22 November 2020

Favourite Nectaring Plants #18

Butterflies' Favourite Nectaring Plants #18
The Blood Flower (Asclepias curassavica)

An orange-hindwinged form-chrysippus Plain Tiger feeding on the flowers of the Blood Flower

Our 18th feature plant in the series of butterflies' favourite nectaring plants is a non-native "milkweed" that comes from tropical South America. This plant is better known locally in Singapore as one of two of the caterpillar host plants of the Plain Tiger (Danaus chrysippus chrysippus). The Blood Flower (or Scarlet Milkweed) is sometimes cultivated in butterfly gardens to attract and support the conservation of the Plain Tiger.

A white-hindwinged form-alcippoides Plain Tiger feeding on the flowers of the Blood Flower

The Blood Flower is a lactiferous plant from the dogbane family, Apocynaceae. When parts of the leaves or stems are snapped or damaged, a whitish milky fluid is excreted. This milky sap is poisonous and can cause skin irritation in sensitive people. The caterpillar of the Plain Tiger sequester the toxic constituents of the plant to make it distasteful to predators like birds. The adult butterfly is also distasteful, as are the other species in the Danainae sub-family, and displays aposematic colouration.

A lush patch of Blood Flower with healthy blooms
The Blood Flower is also known by several common names, one of which is "Scarlet Milkweed".  This is a sign at the Blood Flower patch at Gardens by the Bay

The plant is an evergreen erect herbaceous perennial, and grows up to 1.2m tall. It is usually cultivated for its attractive red and orange flowers.  There are also all-yellow flowered cultivars. The plant has a small spread and is never considered bushy. It is best cultivated in plant beds and as feature plants in landscaped gardens. For a better visual effect, 20 or more plants should be planted together.

Young Blood Flower plants grown together in a butterfly garden patch

The Blood Flower is considered a low shrub and sometimes cultivated in pots too. It flowers throughout the year and usually does best in open areas in full sunshine. It is an exotic and it does not grow naturally in Singapore and where it grows, it has usually been cultivated. Its region of origin is Tropical South America. Its presence in Singapore is limited to cultivated parks and gardens, usually grown as an accent shrub for its colourful flowers in combination with other flowering plants.

A Plain Tiger caterpillar munching on the flower of the Blood Flower

Plant Biodata:
Family: Apocynaceae
Genus : Asclepias
Species : curassavica
Synonyms : Asclepias bicolor, Asclepias margaritacea, Asclepias aurantiaca, Asclepias curassavica var. concolor, Asclepias cubensisAsclepias nivea var. curassavica
Country/Region of Origin : Central and Northern parts of South America, Mexico, Curacao
English Common Names : Blood Flower, Cancerillo, Sunset Flower, Pleurisy Root, Cotton Bush, Red-head, Indian Root, Swallow Wort, Scarlet Milkweed, Matal, Bastard Pecacuanha, Milkweed, Silkweed, Mexican Butterfly Weed
Other Local Names : Kakatundi, Madhar (Hindi),马利筋, 连生桂子花

Some butterflies love the attractive red and orange-yellow flowers of the Blood Flower

As a tropical plant, the Blood Flower blooms continuously throughout the year. It is relatively heat tolerant and and grows best in full sun with regular moisture. As the plant flowers and grows older, it is likely to look lanky and unattractive. It is then time to cut it down and let it sprout new shoots to regenerate growth again. The plant is susceptible to sucking insects like aphids and mealy bugs and is often attacked by these pests, particularly on the young shoots and growth of the plant, stunting its growth and turning the leaves yellow.

The green lanceolate leaves of the Blood Flower plant

The leaves of the Blood Flower are simple, opposite, shortly petioled, lanceolate to narrow-elliptic in shape, acuminate and measure 6 to 15 cm long and 6 to 25 cm wide. The base is narrowed. The leaves are green, sometimes with a white mid-rib. The stems are smooth, round and dull green permeated with red when young, turning to brownish-grey when matured.

