27 September 2020

The Disappearing Acts

The Disappearing Acts
Now You See Me, Now You Don't

A Plain Lacewing (Cethosia methypsea methypsea), one of the new discoveries recorded in the 1990's appeared and disappeared for many years before reappearing again, and has not been seen since 2016

Over the years, the number of species spotted and recorded in Singapore has continued to increase. Of these, some have become resident species after they have managed to sustain a viable population in Singapore. With adequate availability of host plants, these species have continued to breed and colonise their preferred habitats and some of these species, though considered non-native or exotic, have become a familiar sight in our local butterfly scene.

A Yellow Flat (Mooreana trichoneura trichoneura) that was first discovered at the NTU area in 2012 but individuals have continued to be spotted over the years

Some of these exotics that have been able to find a home in Singapore are species like the Tawny Coster (Acraea terpsicore), Leopard Lacewing (Cethosia cyane), Common Jay (Graphium doson evemonides), Pale Grass Blue (Zizeeria maha serica), Two Spotted Line Blue (Nacaduba biocellata), Orange Tailed Awl (Bibasis sena uniformis) and Yellow Flat (Mooreana trichoneura trichoneura), just to name a few of the over 35 new discoveries to Singapore. Of these, some have become common in the environment and are often encountered in urban parks and gardens, whilst others continue to be very rare.

The Orange Tailed Awl (Bibasis sena uniformis) a new discovery, continues to be spotted from time to time and its caterpillars were once "common" at the Singapore Botanic Gardens

However, there are some species that appear over a period of time, when several pristine individuals were seen for several weeks. Then for some mysterious reason, they disappeared altogether and not seen for many years. I am not referring to those species that are singly or randomly spotted, suggesting that they may be migrants, strays or vagrants from neighbouring countries. Or they could simply be very rare native individuals that are somehow surviving in Singapore's dense forested areas.

The Tawny Coster (Acraea terpsicore) and Leopard Lacewing (Cethosia cyane) are exotic visitors that are found relatively commonly in Singapore today

In this blogpost, we investigate three different butterflies - all non-native species, that have, for a short period, been spotted in very localised areas - even in numbers, but then after a few weeks or months, went completely missing and have not been seen for some time. What happened to these species? Perhaps their host plants were insufficient to sustain a population? Were they subject to genetic in-breeding that wiped out the population? Or was there some other reason to explain their disappearance? Will they re-appear again some time in the future?

1. The Malayan Jester (Symbrenthia hippoclus selangorana)

A pristine Malayan Jester (Symbrenthia hippoclus selangorana) sunbathes on a leaf at Dairy Farm Nature Park

The Malayan Jester was first recorded as a new discovery to Singapore in early 2012. Back then, an individual was first spotted in the western part of Singapore at the grounds of Nanyang Technological University. A subsequent individual was spotted a few days thereafter, and then there was no further sign of this species

Then, six years later, observations of this species were made over the period 2018-2019 at the Dairy Farm Nature Park. From the flurry of posts on social media, the Malayan Jester suddenly became "common" for a few months from around Oct 2018 to Jul 2019. It was seen quite regularly in the area and sometimes several individuals were spotted together. From the observations, quite a few of the butterflies photographed were pristine, suggesting that they had just eclosed recently, and could not have been migratory individuals (usually with worn out or tattered wings).

Then all of a sudden, the species disappeared altogether. Visits to the Dairy Farm area no longer yielded any sightings of this species. The Malayan Jester left town. As suddenly as it had appeared and became common, the species went missing again. Did something happen to the colony flying at Dairy Farm? Will it be back again anytime soon?

2. The Common Yeoman (Cirrochroa tyche rotundata)

A pristine male Common Yeoman sunbathes on a leaf at the Singapore Botanic Gardens

Some time in Jun 2015, a couple of sightings of the non-native Common Yeoman appeared. A species that is not rare in Malaysia, the Common Yeoman has not been recorded from Singapore before until those encounters in 2015. The bright orange coloured butterfly flies erratically and resembles the common Leopard found in our urban areas. This sighting was, interestingly, at the urban Singapore Botanic Gardens, and not in the forested areas where the species is more often found in Malaysia.

