Larval Host Plant for Butterflies: Yellow Cow Wood

Butterflies' Larval Host Plants #7
The Yellow Cow Wood (Cratoxylum cochinchinense)

This 7th instalment of our Butterflies' Larval Host Plants series features Cratoxylum cochinchinense (Yellow Cow Wood), a species of the family Hypericaceae (St. John's-Wort Family). The species name "cochinchinense" has the Latin meaning "of Cochinchina" which refers to the region comprising the southern third of Vietnam.

Across Southeast Asia and Southern China, C. cochinchinense has been found to grow in multiple habitats including primary and secondary forests, grasslands and woodlands etc. In Singapore, it is more likely to see it being cultivated in parks and gardens as ornamental plants. Individual wild specimens can also be found in the Central Catchment Reserve and Bukit Timah Reserve, and a number of other locations. Various parts of the plant have found uses in different aspects of human lives. One example is in Traditional Chinese Medicine: The roots, bark, and twigs are used a medicine for treating cold and diarrhea.

Plant Biodata :
Family : Hypericaceae
Genus : Cratoxylum
Species : cochinchinense
Synonyms : Hypericum cochinchinense, Ancistrolobus ligustrinus, Cratoxylum biflorum, C. chinense , C. ligustrinum, C. petiolatum, C. polyanthum.
Country/Region of Origin :  Southeast Asia, Southern China
English Common Name : Yellow Cow Wood
Other Local Names :  Kayu Arang, Kemutong, Tree-Avens, 黃牛木
Larval Host for Butterfly Species: Eurema hecabe contubernalis (Common Grass Yellow), Lexias pardalis dirteana (Archduke), Phaedyma columella singa (Short Banded Sailor).

Left: A cultivated Yellow Cow Wood in the car park at Dairy Farm Nature Park. Right: A wild Yellow Cow Wood in the Bukit Timah Nature Reserve. Note the distinctive orange-brown trunks.

Yellow Cow Wood is a deciduous plant occurring in either shrub or tree form, with the latter ranging from 1.5m to 18m tall, occasionally up to 33m tall.  The bark is smooth, grey-brown to orange-brown, and is a source of a brown dye. The trunk is hard and durable and is harvested for timber usage when the tree has grown to a suitable size.

Closer view of the orange-brown trunk of two Yellow Cow Wood tree.

The leaves are elliptic or lanceolate in shape, 3-10cm in length and 1-4 cm in width. They are oppositely arranged. Young leaves are initially reddish, then turning reddish brown, yellow green to grayish green when fully developed. In some places, young shoots are eaten as raw vegetable, and young leaves are used as a substitute for tea.

Drooping branches of Yellow Cow Wood showing leaves in various stage of development.

A closer view of a leaf branch of Yellow Cow Wood showing leaves in various stage of development.

The opposite arrangement of leaves on a branch.

A reddish young leaf.

A yellowish-green maturing leaf.

A green mature leaf.

Flowers of the Yellow Cow Wood are small, 1-1.5cm in diameter, dark red to pink, and occur in axillary or terminal cymes. These bisexual flowers attract insects such as bees and hoverflies to act as pollinators in the reproduction process.

Flower buds and a flower of the Yellow Cow Wood.

Cymes bearing blooming flowers of the Yellow Cow Wood, with a visitor.

A closer view of flowers of the Yellow Cow Wood.

Fruits are small, up to 1.2cm long. The young fruits are green in colour and are used as a spice for cooking. Mature fruits are dark brown. When ripened, the fruit opens up to reveal three seed-bearing loculi. Each loculus contains 5-8 seeds which are unilaterally winged.

Young fruits of the Yellow Cow Wood.

Mature fruits of the Yellow Cow WOod.

Close-up view of ripened fruits of the Yellow Cow Wood, with stack of seeds indicated.

Seeds of the Yellow Cow Wood.

Close-up views of a seed of the Yellow Cow Wood.

