23 March 2019

Three Archdukes

Three Archdukes
Singapore's Archduke butterfly species

A male Archduke foraging amongst the leaf litter in the shaded forest understorey

In my earlier article on this blog, I postulated that the English common naming convention of butterflies could have been possibly coined after the titles of English peerage or Imperial gentry and military ranks. In this article, we take a look at the Archduke butterfly species that can be found in Singapore.

A female Dark Archduke on leaf litter 

Unlike the English peerage titles, the Archduke (feminine: Archduchess) was a title that originated from the Habsburg rulers of the Archduchy of Austria. It denotes a rank within the former Holy Roman Empire, which sat just below that of Emperor and King.

Hierarchy of titles in Imperial, royal, noble, gentry and chivalric ranks © Wikipedia

The etymology of the word Archduke originates from various European languages and purportedly signifies authority or primary (Arch) and leader (Duke). Notwithstanding the historical origins of the royalty-linked name, the Archduke butterflies are no less majestic in their size and prominence in the butterfly world, befitting of their common name.

A Yellow Archduke perches on a leaf in the forested nature reserves

There are 3 extant species of Archdukes that can be found in Singapore. Belonging to the genus Lexias, which features large, robust-bodied and fast-flying butterflies that prefer the heavily shaded forests rather than open sunny areas. All are considered forest-dependent and not found in urban parks and gardens. They are usually found foraging for over-ripened fruits and feeding amongst the leaf litter on forest paths.

The Archduke (Lexias pardalis dirteana)

Upperside and underside of a male Archduke

The commonest species of the genus, the Archduke displays sexual dimorphism in that the male is physically very different from the female. The male is dark velvety black above with a broad blue hindwing border, which is continued (usually in a lighter shade) along the termen of the forewing. The underside is a deep reddish brown with yellow spots.

Upperside and underside of a female Archduke

The female is dark brown above, with prominent yellow spots on both wings, including the body of the butterfly. The underside is a light brown with the yellow spots showing through. The hindwing is a pale-greyish blue throughout.

Note the bright orange apical tip of the Archdukes' antennae

In both sexes, the apical portion on the topside of the antennae is prominently orange. The orange colour is continued on the underside of the antennae as well. This is the most reliable distinguishing characteristic that separates the Archduke from its very closely related Dark Archduke.

The Dark Archduke (Lexias dirtea merguia)

A male Dark Archduke on leaf litter

Almost identical to the Archduke, the Dark Archduke (previously called the Dark-Tipped Archduke), is also sexually dimorphic, with the male and female's appearance corresponding to the Archduke. The habit of this species mirrors the Archduke, and individuals are often found feeding on rotting fruit and other organic matter amongst leaf litter on the forest floor.

Upperside and underside of a female Dark Archduke

The male and female of the Dark Archduke closely resemble the corresponding sexes of the Archduke. The male is velvety black above with the blue marginal border on the hindwing, which extends to the termen of the forewing. The female is dark brown with yellow spots on both wings.

Note the black antennal tips of the Dark Archduke male and female

The primary difference between the Archduke and Dark Archduke is that the apical portion of the antennal club is black instead of orange. The underside of the antennae can still show some orange colouration like the Archduke. It is almost impossible to distinguish the two species when in flight, although there are some key, but still variable differences on the wings of both species to help distinguish them.

The Yellow Archduke (Lexias canescens pardalina)

Yellow Archduke puddling on the forest floor

The third, and smallest species of the three Archdukes is the Yellow Archduke. Of great interest is that it is the only species in the Lexias genus that is not sexually dimorphic! Both the male and female look alike, although the female is usually much larger. Displaying the same forest-floor foraging habits as its two other cousins, it is also a forest-dependent species.

Upperside and underside of the Yellow Archduke

The Yellow Archduke is dark brown above with large yellow spots on both wings, resembling the females of the Archduke and Dark Archduke. However, both the males and females look alike. The underside of the hindwing only has the dorsal margin a pale-greyish blue with the larger part of the wing brown and yellow.

Mating pair of the Yellow Archduke

On the upperside of the forewing, the line of yellow spots at the post-basal area features a spot (the 4th spot from the base) which is coalesced into a single spot. In the female Archduke and Dark Archduke, this yellow spot is split into two spots. This is the most reliable characteristic to separate the Yellow Archduke from its two close cousins.

Text by Khew SK : Photos by Khew SK, Koh CH, Nelson Ong, Simon Sng and Jonathan Soong

17 March 2019

Assorted Nectaring Plants - Part 4

Butterflies' Nectaring Plants
Assorted Flowering Plants - Part 4

A Blue Glassy Tiger feeding on the flower of the Belimbing (Averrhoa belimbi)

We are back with a selection of another six flowering nectar plants that butterflies visit for their source of energy to go about their daily activities. These plants, on the other hand, have adapted their reproductive parts to suit their pollinators e.g. bees, butterflies, moths, etc., to ensure the continual survival of their species. As most people would know, in the process of feeding on the nectar from these flowers, butterflies help to pollinate the plant which enables fertilisation and the production of seeds for the next generation of the plant.

