24 November 2019

Relative Abundance Indicators

Butterflies : Relative Abundance Indicators
From Common to Rare

A Malay Lacewing feeding on the flower of Lantana camara at Central Catchment Area. Circa 2005

A friend recently asked me, "so has your butterfly survey project concluded?". My answer was yes and no. Firstly, surveys to "inventorise" our local butterfly fauna are always "ongoing". Although each official project may last 1-2 years, like the Bukit Timah Nature Reserve Comprehensive Biodiversity Survey, and the current Pulau Ubin Biodiversity Survey commissioned by the National Parks Board, many local butterfly watchers and enthusiasts continue to observe and keep records of butterfly activity in Singapore.

A Magpie Crow feeding on a sweaty backpack strap at MacRitchie Nature Trail. Circa 2005

With social media and digital photography, it is much easier to collect records and collate information on butterflies today. Apps such as Biome and iNaturalist are relatively good repositories of sightings and documentation of species diversity, abundance and location. Data collected can henceforth be analysed and may give a better overview of butterfly activity across Singapore the years.

In the Red Data Book, the convention used to describe the relative abundance of species is crafted after the International Union for Conservation of Nature (IUCN) guidelines. The Red List Categories and Criteria were basically categorised by "threat to extinction". For the layman, it may be rather scientific and hard to relate to.

Hence, when I was working on the Butterflies of Singapore, I adopted a less scientific approach  and used a more simple "Relative Abundance Indicator" table and layman-friendly 6-category abundance indicators from "Common to Very Rare". The final category of "Seasonal Migrant" covers all the occasional appearances of species that are non-resident in Singapore.

The annual variability and irregularity in the sightings of certain species over the years continue to affect their relative abundance. It is more pronounced in some species compared to others. Hence what was listed as "common" or "moderately common" may be come "rare" and conversely, what was "rare" or "moderately rare" may become "common".

Examples of some of the more obvious species that may require a re-classification of their abundance, are highlighted here. These are certainly not exhaustive nor definitive and the relative abundance indicators will continue to evolve and change over the years, as more data and observations are collected.

1. The Magpie Crow (Euploea radamanthus radamanthus)

A Magpie Crow puddling at a damp streambank near Rifle Range Trail. Circa 2008

The Magpie Crow was widely distributed across Singapore in the past decade and often spotted mainly in the nature reserves. It was most regularly seen at the Bukit Timah Visitor Centre before the upgrading works, but has been spotted at Rifle Range Road Trail, Sime Forest, MacRitchie Reservoir Park, Upper Seletar Reservoir Park and many other localities.

A trio of Magpie Crows puddling at a muddy spot at Upper Seletar Reservoir Park in 2005

A Magpie Crow puddling on a concrete water pipe

Considered "Moderately Common" between 2005 and 2015, the Magpie Crow appears to be rarely sighted in recent years. Records from recent social media posts seem to validate this observation. Have there been any ecological changes that made the species become much rarer? Has its caterpillar host plant been affected in some way and become less common? We will need to keep looking out for this species again in the coming years to see whether its population rebounds.

2. The Malay Lacewing (Cethosia hypsea hysina)

The Malay Lacewing, once a regularly-seen species in the nature trails, appears to be much rarer these days

A favourite amongst butterfly watchers and photographers, the Malay Lacewing features intricate patterns on black and orange coloured wings and is one of the prettiest butterflies in Singapore. The species was also categorised as "Moderately Common" as it was often seen flying around in the Central Catchment Nature Reserves along forest trails and feeding on flowering plants.

A Malay Lacewing perched on a leaf at Ulu Sembawang Park Connector, Mandai. Circa 2013

Again, after 2015, records of sightings of this species have decreased significantly. The non-native Leopard Lacewing, discovered in 2005, was not known to aggressively compete with the Malay Lacewing for its host plant, Adenia macrophylla, as its caterpillars prefer to feed on Passiflora foetida found abundantly in urban areas. Could something have changed and the "invader" has edged the native species out? This is something for the environmental ecologists to study further.

3. The Common Tree Nymph (Idea stolli logani)

Will the Common Tree Nymph soar amongst the treetops as commonly as before?

