31 July 2010

Life History of the Common Sailor

Life History of the Common Sailor (Neptis hylas papaja)

Butterfly Biodata:
Genus: Neptis Fabricius, 1807
Species: hylas Linnaeus, 1758
papaja Moore, 1875
Wingspan of Adult Butterfly: 50mm

Caterpillar Local Host Plants: Calopogonium mucunoides (Fabaceae), Canavalia cathartica (Fabaceae), Aeschynomene americana (Fabaceae), Senna alata (Fabaceae), Psophocarpus tetragonolobus (Fabaceae), Centrosema molle (Fabaceae).

A Common Sailor enjoying ripened fruits of the Singapore Rhododendron.

A Common Sailor sunbathinng on a cluster of flower buds of the Singapore Rhododendron.

Physical Description of Adult Butterfly:
On both wings the cells are open, and vein 8 on the hindwing ends on the costa. Above, the wings are dark brown to black in ground colour and feature the usual white markings for Sailor species. A distinguishing feature is that post-discal spots in spaces 2 and 3 of the forewing are in echelon and are directed to the termen. There is no whitish ring on the abdomen. Underneath, the wings are rich golden ochreous in ground color, and nearly all white markings prominently outlined with black borders.

A Common Sailor resting on a perch.

Field Observations of Butterfly Behaviour: This species is rather common in Singapore, and has a wide distribution across the main Singapore island. The adults can be found along the fringes of nature reserves and in many wastelands where its multiple host plants grow in abundance. As with other Sailor species, the Common Sailor adults are sun-loving and fly in a slow "sailing" fashion. They also visit flowers and ripening fruits for energy intakes. Adults can be easily confused with those of the Short Banded Sailor on the upperside, but the two can be differentiated with their drastically different undersides.

A mating pair of Common Sailor adults.

A sunbathing Common Sailor in a wasteland.

Early Stages:
Throughout its wide range of occurrence globally, Common Sailor is highly polyphagous with its early stages feeding on leaves of various plant species in the families: Leguminosae, Malvaceae and Tiliaceae
. In Singapore, so far five plants in the Leguminosae family have been recorded as larval hosts. Three of these plants (see pictures attached below) are readily found in wastelands, thus allowing the Common Sailor to have a strong foothold in these habitats.

Another pair of the Common Sailor adults mating under the midday sun.

Caterpillars of the Common Sailor feed on mature leaves of the host plant. As with other Neptis spp., the early instars of the Common Sailor eat the lamina of each leaf from the tip, or from a damaged and protruding edge, with the midrib typically left uneaten and used as a resting site. It does not construct frass chain as is the case for the Chocolate Sailor. Rather it has the habit of
cutting and hanging leaf fragments for concealment as part of its feeding routine. In this regard, it is similar to the Short Banded Sailor.

Host plant: Canavalia cathartica.

Host plant: Calopogonium mucunoides.

Host plant: Aeschynomene americana.

The eggs of the Common Sailor are laid singly at the tip of a leaf on the host plant After landing on a selected leaf and concluding that it belongs to a suitable host, the female Common Sailor reverses along the leaf surface until its abdomen tip reaches the leaf tip. At this moment, an egg is then deposited.

Two views of an egg laid at a leaf tip of Calopogonium mucunoides. Base diameter: 0.9mm.
Each egg is somewhat globular in shape, with the surface marked with hexagonal pits and and thin spines at pit corners. The micropylar sits atop. Freshly laid eggs are green in colour, but turning pale green and then yellowish when maturing. Each egg has a base diameter of about 0.9mm and a height about 1mm.

Two views of a mature egg.

The egg takes about 3-3.5 days to hatch. The young caterpillar emerges by eating away part of the egg shell. Measuring about 2.2mm in length, the newly hatched proceeds to consume the remaining egg shell as its first meal. Its cylindrical dark green body is covered with many small tubercles and short setae. The head capsule is brown to pale brown and dotted with a few short setae.

Two views of a newly hatched caterpillar, length: 2.2mm.

Four pairs of subdorsal tubercles, found on the 2nd and 3rd thoracic segments, 2nd and 8th abdominal segments, become somewhat larger than the rest as the caterpillar grows in this instar. These will go on to become more prominent branched spines in later instars. After reaching about 4.5mm in 2.5-3 days, the caterpillar moults to the 2nd instar.

Two views of a 1st instar caterpillar resting on the midrib, length: 4mm.

1st instar caterpillar doing maintenance work on a leaf fragment.

The body color of the 2nd instar caterpillar is yellowish green to dull green with many tiny pale tubercles covering its body surface. Obscure and oblique dark patches appear laterally. White-tipped branched spines, still short in length and yellowish brown in colour, replaces the four pairs of subdorsal tubercles seen in the 1st instar. The pale yellowish brown head capsule is now more elongated vertically, and its surface is dotted with a number of whitish conical tubercles amongst with the pair near the apex is the longest. This instar lasts about 2-3 days with the body length reaching about 6.5-7.5mm.