Buds of the Blood Flower.  Note the aphids feeding on the stems
A close up shot of the flower of the Blood Flower
Flowers of the Blood Flower plant in various stages of maturity
The all-yellow flowers of a rarer cultivar of the Blood Flower

The flowers are perfect, radially symmetrical or irregularly shaped, bright red or orange with yellow centres, and measure approximately 12.5 mm. There are five sepals, deeply divided, reflexed and green. There are five petals which are linear with base united into a fused corolla. The corolla lobes are red, reflexed, oblong and approximately 8 mm long. The corona is hood-shaped with inwardly curved horns. There are five stamens. Anthers have two pollen sacs. The style filaments are united with pistils which have two carpels.

A young follicle (seed pod) of the Blood Flower (left) ; and the ripened pod with the Blood Flower seeds all ready to be disperse by the wind

The fruit is a pair of dry dehiscent, spindle-shaped follicles, measuring 5 to 15 cm long. Seed pods are light green and elongated, with approximately 70 to 80 seeds and split lengthways on one side upon maturity. Seeds are ovate and flattened, brown, 6 to 7 mm long, and have a narrow wing completely encircling the margin. Each seed is topped with a coma comprised of silky white hairs, 2 to 3 cm long, that assist in dispersal by wind.

Two forms of the Plain Tiger 

The Blood Flower has medicinal uses. The roots are known as pleurisy root and used as an expectorant for pleurisy, pneumonia, and other lung problems. An extract of the roots has emetic and laxative effect. A poultice of the root is employed to treat ringworm and to stop bleeding. The milky sap of the stems is used to treat warts and skin parasites. A decoction of the plant is used to induce abortion.

A Common Mime feeding on the flower of the Blood Flower

Where the Blood Flower is cultivated, some of the common urban butterflies visit the flowers for its nectar. Amongst the Papilionidae, I have only seen the Common Mime (Papilio clytia clytia) feeding at its flowers. Perhaps the other Swallowtails and Birdwings prefer other nectaring sources than the Blood Flower, but it is also possible that the Common Mime, being a mimic of the Blue and Dark Glassy Tigers, is able to fool predators into avoiding it whilst feeding on this flowering plant with its more distasteful friends.

Tigers Galore!  Various Tigers enjoying the nectar from the flowers of the Blood Flower

The Danainae are often seen on the Blood Flower as a nectaring source, and we have recorded the Common Tiger, Plain Tiger, Black Veined Tiger, Blue Glassy Tiger and Dark Glassy Tiger feeding at the flowers of this plant. Further observations are needed to see if other species of the Danainae also feed on this nectaring plant.

Various Pieridae species feeding on the flowers of the Blood Flower

The urban Pieridae species like the Striped Albatross, Painted Jezebel, Mottled Emigrant and Lemon Emigrant have been photographed feeding on the flowers of the Blood Flower. This plant appears to be a alternative source of nectar for these species of butterflies, although they prefer to feed on other of their preferred flowering plants whenever those are available.

Three Pansies and a Tawny Coster on the flowers of the Blood Flower

Amongst the Nymphalidae, we have observed the Blue, Peacock and Chocolate Pansies using the Blood Flower as a nectaring source. The non-native Tawny Coster is also another regular visitor to this flower.

A female Plain Tiger ovipositing on the leaf of a Blood Flower

Besides being one of the caterpillar host plants of the Plain Tiger, the flowers of the Blood Flower are also a nectaring source for urban butterflies. This plant should be in the landscaping palette of a butterfly garden's designer, as it is certainly a butterfly-attracting plant that is visually attractive and easy to cultivate.

Text by Khew SK : Photos by Sunny Chir, Khew SK, Loh MY and Loke PF.

15 November 2020

Butterfly of the Month - November 2020

Butterfly of the Month - November 2020
The Common Line Blue (Prosotas nora superdates)

A Common Line Blue feeding at the flower of the Spanish Needle (Bidens alba)

It is the 11th month of a tumultuous 2020 and many of us would just wish that we could wake up in 2021 and all the nightmares of this year will be over! But if only the pandemic that has spread across the whole world will be so easy to get rid of. News of a viable and safe vaccine are already making their rounds and we can only wait with baited breath that there is light at the end of this dark tunnel that we have been crawling through for most of this year.