A tattered female Common Yeoman ovipositing on its caterpillar host plant at SBG

A few subsequent visits to the SBG showed that there was a small colony of this species breeding at a very localised area where its caterpillar host plant grows. All of a sudden, the species became "common" only in that area, and again, several individuals - both males and females, were found there. We even managed to document the full life history of the Common Yeoman from that encounter.

A female (top) and male (bottom) Common Yeoman spotted at the Singapore Botanic Gardens for a short period in 2015 and subsequently in 2018.  It has not been seen since. Is it still around?

It continued to be seen at SBG for about 3 months until Sep 2015, then vanished. Subsequent visits to that location were not fruitful, even though the host plants were still there and nothing has changed in the habitat. It was only about 3 years later, in Apr 2018 that another sighting was recorded at SBG again. But this time around, it did not stay long and it disappeared after that. It is not known for sure if this species continues to survive in Singapore. How do we help to conserve this species sustainably? What are the secrets that the butterfly need to tell us to help it continue to exist in Singapore?

3. The Plain Lacewing (Cethosia methypsea methypsea)

Butterfly watchers had to wait for 14 years for the return of the Plain Lacewing and in recent years, it has been missing again.

The Plain Lacewing was first recorded as a new taxon for Singapore some time back in early 1991. It was first observed at Upper Seletar Reservoir Park. Back then, I recalled that, whilst it was not common, it made regular appearances, feeding at the flowering plants in the reservoir park. The related and similar-looking Malay Lacewing was much more common. 

Over the next 10 years from 1991, there were few sightings of the Plain Lacewing in Singapore, where it continued to be a rarity in the forested nature reserves. Then, all of a sudden the Plain Lacewing disappeared altogether, and there were no further sightings of the species for many years. The Malay Lacewing was the only Lacewing (Cethosia) species extant in Singapore until the discovery of another species, the Leopard Lacewing in 2005. In the meantime, the Plain Lacewing continued to elude butterfly watchers in Singapore.

Then suddenly, in 2014, sightings of the Plain Lacewing were reported by members of the butterfly watching community! After a long absence of 14 years, it was back! Several individuals were spotted over a few weeks, and seen mainly at the Upper Seletar Reservoir Park's forested areas. During that time, we also had the fortune of being able to document the species' life history, before it disappeared. Our records showed another sighting in mid 2016, two years later, and then the sightings stopped altogether. Why did it reappear again after 14 years, only to disappear again? Where did it "hide" all this time? Will butterfly watchers have to wait another 14 years again before spotting a Plain Lacewing again in Singapore?

Text by Khew SK : Photos by Khew SK, Koh CH, Loke PF, Jonathan Soong and Horace Tan

20 September 2020

Butterfly of the Month - September 2020

Butterfly of the Month - September 2020
The Malay Staff Sergeant (Athyma reta moorei)

A typical male Malay Staff Sergeant with the twice-constricted forewing cell streak

The month of September 2020 is well into its second half, and this year, the first half of the month coincided with the Chinese Hungry Ghost Festival. In Chinese folk legend, the seventh lunar month is the Ghost Month. It is said that every year on the first day of the seventh lunar month, the Gates of Hell will be wide open and the ghosts will come out until the gates are closed on the 30th day of the month, which fell on the 16 Sep this year. So we are now into the 8th month of the Lunar Calendar, and looking forward to delicious moon cakes.

The COVID-19 situation in Singapore appears to be improving, with low double digit infection cases in the recent few days, and few or no cases at all in the community. This is a good sign that the pandemic is well under control, and Singaporeans from all walks of life look forward to further relaxation of the controls that were put in place to manage the spread of the virus. But all these controls have been at the expense of the economy - and a valid trade-off.  Even so, Singapore's estimated Gross Domestic Product (GDP) for the full year is expected to land somewhere between -6% to -7% - its worst economic contraction since its independence in 1965!