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

Two views of a 2nd instar caterpillar, late in this stage, length: 6mm

A 2nd instar caterpillar making a sinuous cut across the lamina.

The 3rd instar caterpillar resembles the 2nd instar catepillar in most aspects. The four pairs of subdorsal spines are much longer and larger, with the pair on the 3rd thoracic segment longest, and the pairs on the 2nd thoracic and the 8th abdominal segments second longest. Its dark head capsule is proportionately longer vertically, and the pair of apical spines now longer, more pointed and yellow-brown tipped.

Two views of a 3rd instar caterpillar, early in this instar stage, length:7mm

In the later part of the 3rd instar, the body color takes on a strong greenish tone. Dark lateral shadings just below the 2nd abdominal segment and on the 4th abdominal segment become more prominent. The dorsal saddle is now more distinctly outlined at the posterior segments with the saddle being in much lighter shade there. White to pale greenish lateral patches also appear on the posterior abdominal segments. This instar takes about 2.5-3.5 days to complete with body length reaching about 11-12mm.

Two views of 3rd instar caterpillar, later in this stage, length: 10.5mm.

The 4th instar caterpillar resembles the 3rd instar caterpillar. Laterally oblique dark streaks are seen in the dorsal saddle in the 1st to 4th abdominal segments. The subdorsal white to pale yellowish spines are now longer and stand out against the dark green base colour of the body segments. Lateral patches on posterior abdominal segments are also larger and more prominent. This instar lasts 3-4 days with body length reaching about 16-17mm.

Top: a late L3 caterpillar prior to its moult. Bottom: soon after its moult to the 4th instar..

Two views of 4th instar caterpillar, late in this stage, length: 17mm
In the 5th instar, the subdorsal pairs are now pale pinkish. The 5th instar caterpillar has much larger and longer subdorsal spines on the 3rd thoracic segment. The two thoracic pairs are forward pointing, in contrast to the remaining 2 abdominal pairs which are rear-pointing. The dorsal saddle is initially pale brown, but becoming whitish with pale pink shading in the posterior, and featuring dark oblique patches laterally in the anterior. Lateral patches on the posterior abdominal segments are again larger and more prominent. Initially whitish, they turn lime green gradually in one to two days.

A 5th instar caterpilla, newly moulted, length: 15mm.

Two views of a 5th instar caterpillar, lengths: 20mm.

Two views of a 5th instar caterpillar, late in this stage, length: 24mm.
The 5th instar lasts for about 4-6 days, and the body length reaches up to about 25mm. On the last day, the color of the body decolorizes with whitish/pale areas taking on a pinky shading. The caterpillar ceases feeding and wanders around. Eventually it comes to a halt on the underside of a leaf where the caterpillar spins a silk mound on a chosen spot from which it soon hangs vertically to take on the pre-pupatory pose.

A pre-pupa of the Common Sailor.

Pupation Event of a Common Sailor caterpillar

Pupation takes place a day later. The pupa suspends itself via a cremastral attachment to the silk mound with no supporting silk girdle. It is almost entirely yellowish except for the thoracic area of the dorsum which is pale pinkish brown. One day after pupation, the body surface takes on a silvery sheen. The thoracic segments are rather large with wing cases dilated laterally. The dorsum of the thorax is angular. The head is bluntly cleft at its front edge with small pointed lateral vertices. The pupa has the ability to flex laterally when disturbed. Length of pupae: 16-18mm.

Three views of a pupa of the Common Sailor.

After about 5.5 days of development, the pupal turns dark as the development within the pupal case comes to an end. The white markings on the forewing uppersdies become visible thorugh the pupal skin. The next morning, the adult butterfly emerges from the pupal case.

Three views of a mature pupa.

A newly eclosed Common Sailor drying its wings on the empty pupal case.

A newly eclosed Common Sailor.

  • The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society.
Revision: Added host plant, Centrosema molle, on 21 Dec 2015.

Text by Horace Tan, Photos by Anthony Ong, Benedict Tay, Ellen Tan, Federick Ho, Ben Jin Tan and Horace Tan

24 July 2010

Butterfly of the Month - July 2010

Butterfly of the Month - July 2010
Horsfield's Baron (Tanaecia iapis puseda)

The month of July is famous in that it is the only month of the year that was first named after a human being - Julius Caesar in 46 BC. The month has 31 days, and in the northern hemisphere, it is usually the peak of the summer months and is the hottest month of the year.

