for the moult to the 2nd instar, its length has reached about 5mm. The 1st instar takes about 2-3 days to complete.

1st instar caterpillar, late in this stage, dormant prior to its moult, length: 5mm.

The 2nd instar caterpillar is whitish, but appears to be yellowish green with its "stomach" contents showing through the translucent cuticle. The short dorso-lateral and lateral setae are now absent. The anal plate still carries a few setae but these are not as long and prominent as in the 1st instar. The head is pale yellowish brown. This instar lasts about 3-4 days with the body length reaching about 8mm.

Two views of a 2nd instar caterpillar, early in this stage, length: 4.5mm.


A 2nd instar caterpillar hard at work at carving out a leaf fragment. The fragment (with a small portion not cut) will be joined to the uncut portion to form its shelter.


Two views of a 2nd instar caterpillar, late in this stage, length: 7.5mm.

The 3nd instar caterpillar resembles the 2nd instar caterpillar closely in body markings and coloration. This instar lasts about 5-7 days with the body length reaching about 11mm.

Two views of a 3rd instar caterpillar, female, early in this stage, length: 6.8mm.


Two views of a 3nd instar caterpillar, later in this stage. length: 9.5mm.

The 4th instar caterpillar is pale yellowish white in body color with a light green undertone. The head capsule is pale beige brown with two lateral white stripes sitting just above the mouth parts. Dark brown meshed markings adorn the surface above the white stripes. This penultimate instar lasts 5-7 days with the body length reaching up to about 18mm.

Two views of a 4th instar caterpillar, female, length: 17mm.


A 4th instar caterpillar, male, late in this stage, length: 19mm.

The 5th (and final) instar caterpillar closely resembles the 4th instar caterpillar with few variations. The head capsule has a base color ranging from pale beige brown to greyish white, and it appears to have more extensive black meshed markings than in the previous instar. This instar takes about 9-10 days to complete with the body length reaching up to about 26mm. On the last one to two days of this instar, the still feeding caterpillar secretes a thin layer of whitish substance on the lower sides of its body.

A newly moulted 5th instar caterpillar.


Two views of a 5th instar caterpillar, length: 24mm.


A 5th instar caterpillar, male, late in this intar, length: 26mm.


A 5th instar caterpillar in the field. Hard at work in repairing its damaged leaf shelter.

Towards the end of the 5th instar, the the body of the caterpillar shortens and its coloration changes to a translucent pale green. Soon it becomes dormant in its leaf shelter and enters the prepupatory phase which lasts for one day During this time period a copious amount of white waxy substance is deposited within the tight confine of the leaf shelter.

A pre-pupa of the Yellow Streak Darter.

Pupation takes place within the leaf shelter. The pupa does not secure itself with any cremastral attachment nor any silk girdle. It is pale brown in the anterior end, pale greenish in the rear thorax and wing cases, and pale yellowish brown in the abdomen. Length of pupae: 14.5-17.5mm.


Two views of a pupa of the Yellow Streak Darter.

On the last day of the pupal period, the pupa becomes mostly brown to dark brown. Yellow markings against a dark brown background are now visible in the wing cases. Finally after about 8 days of pupal phase, eclosion takes place with the adult emerging from the pupal case.


Two views of a mature pupa of the Yellow Streak Darter.


A newly eclosed male Yellow Streak Darter.


A newly eclosed female Yellow Streak Darter.

References:

• [C&P4] 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 by Horace Tan, Photos by Simon Sng, Khew SK and Horace Tan.

Butterfly of the Month - August 2011

Butterfly of the Month - August 2011
The Common Lascar (Pantoporia hordonia hordonia)

Once again, we're back to the month of August, the eighth month of the year that was named in honour of Emperor Gaius Julius Caesar Augustus, who is considered the 1st Emperor of the Roman Empire.  He ruled the Empire from 27BC to AD14.  In Singapore, August is the month of its National Day, where on 9 Aug 1965, it separated from the Federation of Malaysia and became and independent republic. 

In 2011, multicultural Singapore, our Muslim friends celebrate Hari Raya Puasa (on 30 Aug)  whilst the Chinese community observe the Month of the Hungry Ghost, which ends on 28 Aug.  It's also a significant month in that, for the first time in the history of Singapore, the Presidential Elections feature a total of four candidates for the Presidency!  It will be an interesting polling day on 27 Aug 2011.