As the economy takes a severe beating, the spectre of increased unemployment, job losses and salary cuts loom over the horizon. There is little cheer in the atmosphere, as our island state braces itself for the stormy seas ahead. Even as the government rolls out various measures to ease the pain of businesses and individuals, such schemes are not sustainable in the long term, and various sectors are compelled to craft new strategies to adapt to the new norm and reinvent their businesses to stay afloat.

The race is on, for a vaccine to eliminate the never-ending outbreaks and recurrence of the virus. Optimistically such a vaccine is hoped to wipe out the COVID19's effect across the globe. The current estimate of infections globally has already passed 30.8M with over 958,000 fatalities due to the virus.  The numbers continue to climb every day, with the US, India and Brazil taking the top three spots for total infections. And the world continues to search for a solution to end one of the most deadly pandemics in modern history.

Our Butterfly of the Month for September 2020 is a species that has recently made the news in taxonomic circles. The female of the Malay Staff Sergeant (Athyma reta moorei) had eluded many taxonomists and butterfly experts all this time. The discovery that the species is actually sexually-dimorphic was only made this year, after years of careful research and life history documentation. It is now confirmed that there is unlikely to be a black-and-white female of the Malay Staff Sergeant, and that the female is orange and black all along.

A puddling male Malay Staff Sergeant

The Malay Staff Sergeant is considered a rare species in Singapore, and is a forest-dependent butterfly. It is usually spotted singly feeding on flowers or puddling on damp sandy footpaths or streambanks.  The ripened fruits of the Singapore Rhododendron is also a favourite with this species. Interestingly, in Singapore, the females are more often encountered than the males. 

The diagnostic feature of the Malay Staff Sergeant is the twice-constricted white cell streak on the upperside of the forewing.  This streak is also well separated from the triangular spot beyond. The white bands in the males show a slight bluish tint at certain angles, but not as prominently as those in the related male Colour Sergeant.

The female is now known to be orange and black, and the differences between the female Malay Staff Sergeant and the lookalike female Colour Sergeant form-neftina are depicted in the annotated photo shown here. The female Malay Staff Sergeant is regularly observed singly, usually feeding at flowering plants or on the ripened fruits of the Singapore Rhododendron (Melastoma malabathricum)

Newly eclosed male (left) and female (right) Malay Staff Sergeant

The caterpillar host plant where it has been successfully bred on in Singapore, is Glochidion zeylanicum. The complete life history is recorded here.

Text by Khew SK : Photos by Huang CJ, Khew SK and Horace Tan

13 September 2020

Mistletoes and Butterflies

Mistletoes and Butterflies
Ecological importance of Parasitic Plants

A female Banded Royal opens its wings to sunbathe. A recent addition to the number of butterfly species whose caterpillars feed on mistletoe

A parasitic plant is a plant that derives some or all of its nutritional requirement from another living plant. All parasitic plants have modified roots, called haustoria, which penetrate the host plant, connecting them to the conductive system – either the xylem, the phloem, or both. This provides them with the ability to extract water and nutrients from the host. Parasitic plants which derive water/nutrients from the hosts and are photosynthetic are known as "hemiparasites".

The large leaves of the Malayan Mistletoe are able to support the big numbers of the common urban species like the Painted Jezebel.

There are currently 10 known species of parasitic plants extant in Singapore. Quite a few of these species, commonly referred to as "mistletoes", can be seen attached to a variety of host plants - from shrubs to large trees all around Singapore. Mistletoes are believed to have medicinal properties and used in traditional medicine to cure a variety of ailments like cough, diabetes, hypertension, cancer and as a diuretic.