However, in Singapore, like in 2009, the weather has been rather wet - exceptionally wet actually, where floods occurred persistently following some of the wettest days on record. It had some residents up in arms when flood waters inundated their homes and commercial premises more than once during the month! A symptom of global warming and climate change? We'll have to wait and see. In the meantime, park your cars on high ground!

If the first of July be rainy weather,
It will rain, more or less, for four weeks together.
Source: English Proverb

Despite the rainy weather, our butterfly friends continue to thrive. A moment's respite from the bad weather will see our winged jewels up and about, feeding hungrily at flowers and other sources of food.

This month, we feature the sexually dimorphic species, the Horsfield's Baron (Tanaecia iapis puseda). This species prefers the sanctuary of the forested areas in Singapore, although they are sometimes found in public parks and gardens. Males are more often seen than females. The male of this species exhibits 'territorial' behaviour, where it perches on a few favourite locations and dives to chase away any intruders into its space - even a stone thrown into its domain of supervision will be similarly chased away!

The male Horsfield Baron is a rich velvety black above with a broad bright blue marginal border on the hindwing and reaching the tornal area of the forewing. The underside is a pale buff with light brown markings.

The female is a pale ochreous brown resembling the Malay Viscount. The submarginal “V” shaped markings are less distinct than those of the associated species. In some individuals, light blue washes can be more distinct on the wings, especially on the white areas of the wings.

The male Horsfield Baron has a flap-glide flight and is skittish and alert to movements. Often, individuals are encountered where they return persistently to a few favourite perches time and again, even after being disturbed. It appears to prefer stopping to rest with its wings opened flat rather than with its wings closed upright. Very rarely, males have also been observed to puddle at roadside seepages.

A male Horsfield's Baron puddling at a roadside seepage

The female, on the other hand, is usually found flying amongst shrubbery and particularly its preferred caterpillar host plant - the Singapore Rhododendron (Melastoma malabathricum). The female is more often found feeding on flowering plants, rotting fruit and the ripened fruit pods of the Singapore Rhododendron.

The caterpillar is unique in appearance, with its 'spiky' processes making it appear much larger and sinister than it really is. It is actually quite harmless.

Where the species is found, sometimes several individuals are encountered. Whilst it cannot be said to be common, the Horsfield's Baron makes a regular appearance in many parts of the nature reserves and even in public parks and gardens.

Text by Khew SK ; Photos by James Chia, Sunny Chir, Federick Ho, Khew SK, Koh Cher Hern & Sum CM

17 July 2010

Life History of the Anderson's Grass Yellow

Life History of the Anderson's Grass Yellow (Eurema andersonii andersonii)

Butterfly Biodata:
Genus: Eurema
Hübner, 1819
Species: andersonii Moore, 1886
Subspecies: andersonii Moore, 1886
Wingspan of Adult Butterfly: 40mm
Caterpillar Local Host Plant:
One plant found in the Central Catchment Area (species ID to be determined). [21 July 2012: Plant identified as Ventilago maingayi; another host plant Ventilago malaccensis also recently recorded.]

An Anderson's Grass Yellow perching on a fern frond.

Physical Description of Adult Butterfly:
Above, the wings are lemon-yellow with the hindwing having a thin black border and the forewing having a thick black border which is deeply excavated between veins 2 and 4, but not more deeply excavated in space 2 than in space 3. The inner edge of the black border in spaces 1a and 1b inclined slightly towards the tornus. Underneath, the wings are yellow with several rusty brown spots. There is no spot at the base of space 7 on the hindwing, but a single spot is present in the forewing cell. Usually, a rather broad dark subapical stripe can be seen in the forewing. Males have an elongate patch (the brand) lying along the cubital vein on the forewing.

An Anderson's Grass Yellow having its mineral intake on a damp patch.

An Anderson's Grass Yellow perching on a grass blade.

Field Observations of Butterfly Behaviour: Anderson's Grass Yellow is not as commonly seen as its close cousin, Common Grass Yellow, (Eurema hecabe contubernalis) as it is mainly a forest denizen with sightings restricted to the Central Catchment Area (CCA). Where its host plant thrives within CCA, Anderson's Grass Yellow can be sighted with relative ease. Typically on a sunny day, adults can be seen fluttering along forest trials, visiting flowers, puddling on wet grounds and making oviposition visits to its host plant.

An Anderson's Grass Yellow taking nectar from flowers of mile-a-minute weed.

Another puddiling Anderson's Grass Yellow deep in the nature reserve.

Early Stages:
The host plant grows in relative abundance in certain areas within CCA. It appears to be a liana which has young leaves in dark to reddish brown, but turning green when they mature. The early stages of the Anderson's Grass Yellow feed on relatively young leaves of this host plant. Noteworthy is that the same plant is also utilized by early stages of the Tree Yellow (Gandaca harina distanti).

The host plant of Anderson's Grass Yellow with young leaves shown.