A Dark Glassy Tiger feeding on the yellow flower of the Pig's Grass (Synedrella nodiflora)

Butterfly-plant relationships are not limited to their caterpillars that feed on their specific host plants. Adult butterflies have a preference for different types of flowering plants for their nectar source. Whilst many butterflies have their preferred or favourite flowers, this series of assorted flowering plants showcases various other types of flowers that butterflies occasionally visit for their daily liquid diet.

19. Bougainvillea (Bougainvillea glabra) hybrids

Colourful bracts of the Bougainvillea makes it a popular landscaping plant.

This attractive flowering plant is almost synonymous with the urban landscape of Singapore - from the time a visitor arrives at Changi Airport and takes a drive down the tree-lined East Coast Expressway into town. The colourful bracts of the Bougainvillea comes in many colours from white and yellow to pink and red. They adorn roadside verges, overhead bridge planters and are commonly seen as a decorative plant in public and private gardens.

Despite its showy colourful bracts, the actual flowers from which butterflies extract nectar are small and insignificant. These flowers are creamy-white, tubular and inconspicuous. Although the plant is common all over Singapore, butterflies are rarely attracted to the flowers for nectar. Only occasionally are butterflies observed to feed on the flowers for nectar.

A Tree Flitter probes deep into the tubular flower of the Bougainvillea

I have observed urban species like the Painted Jezebel, a couple of Glassy Tigers and some Swallowtails visiting the flowers for a quick re-fuelling stop, but they do not stay for long, or flutter from flower to flower on the plant to feed, unlike many of the other favourite nectaring plants. In the nature reserves, the occasional Skipper (Hesperiidae) are encountered feeding on the Bougainvillea flower in the early morning hours.

20. Pig's Grass (Synedrella nodiflora)

A Suffused Flash feeding on the flower of the Pig's Grass

This herbaceous plant can grow up to about 1-2m high and can be found along roadsides and wastelands. It appears to be more common in the backmangrove areas like Sg Buloh Wetland Reserves and Pulau Ubin. The small yellow flowers can sometimes be mistaken for the more common creeper, the Singapore Daisy (Sphagneticola trilobata) which belongs to the same Asteraceae family as the Pig's Grass.

A Spotted Black Crow feeds in the yellow flower of the Pig's Grass

The yellow ray florets attract a number of Danainae like the Glassy Tigers and some of the Crows. At Sg Buloh, we have observed some Lycaenidae like the Suffused Flash and Singapore Four Line Blue feeding on the yellow flowers. The primary pollinator of this plant appears to be bees and wasps, and they are more often seen on the flowers than butterflies.

21. Malayan Eyebright (Legazpia polygonoides)

A Plain Lacewing feeding on the flower of the Malayan Eyebright

This slender herb is classified under the Torenia family, which comprises low ground creeping weeds that grow amongst the grass in open gardens and landscaped lawns. The leaves are small, rounded with toothed edges. The plant flowers frequently. The small flower has a lower white lip of three lobes, and upper lip of red. The centre is tinged with yellow.

The small unique flower of the Malayan Eyebright contains nectar which some butterflies feed on

The diminutive flowers usually attract the smaller butterflies in the Lycaenidae and Hesperiidae families, but the Grass Yellows and Tree Yellow have been observed to stop and feed on the flowers as well. It was a surprising observation when the rare and elusive Plain Lacewing (Cethosia methypsea methypsea) was photographed feeding on the flowers of the Malayan Eyebright in the early morning hours.

22. Belimbing (Averrhoa bilimbi)

A Blue Glassy Tiger feeding on the pretty red flower of the Belimbing

This medium-sized tree can grow from 5-10m tall. Originating from Southeast Asia, the Belimbing is known for its very sour fruits that are used as a relish or garnishing in local cuisine. It is also closely related to its more well-known cousin, the Starfruit (Averrhoa carambola). A unique feature of the Averrhoa plants is that they flower and fruit directly on their trunks and branches.

The flowers and fruits of the Belimbing growing off the branches of the tree

A Common Grass Yellow feeding on the flower of the Belimbing

The flowers are small purplish-red, borne in a pendulous panicle inflorescence. Each flower is 5-petaled and fragrant, and each inflorescence has about 60 flowers, usually growing off the trunk or branches of the tree. Occasionally, the flowers attract butterflies like the Glassy Tigers and Grass Yellows. I have not yet recorded any other species of butterflies feeding on the flowers.

23. Common Vernonia (Cyanthillium cinereum)

A Lesser Grass Blue feeding on the flower of the Common Vernonia

Previously known as Vernonia cinerea, this wild-growing weed usually found along roadside green verges, open wastelands and even cracks in the joints of paved concrete footpaths. It grows as a small herb and the stalks of the flowers grow upwards with several flower heads on a single stalk. The purplish to white flowers comprise fine disc florets to which small butterflies are attracted.