The large and spectacular Danainae is always a crowd pleaser whenever it appears high up in the forest canopy, soaring and gliding amongst the treetops. It is a forest-dependent species and the Common Tree Nymph has almost exclusively been sighted only within the forested nature reserves of Singapore. Also categorised as "Moderately Common" between 2005 and 2015, sightings of this species have become rarer these days.

Three Common Tree Nymphs frolicking at tree-top level at Upper Seletar Reservoir Park in 2008

In the past decade, when the Spicate Eugenia is in full bloom, the flowers attract a myriad of butterflies.  The Common Tree Nymph is one of the species that makes an appearance.  In recent years, when this tree is in flower, the Common Tree Nymph is sadly absent.

At the forest fringes of the nature reserves, when the Spicate Eugenia (Syzygium zeylanicum) trees flower, there are many species of butterflies that are instantly attracted to feed on the nectar of the flowers. The Common Tree Nymph was one of the species that turns up regularly - sometimes even up to 3-4 individuals. In the past few years, when the Spicate Eugenia trees are in bloom, the Common Tree Nymphs have failed to show up. Has anything changed in the environment to make this species become "Rare"?

4. The Common Three Ring (Ypthima pandocus corticaria)

The Common Three Ring, the largest of the Ypthima species, is no longer as common as before

This "unattractive" butterfly was described in the reference book, Butterflies of the Malay Peninsula to "almost dispute the claim of the Common Grass Yellow to be regarded as the commonest butterfly in Malaya". Usually seen along forest fringes amongst grassy patches, this species was categorised as "Common". It flies close to the ground, and in the past, several individuals can be encountered at its favourite locations.

Today, the species is not as often encountered. Could it be due to the reduction of its grass host plant, Ischaemum muticum? For a common butterfly, its life history is interestingly long - between 30-35 days as a caterpillar. Did something happen in its habitats to interrupt the life history development? Once again, should the Common Three Ring, which was previously "Common" may now have to be reclassified as "Moderately Rare"?

The abundance of various species of butterflies will continue to change and evolve, as the environment, habitats and ecology changes over the years. Climate change may have a strong influence on these factors. Nature groups and researchers with the resources to undertake projects to sustain butterfly populations in Singapore may need to widen their scope to look at some of these previously "common" species and target species recovery programmes to include these butterflies.

Text and Photos by Khew SK

17 November 2019

Flight of the Imperials

Flight of the Imperials
Featuring Singapore's Imperial Butterflies

A Branded Imperial perches on a leaf in the shaded forest understorey

The English word "imperial" is usually used to refer to things or people that are or were connected with an empire or pertaining to an emperor or empress. When the early collectors coined the name Imperial for some species of the Lycaenidae family, it is highly likely that they were using the word to describe these majestic butterflies that awed them with their breath-taking colours and beauty.

A Green Imperial stops to rest on the flower of the Javanese Ixora

In the world of butterflies, the Imperials are pretty, colourful and usually long-tailed species belonging to the sub-family Theclinae of the Lycaenidae family. Singapore is home to five of these Imperials, all of which are forest-dependent and usually found only in the heavily forested nature reserves. Of the five, only one is considered common and regularly seen by nature enthusiasts.

A female Great Imperial feeding on the flower of the Javanese Ixora

This blogpost takes a look at these five Imperial butterflies found in Singapore. Interestingly, each one of the five belongs to a different genus. All have orange with white undersides and black tornal markings. Their long tails are remarkable features on these species, and two of them probably sport the longest tails amongst the extant butterflies in Singapore.

1. The Branded Imperial (Eooxylides tharis distanti)

A Branded Imperial shares the sweet sap of the Bandicoot Berry with some ants

The first of the Imperials is the Branded Imperial. This species is by far the commonest of the five species and is regularly found along forest paths in the shaded understorey of our nature reserves. At times, several individuals can be seen together, particularly when they are feeding on the young shoots of the Bandicoot Berry (Leea indica).

A male Branded Imperial opens its wings to sunbathe.  Note the prominent brands on its forewings

The wings are black above with blue-dusted tornal area on the hindwing. In the male, a prominent "brand" can be seen on the upperside of the forewing. This could be why the butterfly is named Branded Imperial. The underside is reddish-orange with the hindwing bearing black sub-marginal spots on the white tornal area. There are 3 tails on the hindwing, of which the one along vein 2 is the longest.