The eggs of the Anderson's Grass Yellow are laid singly on the surface of a young leaf of the host plant. The long spindle shaped egg is laid standing at one end with a length of about 1.1-1.2mm. It is creamy white in color and has many fine vertical ridges and numerous indistinct and intermittent horizontal ridge lines. The micropylar sits at the tip of the standing egg.

An egg of the Anderson's Grass Yellow sighted on a young leaf within the nature reserve.

A close-up view of an egg of the Anderson's Grass Yellow.
The egg takes about 2-3 days to hatch with the newly hatched eating away part of the egg shell to emerge. Measuring about 1.8-1.9mm in lenght, the newly hatched sports a creamy white head capsule and a cylindrical and pale whitish body covered with rows of tubercles running lengthwise. Each tubercle has a setae emerging from the middle of it. The two rows of tubercles flanking the dorsal line are much larger but with shorter setae than the rest. A miniscule droplet of fluid can be found at the tip of some of the setae.

A newly hatched caterpillar of the Anderson's Grass Yellow, length: 1.9mm.

The newly hatched has the rest of the empty egg shell as its first meal before moving on to eat the lamina of the young leaf. The body and the head become more yellowish as the caterpillar feeds and grows. The body also assumes a strong green undertone as the caterpillar grows to a length of about 4mm in about 2-2.5 days for this instar.

Two view of a 1st instar caterpillar, length 2.7mm.

The 2nd instar caterpillar have numerous setae-bearing tubercles on its body with the length of the setae proportionately shorter than in the first instar. The head capsule is yellowish green and sporting a few rather fine setae. This instar lasts about 2-3 days with the body length reaching 8mm.

Two view of a 2nd instar caterpillar, early in this stage, length: 3.5mm

Two late 2nd Instar caterpillars, moments before their respective moult to the next instar.

The 3rd instar caterpillar has a yellowish green body with a similarly-coloured head capsule. Its numerous setae are proportionately shorter compared to the previous instar. A closer scrutiny reveals that the body is essentially yellow in base colour, and each body segment has up to 6 rings of small tubercles which are green to dark green in colour. Typically each tubercle has one short and fine setae protruding from it, and the end of each setae has one tiny fluid droplet. A white lateral band is seen on either side of the body, rather faint at this stage. This instar takes about 1.5-2.0 days to complete with body length reaching about 11-12mm.

Two views of 3rd instar caterpillar, early in this stage, length: 7.5mm

A very late 3rd instar caterpillar, soon to moult to the 4th instar.

The appearance of the 4th instar caterpillar is little changed from the 3rd instar. The lateral whitish bands are broader and thus more prominent. This instar lasts 1.5-2.0 days with body length reaching about 18mm.

Two views of a 4th instar caterpillar resting on the midrib of a young leaf, early in this stage, length: 9.5mm.

A 4th instar caterpillar, late in thie stage, length: 18mm

The 5th and final instar caterpillar resembles the 4th instar caterpillar closely. The one visible change is in the lateral white bands which have become prominent and well defined in their outlines. The 5th instar lasts for 3-4 days, and the body length reaches up to 29mm.

Two views of a 5th instar caterpillar, length: 25mm.

A 5th instar caterpillar, length: 27mm.
On the last day of the 5th instar, the body of the caterpillar shortens and changes to a dull shade of pale green. It ceases feeding and comes to rest on the underside of a stem/stalk on the host plant. Here the caterpillar spins a silk pad and a silk girdle, with which the caterpillar soon become immobile in its pre-pupatory pose.

A pre-pupatory larva of the Anderson's Grass Yellow on a stem of the host plant.

Pupation takes place about 0.5 day later. The pupa secures itself with the same silk girdle as in the pre-pupal stage, but with cremaster replacing claspers in attaching the posterior end to the silk pad on the stem, The yellowish green pupa has a pointed head, a slight dorsal protrusion, and a large wing case tapering into a keel. A pale brown dorsal band, rather broad in width, runs from the anterior to the posterior end. A pale brown line also runs laterally on each side from the thorax to the posterior end. Length of pupae: 17mm.

Two views of a pupa of the Anderson's Grass Yellow.

Close-up on the cremastral attachment to the silk pad on the substrate.
The attachment is achieved through brown hooks on the cremaster catching the mesh of silk threads.

Two views of a mature pupa of the Anderson's Grass Yellow.
The now transparent wing pad show s the yellow forewing upperside with its black border

After about days 5.5-6.0 days of development, the pupal skin turns translucent as the development within the pupal case comes to an end. The yellow coloration and back borders on the forewing upperside are now discernible. The following day, the adult butterfly emerges from the pupa.

A newly eclosed Anderson's Grass Yellow drying its wings near its pupal case.

  • 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, Federick Ho, Khew SK and Horace Tan