Various species of the Grass Blues like the flowers of the Common Vernonia as a nectaring source

Due to its very small size, this wildflower attracts the smaller Lycaenidae like the Lesser Grass Blue and the Pale Grass Blue. It is highly unlikely that any of the larger butterflies can feed on the Common Vernonia as it is 'designed' for only the very fine and small diameter proboscis of small butterflies that are able to feed on it.

24. False Heather (Cuphea hyssopifolia)

A Metallic Caerulean feeding on the flower of the False Heather

This low-growing shrub with fine leaves are often used in landscaping as a border plant to line footpaths or planters. The bright green leaves are opposite and pointed. A native of South America, the False Heather was probably introduced to Singapore as an ornamental plant used in cultivated landscaped gardens.

A Yellow Grass Dart feeding on the flower of the False Heather

The small purple flowers occasionally attract butterflies to feed on them when there is a shortage of other more popular nectar-laden flowering plants are not available. Amongst the species that have been observed to visit the flowers for nectar are Striped Albatross, the Grass Yellows, and other small Lycaenidae and Hesperiidae species.

Text by Khew SK : Photos by Chng CK and Khew SK

Assorted Nectaring Plants - Part 1
Assorted Nectaring Plants - Part 2
Assorted Nectaring Plants - Part 3

10 March 2019

Butterfly of the Month - March 2019

Butterfly of the Month - March 2019
The Common Four Ring (Ypthima huebneri)

A Common Four Ring perches on the tip of a leaf with its wings folded upright

The hot humid month of March is upon us, as temperatures seem to soar much higher than usual. The weather app on my iPhone appears to read above 32degC on most days for the past couple of weeks and the "feels like" temperatures can top 38degC around noon. The high Relative Humidity doesn't help much, as the short occasional showers just made it worse.

Our general landscape in the parks and gardens looks parched and dry and trails that we have walked in the nature reserves recently are crackling with dry leaf litter. The meteorological station's forecast predicts more hot weather in the coming weeks. During such months, water is more precious than usual, both for us humans and everything else in our natural world.

Speaking of water, it has been very much in the news of late, and our 'friendly' nonagenarian politician up north has been harping on an age-old issue of the price of water that Singapore buys from neighbouring Johor. Despite Singapore's efforts to be self-sufficient in its own supply of potable water via PUB's four national taps, one national tap - imported water from Malaysia, still makes up at least 20% of the daily demand.

A Common Four Ring opens its wings to sunbathe in the early morning hours of the day

Under a 1962 Water Agreement with Malaysia, Singapore is allowed to draw water from the Johor River and Linggiu Reservoir, with a provision that Singapore treats and provides 2% of this water back to Johor. The supply from this imported source is up to 250 million gallons of water per day up to 2061 - 51 years left to go.

The current dispute over the price of water is a thorny issue that continues to strain bilateral ties - depending on the politicians of the day. Only when Singapore completely eliminates this dependence on Malaysia for its water needs, will this off-again, on-again threats continue. It is only when our taps run dry, or when fresh clean water becomes unavailable, that we realise the importance of this critical natural resource that we normally take for granted.

A mating pair of the Common Four Ring

Our Butterfly of the Month for March 2019 is a small and usually under-appreciated Satyrinae, the Common Four Ring (Ypthima huebneri). The genus that this species belongs to comprises small, greyish-brown and streaked butterflies that frequent open grassy habitats at the forest edge. The English common name for the "Ring" butterflies refer to the number of rings on the hindwing of the various species.

The Common Four Ring is the smallest of the Ypthima species in Singapore. Rather local in distribution, the species is not considered very common except at the handful of habitats which it favours. It is a weak flyer and stays close to the ground in shaded grassy areas near the nature reserves. As its caterpillar feeds on the grass Ottochloa nodosa, it is usually found in the vicinity of its host plant. Where it occurs, usually several individuals are seen together.

The Common Four Ring has a greyish-brown undersides with fine striations on both wings. The forewing has a large yellow-ringed black ocelli with a pair of bluish dots within the black ocelli. The hindwing has four yellow-ringed black ocelli with a blue dot in each of the black ocelli. The arrangement, size and contiguity is very variable and the spectrum of diversity is discussed in an earlier article here.

Common Four Rings feeding on various flowers

Both males and females of the Common Four Ring are observed feeding on flowering plants in the forested areas, like Mile-A-Minute, Bandicoot Berry, Singapore Daisy and others. In the early morning hours, the butterfly can be seen fluttering around low shrubbery and grasses and then stopping to open its wings to sunbathe. As the day progresses and it gets warmer, the Common Four Ring tends to stop to rest with its wings folded upright.

It is also interesting that, for such a small butterfly that is moderately common, its total life history takes about 45-50 days from egg to eclosion - relatively long. The host plant, a common grass that grows easily along cleared forest edges, is also a host plant to at least five Hesperiidae, other Ypthima spp. and Mycalesis spp. So a common humble grass is important to these species of butterflies for their continued survival.

Text by Khew SK : Photos by David Chan, David Ho, Khew SK, Koh CH, Loh MY and Loke PF.