In the popular Asterix and Obelix comics, the druid Getafix adds mistletoe as a key ingredient in his magic potion 

In the popular comic series Asterix and Obelix, the mistletoe is a key ingredient in the magic potion that endows our two heroes with superhuman strength. The druid Getafix, who makes the concoction, is often depicted in the comics cutting mistletoe, hidden amongst the lush treetops with a golden sickle that preserves the magical properties of the mistletoe.

The hemiparasitic Chinese Mistletoe attached to the host

Parasitic plants are not the most welcomed plants amongst arborists, tree maintenance personnel and gardeners. This is because, by virtue of the parasitic nature of these plants, they anchor themselves to a host shrub or tree and extract nutrients from the host. In very severe infestations, the parasitic plants may stunt the growth of the host or even kill it. However, in most cases, a host can support these parasitic plants for decades without significant adverse effect on the host. Nevertheless, these under-appreciated and misunderstood parasitic plants are often pruned and removed from the host.

The shiny leaves of the Rusty Mistletoe are reddish brown when young, but turn a deep green when mature

What then, are the ecological functions of these "parasites" of other plants? Plants research has shown that mistletoes are keystone species in forests and woodlands. A keystone species is one which has a very significant influence in an ecosystem, and if removed may cause undesirable impact to the ecology. Many birds, insects and aboreal mammals build their nests among mistletoes. A wide variety of animals and insects feed on the leaves, shoots, fruits, flowers and nectar of mistletoes.

The Singapore Mistletoe Story by Francis Lim - a book about the parasitic plants in Singapore

Amongst the species of mistletoes in Singapore, three are of particular importance to butterflies. They are host plants to a variety of common to very rare species of butterflies. This article explores these species of mistletoes which are hosts to the caterpillars of these butterflies. It is also likely that the remaining 7 species of mistletoes may be caterpillar host plants for other species of butterflies, but this has yet to be discovered and hopefully recorded in time to come.

1. Malayan Mistletoe (Dendrophthoe pentandra)

The lush green leaves of the Malayan Mistletoe with flowers on its stem

The Malayan Mistletoe is by far the most common mistletoe in Singapore. It is a familiar site on roadside trees and in urban gardens, especially where plants are neglected or unkempt. It is quite often seen on plants like the Shui Mei (Wrightia religiosa) in private gardens, as well as any urban trees where birds spread the seeds of this parasitic plant, ranging from fruit trees like mango and chiku, to a wide variety of other roadside trees.

This common parasitic plant is a caterpillar host plant to at least five different species of butterflies across three families. These are :
  1. Painted Jezebel (Delias hyparete metarete)
  2. Green Baron (Euthalia adonia pinwilli)
  3. (Tajuria dominus dominus)
  4. Peacock Royal (Tajuria cippus maxentius)
  5. Great Imperial (Jacoona anasuja anasuja)

The distasteful Painted Jezebel's caterpillars have somehow managed to sequester the chemicals from the Malayan Mistletoe to make itself unattractive to predators

Amongst these species, it is interesting to note that the aposematic Painted Jezebel is believed to be distasteful to birds and has somehow managed to sequester the chemicals in the Malayan Mistletoe as a protection against predators. This is something that the other 3 species that feed on the same host plant are not able to do so, or at least the adult butterflies are not known to be distasteful to predators.

The flowers of the Malayan Mistletoe

The Malayan Mistletoe is most likely dispersed mainly by the birds that feed on its fruits, and then transporting the seeds to other trees where the bird droppings, which contain the seeds, are deposited on the branches of other plants. As the seeds ripen, it will extend its haustoria (specialised roots) and penetrate into the host as it takes grip and grows. The haustoria of the Malayan Mistletoe tends to grow into a ball-like form as the plant matures.

2. Chinese Mistletoe (Macrosolen cochinchinensis)

A healthy growth of the Chinese Mistletoe

The next most common species of our local parasitic plants, is the Chinese Mistletoe, which, like the previous mistletoe, is also a stem hemiparasite. It attaches itself to the branches of its host and grows into a large bush that can span 1m-2m across. Depending on the size of the host, the growth of the Chinese Mistletoe can sometimes overwhelm and smother the entire host.