Over on the other side of the globe, the US Presidential Election is over. Or is it? Although the official results show that the US now has a new 46th President, there are still some quarters that harbour a different view that the incumbent still has a whisker of a chance to wrest the Presidency back. Whilst the rest of the world get down to the business of making our nations safe again, and to kick start the ailing economies, it should be a matter of time before we see a new President in the White House.

Back home on our Little Red Dot, the Covid-19 situation appears to be under control, with daily single digit or no new community infections for the past couple of weeks. Whilst there are still the irritating imported cases almost every day, the anticipation of a "new normal" or a semblance of getting our lives back, grows by the day. There is talk of a "Phase 3" on the cards, but it comes with a warning of a second wave, if we let our guard down. But looking around us in Singapore, it would appear that we are beginning to see a bit of pre-Covid normalcy, albeit with face masks as a default as we go about doing our daily business.

Our feature butterfly of the month of November 2020 is the small and inconspicuous Common Line Blue (Prosotas nora superdates). With a wingspan of only about 20-25mm, the Common Line Blue is a small species that is not easy to spot. It can hardly be considered "common", although it is quite widespread in distribution across habitats like urban parks and gardens. It can also be found in the forested nature reserves. Due to its diminutive size and erratic flight, it is not easy to identify the species when it is on the wing.

A mating pair of Common Line Blue : Left - Male, Right - Female

The male Common Line Blue is bluish-purple on its uppersides, with a very thin and almost imperceptible border. The upperside of the female is dark brown and mostly unmarked. The underside is ochreous in the male, and sometimes appears almost like a small orange butterfly, whilst the female is greyish buff with ochreous speckles.

There is a prominent tornal orange-crowned black eyespot edged with pale green iridescent scales on the underside of the hindwing. There is a long white tipped filamentous tail at vein 2 of the hindwing. The large eyes of the Prosotas species are jet black, whilst the thorax, palpi and the dorsal margin of the hindwing are covered with hairs, giving the butterfly a particularly shaggy and unshaven look.

The Common Line Blues are most often seen puddling at damp footpaths and sandy streambanks

The Common Line Blue has a weak but erratic flight, and often seen flying restlessly at low levels amongst shrubbery. At times, the butterflies are seen feeding at flowering plants, but males are most often spotted puddling at damp footpaths and sandy streambanks that are contaminated with animal excretions and other organic matter. Females are much rarer.

When stopped at rest, the species usually perches on the tops of leaves and twigs with their wings folded upright. At times during hot sunny days, male Common Line Blues are occasionally observed to sunbath with their wings almost fully open, to reveal their purplish-blue uppersides.

The Common Line Blue's life history has been recorded on two host plants in Singapore - Entada spiralis and the non-native Australian Wattle (Acacia auriculiformis).

Text by Khew SK : Photos by Janice Ang, David Chan, Chng CK, Goh EC, Khew SK, Koh CH and Horace Tan

08 November 2020

Flying Tigers 3.0

Flying Tigers 3.0
Featuring Singapore's Tiger Butterflies

And we're back again... Over twelve years ago, in Jan 2008, when we featured the different "Flying Tiger" species in Singapore, we had only five species of these Tigers recorded then. After many years of continued observations by butterfly enthusiasts in Singapore, the list of "Tigers" was updated to include more recent sightings of other species that were either vagrants, strays or seasonal migrants to Singapore. Back in that 2019 update, we featured 8 species (but inadvertently missed out one! Oops!)

So in this latest refresh, we add in the latest Tiger spotted at Butterfly Hill on Pulau Ubin recently - the Swamp Tiger (Danaus affinis malayana), and to correct the one we left out in the Flying Tigers 2.0 update : the Yellow Glassy Tiger (Parantica aspasia aspasia). Hence we now currently have 10 Flying Tigers spotted in Singapore as at 2020.

One of our extinct "Tigers" in Singapore, the Chocolate Tiger (Danaus melaneus sinopion) which has not been seen here in over a century!

One of the Tigers recorded by the early authors but has since gone extinct in Singapore is the Chocolate Tiger (Danaus melaneus sinopion). According to references, it has not been seen in Singapore since the 1900's. Nevertheless, it was listed as an extant species on the Singapore Checklist but its status is classified as extinct. However, it was even featured on an TransitLink stored-value ticket some years back, even though no one has actually seen the species in the wild in the past century.