The species' caterpillar feeds on the invasive weed Smilax bracteata which it shares with another Lycaenid, the Yamfly. As this non-native weed is very widespread in the nature reserves (despite efforts to remove the weed), the Branded Imperial has become a common species in Singapore.

2. The Common Imperial (Cheritra freja friggia)

The Common Imperial is a moderately rare species but is quite widespread across the island. Although found in the forested nature reserves, it can sometimes be found in urban parks and forested ridges in Singapore. It is usually observed singly and prefers to stay at treetops. It has a habit of perching on favourite leaves and returns time and again to the same perches as it flies around.

A male Common Imperial sunbathing with its wings opened to show the purple-blue uppersides

The male Common Imperial has purple-blue forewings on the upperside, whilst the female is dark brown. There are large black spots on the tornal area of the hindwing. Te underside is mainly white, with part of the forewing and the apical area of the hindwing shaded a light orange. The tornal spots on the hindwing are overlaid with metallic blue-green scaling. It has 3 tails of which the one at vein 2 is the longest.

The species' caterpillars feed on two species of common roadside trees, the Wild Cinnamon and the Red Saga. It has also been bred on other forest plants that are mainly found in the nature reserves. The species is observed to sunbathe with open wings at certain hours of the day at sunlit spots.

3. The Green Imperial (Manto hypoleuca terana)

The Green Imperial is considered rare in Singapore. It is usually seen at the forest edges of the nature reserves, feeding on the nectar of flowering plants. It is a fast-flying species that probably prefers to stay at the treetops.

The male of the Green Imperial is a shining bluish-green above, with broad black apical area on the forewing. The underside is largely orange and unmarked on the forewing, whilst the hindwing has black sub-marginal spots and streaks. The female is dark blackish-brown above with the usual black spots on a white tornal area on the hindwing. The underside of the dorsal area of hindwing is white, whilst the other areas of the forewing and hindwing are orange. The species has 2 tails - a relatively long tail and vein 2 and a short stubby one at vein 3.

Female Green Imperial. Top : Underside Bottom : Upperside

The species is one of several rare Lycaenidae that feeds on the parasitic plant, Macrosolen cochinchinensis, that can be found growing on large trees and bushes all around the island. The females have been observed ovipositing on the leaves of the host plant in the early afternoon and lays her eggs on the young shoots of the plant.

4. The Great Imperial (Jacoona anasuja anasuja)

Another rare Imperial, the Great Imperial has been observed only in the forested nature reserves of Singapore. The adult butterfly appears to be another tree-top dweller but occasionally can be seen to descend to low level shrubbery to feed or oviposit. When disturbed, it can fly rapidly up the treetops.

Top : Female Great Imperial Bottom : Male Great Imperial

The male of the Great Imperial is a deep shining blue on the upperside with an oblique band running across the apical area of the forewing. The female is predominantly brown above with a white tornal area on the hindwing. The underside is mainly orange with the forewing apical area a darker shade. The dorsal area of the hindwing is white with the tornal black streaks and spots. Both sexes have tails, where the males have a shorter sword-like tail at vein 2 whilst the female's tail is much longer.

The caterpillar host plant of the Great Imperial is the common Malayan Mistletoe. However, the species is not usually found in urban parks and gardens. It is found along the forest fringes and where it is observed, it is perched on the uppersides of leaves with its wings folded upright. Both sexes also descend from the treetops to feed on flowering plants.

5. The Grand Imperial (Neocheritra amrita amrita)

The last of the Imperials is also a rare forest-dependent species that is quite local in distribution. Its caterpillar host plant is found in the nature reserves and is quite rare. The plant has yet to be positively identified. However, the Grand Imperial was seen in numbers on the military-training island of Pulau Tekong in the early 2000's during a period of biodiversity surveys. It is not known if they are currently still as common.

A male Grand Imperial feeding on flowers

The male Grand Imperial has a royal blue upperside, with the apical areas of both wings black bordered. The female is dark brown and largely unmarked, except at the white tornal area where there are black spots. The underside of the forewing and costal half of the hindwing is dark orange whilst the remaining part of the dorsal area of the hindwing is pure white.