The birthstone for the month of August is the sardonyx, a variant of the stone onyx, where the coloured alternating bands in the stone are shades of reddish-orange.  Onyx is formed of bands of chalcedony in alternating colors. It is cryptocrystalline, consisting of fine intergrowths of the silica minerals quartz and moganite. Its bands are parallel to one another.

Wear a sardonyx or for thee,

No conjugal felicity;
The August-born without this stone,
`Tis said, must live unloved and lone.
- Gregorian Birthstone Poems

This month, we feature a small but irritatingly skittish butterfly (to us photographers), the Common Lascar.  The species is a forest-dependent species, and is usually found within the nature reserves of Singapore.  It is a relatively weak-flyer, but is skittish and quickly takes to the treetops if disturbed.  It has a distinctive flap-glide flight and usually stops to sunbathe on the tops of leaves at sunlit spots in the forested areas. 

It is often found in the vicinity of its host plant, the Petai (Parkia speciosa) which grows wild in the forested nature reserves.  The females of the Common Lascar have often been observed flying near its host plant, trying to oviposit on the young leaves of the plant. 

There are four lookalike Lascars extant in Singapore, and they are often difficult to identify when in flight.  The characteristics that separate the four species (of which two are in the genus Pantoporia and the other two in the genus Lasippa) generally occur in the forewing submarginal markings.

The Common Lascar features the typical alternate black-orange bands on the upperside of the wings.  However, unlike the other members of the lookalike Lascars, the Common Lascar is the only species that feature striated and marbled underside markings. The thick orange submarginal line on the upperside of the forewing also distinguishes it from the other similar looking Lascars.

The species is relatively common, particularly in local areas within the nature reserves where there are young plantlets of its host plant growing in the vicinity.  It has also been observed to puddle at damp spots on the forest floor, but is more frequently observed fluttering amongst the shaded forest understory, stopping with its wings opened flat on the tops of leaves. 

Text by Khew SK : Photos by Federick Ho, Khew SK; Tang HB & Horace Tan

Life History of the Common Birdwing

Life History of the Common Birdwing (Troides helena cerberus)

Butterfly Biodata:
Genus: Troides Hübner, 1819
Species: helena Linnaeus, 1758
Subspecies: cerberus C&R Felder, 1865
Wingspan of Adult Butterfly: 100-140mm
Local Caterpillar Host Plant: Aristolochia acuminata (Aristolochiaceae, common name: Indian Birthwort, Dutchman's Pipe) .



A female Common Birdwing taking nectar from Ixora in an urban hill park


Ar female Common Birdwing taking nectar from Pagoda Flower in a nature park.

Physical Description of Adult Butterfly:
The forewings of both sexes are black with veins typically edged with greyish streaks, more conspicuously so in the female. The hindwings are rick golden yellow with black veins and black borders. In addition, the female has a complete series of rather large submarginal black spots, while the male has just one or a few submarginal spots.


A male Common Birdwing.


A female Common Birdwing.

Field Observations of Butterfly Behaviour:
The Common Birdwing is uncommon in Singapore, and is usually found where its host plants are cultivated. The adults are strong flyers and are capable of flying long distances and at considerable height in a bird-like manner. The adults have been sighted both in forested areas as well as in urban parks and gardens. As is the case for many of the Papilionidae species, an adult taking nectar from flowers can flutter its forewings whiles its hindwings are kept relatively still.


A female Common Birdwing taking nectar from flowers of an Acacia sp.



Early Stages:
The sole recorded local host plant, Aristolochia acuminata, is a perennial vine and can be found cultivated in various locations locally. In the wild, this plant can also be found in forests and open lowland thickets. The caterpillars of the Common Birdwing feed on the leaves and the young shoots of this plant.


Host plant : Aristolochia acuminata.

A mating pair of the Common Birdwing.

The eggs of the Common Birdwing are typically laid singly on the leaf surface or the stem of the host plant. It is however not uncommon that eggs are also laid on nearby natural objects or artificial structures. The spherical egg has its surface coated with a non-uniform layer of orange-yellow or whitish granulated substance. Diameter: 1.9-2.0mm.