A white-hindwinged form-intermedius Common Tiger feeding on the flowers of the Red Tree Bush (Leea rubra)
An orange-hindwinged form-genutia Common Tiger on the seed pod of the Rattlebox Plant (Crotalaria retusa)
A white-hindwinged form-alcippoides Plain Tiger feeding on the yellow flowers of the Blood Flower (Asclepias curassavica)
A two-in-one shot of a male orange-hindwinged form-chrysippus courting a feeding female white-hindwinged form-alcippoides.  Note the male's hair pencils extruded to spray pheremones to attract the female
A mating pair of Black Veined Tigers

The first group of Tigers under the genus Danaus features the more colourful species with colours that are reminiscent of their feline mammalian namesake - black and orange. Of the species found here in Singapore, the Common Tiger (Danaus genutia genutia), Plain Tiger (Danaus chrysippus chrysippus) and the Black Veined Tiger (Danaus melanippus hegesippus) are relatively common and can be sometimes found in numbers where their respective host plants and other Danainae-attracting plants are grown.

The latest addition to the Flying Tigers in Singapore - the Swamp Tiger (Danaus affinis malayanus)

The fourth and most recent species, the Swamp Tiger (Danaus affinis malayanus) was recently spotted on Pulau Ubin in Aug 2020. A single female individual was feeding at the flowers of the Bandicoot Berry (Leea indica) and stopped to rest at some vines. The species is known to prefer mangrove habitats in Malaysia, and was probably a stray from the mangroves of nearby Johor.  Pulau Ubin also has its patches of healthy mangroves and it is possible that the Swamp Tiger was looking for its host plant in the habitat.
A Dark Glassy Tiger feeding on the flower of the Spanish Needle (Bidens alba)
The seasonal Yellow Glassy Tiger feeding on the flower of the White Weed (Ageratum conyzoides)

The next genus of species of Tigers would be the Parantica, which features two species - the Dark Glassy Tiger (Parantica agleoides agleoides) and the seasonal Yellow Glassy Tiger (Parantica aspasia aspasia). The Dark Glassy Tiger is common in urban parks and gardens where the Rattlebox Plant (Crotalaria retusa) is cultivated. The Yellow Glassy Tiger, on the other hand, is a very rare vagrant that has only been seen in Singapore a handful of times in the field over the past 3 decades (although it is not uncommon in Malaysia).

A Blue Glassy Tiger feeding on the flower of the Golden Dewdrop (Duranta erecta)
A Grey Glassy Tiger perched on a palm frond. Note the much paler markings and the almost white hindwing cell

The genus Ideopsis hosts two species of Tigers that have been seen in Singapore. The first one, Blue Glassy Tiger (Ideopsis vulgaris macrina) is common and can be seen in various habitats and widely distributed all over Singapore. The more recently discovered Grey Glassy Tiger (Ideopsis juventa sita) is a rare vagrant that has only been seen twice so far - on Pulau Ubin and at the Singapore Botanic Gardens. This species is not rare in the coastal areas of Johor, and could have strayed over to Singapore on favourable winds.

A Dark Blue Tiger feeding on the flower of the Spanish Needle at Pasir Ris Park Butterfly Garden
A Blue Tiger puddling at a rocky outcrop

The final two Tigers are recent additions from the genus Tirumala. In the early records, there were no observations of any species of this genus in Singapore. It was only in the past decade that two species from this genus were spotted in Singapore. The Dark Blue Tiger (Tirumala septentrionis septentrionis) has been observed a handful of times in Singapore and the individuals were believed to be vagrants coming in from Malaysia. The Blue Tiger (Tirumala limniace) of which only a single sighting was made so far, was probably a stray or a stowaway that made its way to Singapore.

We have updated the list of Flying Tigers in Singapore to 10 this year, but will we ever see the remaining 5 that fly in Malaysia - a few of them montane or found only in the northern part of the peninsula? Who knows? With Mother Nature, there will always be surprises.

Text by Khew SK : Photos by David Chan, Khew SK, Loh MY, Loke PF and Mei Hwang