In Singapore, the Yellow Cow Wood also serves as the larval host plant for three butterfly species: Common Grass Yellow, Archduke and  Short Banded Sailor. The first is a Pierid and the last two are Limenitid.

A Common Grass Yellow.

An Archduke (male).

A Short Banded Sailor.

Eggs of the Common Grass Yellow are laid on the reddish young leaves of the Yellow Cow Wood, whereas those of Archduke are laid on leaf surface (both upper and undersides) of both young and mature leaves. In contrast, eggs of the Short Banded Sailor are typically laid at the tip of a mature leaf.

A female Common Grass Yellow laying an egg on a young leaf of the Yellow Cow Wood.

An egg of the Common Grass Yellow found on a young leaf of the Yellow Cow Wood.

A female Archduke laying an egg on the underside of a leaf of the Yellow Cow Wood.

A cluster of six eggs of the Archduke found on the upperside of a young leaf of the Yellow Cow Wood.

Caterpillars of the Common Grass Yellow feed on leaves on young shoots of the Yellow Cow Wood whereas those of the Archduke and Short Banded Sailor feed on the developing and mature leaves. The early instar caterpillars of the Short Banded Sailor has the habit of feeding from the leaf tip, cutting and hanging leaf fragments as they munch on.

A young caterpillar of the Short Banded Sailor resting at the leaf tip. Hanging leaf fragments can be seen further up.

A final instar caterpillar of the Short Banded Sailor.

Two views of a final instar caterpillar of the Common Grass Yellow.

A caterpillar of the Common Grass Yellow resting on a leaf of the Yellow Cow Wood in an Eco Garden.

A later instar caterpillar of the Archduke on a mature leaf of the Yellow Cow Wood.

Caterpillars of the Common Grass Yellow and the Short Banded Sailor typically pupate on the underside of a stem, whereas those of the Archduke do so on the underside of a leaf.

Two views of a pupa of the Common Grass Yellow on the underside of a stem.

Three views of a pupa of the Short Banded Sailor.

A pupa of the Archduke on the midrib on the underside of a leaf.

References:

• The Concise Flora of Singapore : Hsuan Keng Singapore University Press, 1990.
• Asianplant.net - Cratoxylum cochinchinense.
• Nature Loves You - Cratoxylum cochinchinense.
• Useful Tropical Plants - Cratoxylum cochinchinense.
• Wikipedia - Cratoxylum cochinchinense.
• Go Botany - Hypericaceae.

Text and Photos by Horace Tan.

Singapore's Long-Tailed Hairstreaks

Singapore's Long-Tailed Hairstreaks
The Magnificent Seven - Part 1

In the 2nd Edition of the Field Guide to the Butterflies of Singapore (2015), the taxonomic classification of the Lycaenidae family has been updated to be consistent with more recent and contemporary literature on this family of butterflies. This group comprises many small but beautiful butterflies that are often coloured a range of iridescent greens, blues and purples. Many are attractively coloured in bright hues whilst others possess tails.

The Lycaenidae in Singapore are represented by six sub-families. These are Curetinae (the Sunbeams), Poritiinae (the Gems), Miletinae (the Harvesters), Aphnaeinae (the Silverlines), Polyommatinae (the Blues) and Theclinae (the Hairstreaks). A common feature of the latter three sub-families is that their wings are "designed" to fool predators into attacking the wrong side of the butterflies. Often sporting tails and adorned with false "eyes" on their hindwings, many species of this sub-families display what is often referred to as "decoy protective strategy".

In particular, the Theclinae, collectively referred to as Hairstreaks, display this decoy characteristic in the majority of the species in the sub-family. In some cases, the decoy is carried to the extreme where the species feature extremely long tails (>10mm long) that appear to be alive as they twirl in the breeze when the butterfly is perched to rest. This blog article (in two parts) introduces our readers to 7 of these long-tailed Hairstreaks found in Singapore.