Two views of an orange-colored egg of the Common Birdwing.


Two views of a white-coated egg of the Common Birdwing


A mature egg of the Common Birdwing showing the young caterpillar chipping away at the egg shell.

The egg takes about 6 days to hatch. The young caterpillar eats its way out of the mature egg, and then proceeds to devour the rest of the egg shell. The newly hatched is about 4.5-4.8mm long and has a black head, rows of short dorsal-lateral and lateral tubercles with tufts of short setae emanating from the terminal ends. It is mainly reddish brown with orange coloration on the anterior and posterior segments, and on the 4th abdominal segment.


A newly hatched caterpillar eating the egg shell.


Two views of a 1st instar caterpillar, newly hatched, length: 4.5mm.

After about 2-3 days in 1st instar, the caterpillar moults to the next instar.


Two views of a late 1st instar caterpillar, about to moult to the next instar, length: 8mm.

The 2nd instar caterpillar has a similar appearance to the 1st instar caterpillar except for the longer and fleshy processes, now devoid of the tufts of setae at their terminal ends. These fleshy dorso-lateral processes are colored in pinky or salmon red for those on 2nd-3rd thoracic, 4th abdominal and last 3 abdominal segments. The 2nd instar lasts 2-3 days and the body length reaches up to about 11mm before the next moult.


Two views of a 2nd instar caterpillar, early in this stage, length: 8.5mm


2nd instar caterpillar, late in this stage, length: 11mm

The 3rd instar brings about the appearance of a pale pinkish or whitish saddle straddling the 3rd-4th abdominal segments. This instar takes 2-3 days to complete with body grown to about 21mm in length.


Two views of a 3rd instar caterpillar, length: 19mm.


Two views of a late 3rd instar caterpillar, about to moult to the next instar, length: 20mm.

The 4th instar caterpillar has a more prominent saddle in pale yellowish brown or white coloration. extensive white markings on it body. The white patch on the posterior abdominal segments has extended to the whole of abdominal segment 7 and white lateral patches appear on the thoracic segments. This instar lasts about 4 days with body length reaching about 33mm.


Two views of a 4th instar caterpillar, early in this stage, length 22.5mm.


Two views of a 4th instar caterpillar, late in this stage, length 33mm.

The next moult brings the caterpillar to the 5th and final instar. Featuring the same layout of the fleshy processes, the body is uniformly colored in coffee brown to dark brown with the saddle mark painted in a comparatively lighter shade of greyish brown.


Two views of a a 5th instar caterpillar, late in this stage, length: 53mm.


A 5th instar caterpillar chomping away at a young stem in the field.

The 5th instar lasts for about 5 days, and the body length reaches up to 57-60mm. Toward the end of this instar, the body gradually shortens in length. Eventually the caterpillar comes to rest on the lower surface of a stem. It then goes on to spin a silk pad and a silk girdle to secure itself and becomes a non-mobile pre-pupatory larva.


A pre-pupatory larva of Common Birdwing.

All instars of the Common Birdwing possess a fleshy organ called osmeterium in the prothoracic segment. Usually hidden, the orange-coloured osmeterium can be everted to surprise any intruder when the caterpillar senses a threat.


Partially everted osmeterium of a final intar Common Birdwing caterpillar

The osmeterium can still be everted at the early pre-pupal stage.

Pupation takes place a day later. The upright pupa suspends itself with a silk girdle from the stem. with its cremaster attached to the silk pad at the lower end. The pupa resembles a rolled-up leaf with a length of about 43-45mm long. There are two colours form: green and brown.

A Common Birdwing caterpillar molts to its pupal stage.

Two colour forms of the Common Birdwing pupa. Dorsal views.

Two colour forms of the Common Birdwing pupa, side views.

After 19-20 days, the pupa turns black as the development within the pupal case draws to a close. The next morning the adult butterfly emerges from the pupal case.


A mature pupa of the Common Birdwing.

An eclosion sequence of the Common Birdwing.

A newly eclosed Common Birdwing clinging on to its empty pupal case.

References:

• [C&P4] 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 by Horace Tan, Photos by Terry Ong, James Chia, Bobby Mun, Loke PF, Anthony Wong, Khew SK and Horace Tan