The Chinese Mistletoe is a caterpillar host plant to an even wider variety of butterfly species (some of which also feeds on the Malayan Mistletoe). These are :
  1. Green Baron (Euthalia adonia pinwilli)
  2. Centaur Oakblue (Arhopala centaurus nakula)
  3. Peacock Royal (Tajuria cippus maxentius)
  4. Banded Royal (Rachana jalindra burbona)
  5. Felder's Royal (Tajuria mantra mantra)
  6. Green Imperial (Manto hypoleuca terana)
  7. Great Imperial (Jacoona anasuja anasuja)
  8. Semanga superba deliciosa.

The flowers and fruits of the Chinese Mistletoe, on which the caterpillars of the Green Imperial and Banded Royal feed

The leaves of the Chinese Mistletoe are pinkish to red when young, turning light green and finally dark green as they mature. The mature leaves are stiff and slightly waxy. It should be noted, however, that several of the butterfly species' caterpillars actually feed on the flower buds and fruits of the Chinese Mistletoe, rather than the leaves.

A young shoot of the Chinese Mistletoe attached to its host via its specialised roots called haustoria

Like the Malayan Mistletoe, the Chinese Mistletoe is also mainly propagated by birds. Birds feed on the ripened globular fruits of the Chinese Mistletoe and once digested, the bird droppings are deposited on other plants as the bird moves in search for food. This gives a chance for the seeds to germinate and grow if a suitable host is found.

3. Rusty Mistletoe (Scurrula ferruginea)

The Rusty Mistletoe has a layer of fine brown hairs on the undersides of its leaves - giving it a "rusty" look

The last and slightly rarer species of mistletoe that plays host to butterfly caterpillars, is the Rusty Mistletoe. The leaves of this parasitic plant are green on top, but covered with a layer of fine brown hairs on the underside of the leaves, giving it a "rusty" appearance. As it grows, the main stem of the Rusty Mistletoe attaches to the host rather seamlessly, with a few side roots extending along the sides of the branch, growing the many little haustoria into the host.

The White Royal's caterpillars feed on the young shoots and leaves of the Rusty Mistletoe

This species of mistletoe is the caterpillar host plant for at least two species of Lycaenidae. These are:
  1. Great Imperial (Jacoona anasuja anasuja)
  2. White Royal (Pratapa deva relata
Both are rare species in Singapore. The White Royal was only recently re-discovered in 2007 but subsequently successfully bred on the Rusty Mistletoe.  The Great Imperial, which has been bred on all three mistletoes mentioned in this article, is the most versatile and its caterpillar accepts all three host plants.

A female White Royal perched on a leaf of the Rusty Mistletoe after ovipositing on the young shoots of the plant

Where it grows, the Rusty Mistletoe is not difficult to spot, as the brownish red appearance of its foliage sets it apart from its host. It grows into a relatively large bush that can measure 1-2m across. The flower of the Rusty Mistletoe has an interesting appearance of a brownish coloured hairy paw, whilst the fruit is a small hairy pseudo berry of about 1cm long.

Again, like the other mistletoes mentioned here, the Rusty Mistletoe is probably dispersed by birds that eat the fruits and then propagated by the bird droppings as the birds forage for food around the area. The seeds are also likely to stick onto branches of the host and then the haustoria anchoring the the plant to the host after the seed germinates, typical of the like the other species of stem hemiparasites.

In closing, we have taken a look at the more common mistletoes found in Singapore, and it is through keen observations with a dose of luck that we have discovered the range of species of butterflies that are dependent on these specific mistletoes for survival. If there is overzealous management of these "parasites" and their removal from their hosts, then it will critically threaten the existence of these species of butterflies (many of them rare) in Singapore. So the next time you see these parasitic plants around, leave them alone. The butterflies will thank you for that!

Text by Khew SK : Photos by Huang CJ, Khew SK, LohMY, Jonathan Soong and Horace Tan

References and Further Reading :