I have always been amused when our butterfly-crazy friends from Hong Kong visit Singapore, and seeing how happy they were, whenever they encounter one of our long-tailed hairstreaks. Then I realised that amongst the Lycaenidae in Hong Kong, there are no extant long-tailed species there! Perhaps that is why our Hong Kong friends get rather excited when they see these species here in Singapore. We do hope our HK friends would visit us more often to enjoy our butterflies here. 

Part 1 of this blog article showcases 3 of these spectacular long-tailed hairstreaks that can be found in Singapore.

The Branded Imperial (Eooxylides tharis distanti)

A pair of Branded Imperials perched on a young shoot of its caterpillar host plant.  Note the eggs.

A forest-dependent species, the Branded Imperial does not often venture out into urban parks and gardens. They are usually found along the fringes of our forested nature reserves where its preferred caterpillar host plant, Smilax bracteata, a non-native invasive "weed" that is now common in our forests. The signature reddish-orange underside with the unmarked forewing with the hindwing featuring black and white tornal area easily distinguishes the Branded Imperial from the other species in the sub-family.

A Branded Imperial feeding on the secretions of its host plant, Smilax bracteata

The hindwing sports three tails - one long tail at vein 2 of the hindwing and two shorter tails at veins 1a and 3. The upperside is black, with a similar-patterned hindwing tornal area like its underside. The Branded Imperial can be considered common, and is often spotted in shaded areas in our forests. In some areas where they can be found regularly, there are often several individuals seen together.

The butterfly has a "hopping" flight as they flit amongst the shrubbery. They often stop to rest with their wings folded upright. Occasionally, several individuals can be seen together as they feed on the secretions on the young shoots of their host plant. The life history of the Branded Imperial has been recorded and the full documentation can be found here.

The Common Imperial (Cheritra freja friggia)

A Common Imperial puddling at a sandy streambank

The next long-tailed species featured has a wider distribution than the Branded Imperial. The Common Imperial, although a moderately rare species, is more often encountered in urban parks and gardens than within the nature reserves. It can be skittish, and prefers to stay at higher levels at the treetops unless it comes down to feed or lay eggs.

The tails of the Common Imperial are generally longer than those of the Branded Imperial, regularly exceeding 10mm when measured from the tornal area of the hindwing. The male Common Imperial is a deep midnight blue above, whilst the female is brown. The underside is mainly white, with the apical area of the forewing shaded a pale orange. The tornal spots on the hindwing are overlaid with metallic blue-green scaling.

Similar to the Branded Imperial, this species has three tails originating from veins 1a, 2 and 3 of the hindwing, of which the longest is at vein 2. The long, thick white tails have a dark line in the middle, and the ends are often soft and "actively" twirling in the breeze when the butterfly stops to rest. The caterpillar of the Common Imperial feeds on a number of host plants, and the full life history can be found here.

The Fluffy Tit (Zeltus amasa maximinianus)

The third of the long-tailed species featured in this week's article is the moderately common Fluffy Tit. It can be found in urban parks and gardens, as well as in our forested nature reserves. It is usually encountered singly, flitting amongst the shrubbery with its long tails prominently seen trailing behind it as it flies rapidly from leaf to leaf.

A puddling Fluffy Tit

The male of this species is black above, with the basal area of the forewing and a large part of the hindwing coloured a pale azure blue. The female is a dull brown above. The underside is predominantly white, with dark orange areas at the apical areas of both the fore- and hindwings. The hindwing has a prominent black spot at space 2. The hindwing features only two pairs of tails, originating from veins 1b and 2. The longer tail at vein 2 is often twirled in a spiral and appear "softer" throughout its length when compared with the other two species featured in this article.

Male Fluffy Tits are regularly encountered puddling at damp footpaths and stream banks in the nature reserves. It is also sometimes seen feeding on bird droppings. The species is also regularly photographed, feeding on the flowers of the Bandicoot Berry (Leea indica). The life history of the Fluffy Tit has also been recorded and the details can be found here.