A female Grand Imperial sunbathing

The Grand Imperial has the longest tails of any Lycaenidae found in Singapore. It has 3 tails, of which the longest tail is at vein 2, whilst there are two shorter tails at veins 1b and 3 of the hindwing. The male has a prominent raised 'disc' on the underside of the forewing.

Text by Khew SK : Photos by Huang CJ, Khew SK, Simon Sng, Jonathan Soong, Horace Tan and Tea Yi Kai

10 November 2019

Black and White

Black and White
Featuring some black and white butterflies

Butterflies are traditionally portrayed as pretty insects adorned in all colours of the spectrum, fluttering gracefully amongst flowers. Moths, on the other hand, are often depicted as drab ugly creatures that only fly at night. In nature, and amongst Lepidoptera, this may be furthest from the truth!

There are numerous colourful moths in our environment - some even more spectacularly coloured than butterflies. On the other hand, there are also many drab-coloured and relatively unattractive butterflies. The colour of a butterfly's wings are often the subject of attention and enthusiasts tend to assess a butterfly's "attractiveness" by the colour and pattern of its wings.

However, like all of Mother Nature's creations, there is always a great diversity in the appearance of our natural world. Butterflies are no exception. This blogpost takes a look at some species of butterflies whose wings do not feature any colour of the visible spectrum, but are predominantly black and white, both on the upperside and underside of their wings.

Almost all black and white, the Helens have red or blue ocelli adorning their hindwings

Amongst the Birdwings and Swallowtails in Singapore, there are some species that have primarily black wings with some white patches. However, many of these also feature red, blue and other coloured lunules/eyespots that would make them more 'colourful' than just appearing as black and white butterflies.

Amongst the Pieridae are some species that are mainly white in appearance, with their veins or wings featuring black borders and margins. Some of these species would qualify as black and white candidates in this article. The male Striped Albatross, the Cabbage White and the seasonal migrant, the Plain Puffin can all be considered black and white species in this family.

The Crows from the Danainae subfamily are predominantly black butterflies with white markings

The next group would be the Danainaes, of which the Crows in particular, feature a few species that are predominantly black, with some white spots and streaks on the wings. The Crows appear black as compared the Albatrosses in the preceding family that appear white. The noteworthy species are the Spotted Black Crow, Malayan Crow, King Crow, Blue Spotted Crow and Striped Black Crow that would qualify as black and white species.

The Tree Nymph species are large and slow flying black and white butterflies

Also amongst the Danainaes, are the Idea species or more popularly called the Tree Nymphs. These are large and spectacular black and white butterflies that are attractive in their own right, despite not have any other prominent colours on their wings, except for black and white.  The Common Tree Nymph and the Mangrove Tree Nymph are the black and white species that can be found in Singapore.

Only the uppersides of the Sailors and Sergeants are typically black and white.  Some of the species have orange, brown or bluish-grey undersides.

Some of the Sergeant and Sailor species of the subfamily Limetidinae are also black and white striped on their upperside of their wings. However, most of them have either orange, brown and bluish gray undersides which would make them black and white candidates only when viewed from their dorsal side.

The Chequered Lancer is one of the black and white species amongst the skippers but on the upperside, the wings have orange-brown spots

Most of the other species in the remaining subfamilies amongst the Nymphalidae, the Riodinidae and Hesperiidae are largely coloured and very few can be considered true black and white butterflies. Some of the skippers come close to be purely black and white, but either their upperside or underside are brownish or with coloured accents that do not make them true black and white butterflies.

The Polyommatinae species in the Lycaenidae family feature some true black and white butterflies

In the family Lycaenidae, three Singapore-extant species, the Elbowed Pierrot, Malayan and the Quaker can be considered black and white species as both their under and uppersides are predominantly of black and white or grayscale colouration in appearance.

With that short introduction to our black and white species found in Singapore, see if you can spot any more that may come over from neighbouring countries in future. These species are considered the "Zebras" of our butterfly world - just simple black and white like the mammalian namesake from the horse or Equidae family.

Text by Khew SK : Photos by Sunny Chir, Federick Ho, Khew SK, Koh CH, Loke PF, Jonathan Soong and Benjamin Yam