And so we are acquainted with 3 of these long-tailed hairstreaks that call Singapore home. In the 2nd part, we will meet 4 other long-tailed species, and one of which features the longest tails amongst all the species in the Theclinae sub-family in Singapore.

Text by Khew SK : Photos by Sunny Chir, Chng CK, Antonio Giudici, Goh LC, Khew SK, Loke PF, Bobby Mun and Anthony Wong

Life History of the Common Tiger

Life History of the Common Tiger (Danaus genutia genutia)

Butterfly Biodata:
Genus: Danaus Kluk, 1802
Species: genutia Cramer, 1779
Subspecies: genutia Cramer, 1779
Wingspan of Adult Butterfly: 70-80mm
Caterpillar Local Host Plants: Cynanchum ovalifolium (Apocynaceae), Cynanchum tunicatum (Apocynaceae).

Common Tiger form genutia.

Physical Description of Adult Butterfly:

On the upperside, the forewings are orange with a series of white spots in a broad, black apical border. The hindwings are either orange in form genutia or white with border tinged with orange in form intermedius. All veins on both fore- and hindwings are broadly marked with black. Marginal and submarginal series of small white spots are embedded in a black border at terminal margins of both wings. On the underside, the wings are similarly marked as per the upperside but with apical border orangey brown on the forewing

Common Tiger form intermedius.

Common Tiger form intermedius.

Common Tiger form genutia.

Field Observations of Butterfly Behaviour:

Both forms of the Common Tiger can be found in Singapore with form genutia being the more common of the two. This species is typically found in urban or sub-urban areas where its host plants are available. The adults typically visits flowers and has a fondness for sap exuded by Crotalaria spp.

Early Stages:
Locally, caterpillars of Common Tiger have been found to feed on leaves of two host plants in Apocynaceae: Cynanchum ovalifolium and Cynanchum tunicatum. Elsewhere in the region, Raphistemma spp. (Apocynaceae) have also been recorded as larval hosts in Malaysia and Thailand.

Local host plant #1: Cynanchum ovalifolium.

Local host plant #1: Cynanchum tunicatum.

The eggs of the Common Tiger are laid singly on the leaf of the host plant, typically on the underside. The milky white egg is shaped somewhat like a truncated rugby ball (diameter: 0.9mm, height: 1.3mm). The egg surface is ribbed with ridges running longitudinally. The micropyle sits atop.

A mating pair of Common Tiger.

A mother Common Tiger ovipositing on the young shoot of its host plant.

An egg of the Common Tiger, height: 1.3mm.

The egg takes about 3 days to hatch. The young caterpillar emerges by eating away part of the egg shell. The rest of the egg shell becomes the first meal for the newly hatched, which has a length of about 2.6mm. Its whitish body has a fair number of short, black setae. The large head capsule is black in color and there is a small black patch at the posterior end. A pair of short sub-dorsal protuberances can be found on each of the following four segments: 1st and 2nd thoracic segments, 2nd and 8th abdominal segments. Of these, the prothoracic pair is black in color and the remaining pairs greyish. The thoracic legs are black in color.

Two views of a newly hatched caterpillar, eating its egg shell, length: 2.6mm.

Once the newly hatched moves on to feed on leaf lamina over the next few hours, its body starts to take on a green undertone. The growth is rather rapid with the body length doubling to about 4.8mm next day, and after just 1.5 days from hatching, it moults to the 2nd instar. Towards the second half of the 1st instar, the last three pairs of protuberances turn reddish brown and pairs of oval-shaped yellow spots, flanked by smaller reddish brown spots, appear on the dorsum from the 2nd thoracic segment to the 8th abdominal segment.

Two views of a 1st instar caterpillar, length: 4.2mm.

Two views of a late 1st instar caterpillar, dormant prior to its moult, length:4.8mm.

The body of the 2nd instar caterpillar is whitish in ground color. One obvious change is the lengthening of those black protuberances on the 2nd thoracic segment, 2nd and 8th abdominal segments. The pair of protuberances on the 1st thoracic segment remains subdued in size. A yellow band, interrupted by reddish brown spots, runs sub-spiracularly. The dorsal pairs of yellow spots are flanked by dark reddish brown spots which extend laterally to the subspiracular yellow band. The black head capsule now has a triangular white patch on the frons and two white arches. This instar lasts about 1 day with the body length reaching 7.6-8mm before the moult to the 3rd instar.

Two views of a newly moulted 2nd instar caterpillar.

Two views of a 2nd instar caterpillar, length: 7mm.

Two views of a late 2nd instar caterpillar, dormant prior to its moult, length: 7.6mm.

The 3rd instar caterpillar is similar in appearance to the 2nd instar caterpillar, One obvious change is in the three pairs of processes which are proportionately longer. This instar takes about 1.5 days to complete with body length reaching about 12mm.

Two views of a 3rd instar caterpillar, newly moulted, length: 7.5mm

Two views of a 3rd instar caterpillar, length: 10.4mm.

Two views of a late 3rd instar caterpillar, dormant prior to its moult, length: 11.6mm.

Retaining very much the same body features from the previous instar, the 4th instar caterpillar distinguishes itself in having proportionately longer processes, with the mesothoracic pair the longest and having a strong tendency to flex forward. The base of the first two pairs of processes exhibits a hint of red at this stage. This instar lasts about 1.5 days with the body length reaching about 22mm.

Two views of a 4th instar caterpillar, early in this stage, length: 13.5mm.

Two views of a 4th instar caterpillar, length: 20.8mm.

Two views of a late 4th instar caterpillar, dormant prior to its moult, length: 21.8mmmm.

The 5th and final instar caterpillar appears similar to the previous two instars except that all six processes now have a prominent crimson coloration at the basal portion. The sub-spiracular yellow band is broader and more prominent than in the earlier instars.

Two views of a newly moulted 5th instar caterpillar.

Two views of a 5th instar caterpillar, length: 34mm.

Two views of a 5th instar caterpillar, late in this stage, length: 38.5mm.

The 5th instar lasts about 2.5 days, and the body length reaches up to 39-41mm. On the last day, the caterpillar ceases feeding, and its body becomes shortened and decolorized. It wanders around in search of a pupation site. Typically it comes to a halt at a spot on the underside of a leaf, where the caterpillar spins a silk pad from which it soon hangs vertically to take on the pre-pupatory pose.

A pre-pupatory larva of the Common Tiger.

Pupation takes place about 0.5 days after the caterpillar assumes the hanging posture. The barrel-shaped pupa suspends itself from the silk pad with no supporting silk girdle. The greenish pupa has a median transverse series of connected silvery spots and a series of black dashes at the lower boundary of this transverse band. Length of pupa: 19-21mm.

Three views of a pupa of the Common Tiger.

Three views of a mature pupa of the Common Tiger.

After about 5 days of development, the pupal skin turns translucent as the development within the pupal case comes to an end. The prominent white spots and orange patches on the forewing upperside also become discernible. The following day, the adult butterfly emerges from the pupal case.

The eclosion event of a Common Tiger butterfly.

A newly eclosed Common Tiger clinging onto its pupal case.

References:

• [C&P4] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society, 1992.
• Butterflies of Thailand, Pisuth Ek-Amnuay, 2nd Edition, 2012
• A Field Guide to the Butterflies of Singapore, Khew S.K., Ink On Paper Communications, 2nd Edition, 2015.

Text by Horace Tan, Photos by James Chia, Bob Cheong, Mark wong, Anthony Wong, Simon Sng, Sunny Chir and Horace Tan