31 August 2019

The Fruit Feeders

The Fruit Feeders
Fruit-feeding butterflies in Singapore

A Saturn (Zeuxidia amethystus amethystus) feeding on a fermenting fruit on the forest floor in the nature reserves

Butterflies' liquid diet can vary from nectar to carrion and sodium-rich puddles to fermenting fruits on the forest floor. This weekend's blogpost takes a look at some encounters of various species of butterflies that feed on overripe fruits and fruits of forest trees that are decomposing on the forest floor.

A pair of Archdukes feeding on rotting fruit

Not all species of butterflies feed on fruits that have dropped on the forest floor. These fruits that are produced by a variety of trees in the nature reserves of Singapore, either ripen and drop on the forest floor, or have been eaten by birds, macaques and other animals and the remains of the uneaten fruits fall onto the ground and ferment over time.

Four butterflies - Dark Blue Jungle Glory and Common Faun feasting on rotting fruit on the forest floor

When fruits start to rot, the main product of the fermentation process is likely to be acetic acid. Whilst the flesh of many fruits contain several types of sugars, the concentration of lactic acid during the fermentation process is an indicator of a just-ripe fruit with maximum sugar content. This is why when a fruit is not ripe enough or too ripe, butterflies are not attracted to them. Hence there appears to be an optimal period during the fermentation process where butterflies can be found feeding on the fruits.

Three Saturns feeding on discarded overripe pineapples on the forest floor

A Dark Blue Jungle Glory foraging amongst fallen fig fruits

So, do all butterflies feed on rotting fruits? The answer, as with many things to do with butterflies, is "it depends". Not all species of butterflies feed on fruits, and there are cases where certain fruits only attract some species, whilst other fruits attract different other species. Generally, the forest-dependent fruit-feeding species are largely from the sub-families Satyrinae, Limenitidinae, Charaxinae and Nymphalinae. Even so, not all species in the sub-families mentioned above are fruit feeders. Field observations show that quite a number of the fruit-feeders are those that prefer low-light conditions and keep low on the ground in the shaded forest understorey.

The ripened fruit of the Singapore Rhododendron (Melastoma malabathricum) attracts a Bush Brown and an Arhopala - a rare sight in itself, as Arhopalas are rarely seen to feed 

Amongst the six families of butterflies, the Papilionidae, Pieridae, Riodinidae, Lycaenidae and Hesperiidae species are very rarely observed feeding on fruits. With some exceptions of some Lycaenidae, which have been observed feeding on the ripened fruits of the Singapore Rhododendron (Melastoma malabathricum), it is pretty rare to see a Lycaenidae feeding on rotting fruits on the forest floor.

The Common Faun feeding on fallen fruits

Amongst the fruit feeding species that are regularly observed on fermenting fruits on the forest floor, are species like the Common Faun (Faunis canens arcesilas), Saturn (Zeuxidia amethystus amethystus) and Dark Blue Jungle Glory (Thaumantis klugis lucipor). It is also likely that the recently confirmed Dark Jungle Glory (Thaumantis noureddin noureddin) would also be attracted to such fermenting nectar source.

Amongst the Limenitidinae, the Malay Viscount and Malay Baron are often observed to feed on fallen fruits along forest footpaths

Amongst the species of Euthalia and Tanaecia/Cynitia we have observed the Malay Viscount (Tanaecia pelea pelea) and the Malay Baron (Euthalia monina monina), feeding on rotting fruits on the forest floor. Other species in these two genera have not been so often observed to display this behaviour and more field observations can be made to validate this.

The Archdukes, Rajahs and Nawabs are often "customers" of overripe fruit on the forest floor

All three species of the Lexias have been encountered to feed on rotting fruits on the forest floor. Both males and females of the species are equally attracted to the fruits when the sugar content from the fermentation process is optimal. Amongst the Charaxes and Polyura species, some have also been observe to like feeding on rotting fruits.

A sample of the type of fruits that, when ripened and fall on the forest floor, attract butterflies

In Singapore's forests, fruits of various species of figs (Ficus spp) that have fallen on the floor are the most popular source of sugars for these fruit-feeding butterflies. There are many species of figs growing in our forests, and these are a good source of sugars for these species of butterflies, besides being food for the animals and birds.

A Common Evening Brown feeding on overripe Jambu Air at Sg Buloh Wetland Reserve

And then there are other cultivated fruits like the pink Jambu Air or Water Apple, tends to also attract some species like the Common Evening Brown (Melanitis leda leda) and the Bamboo Tree Brown (Lethe europa malaya). There are also several species of the jambu (Syzygium spp) where the fruits attract butterflies. On Pulau Ubin and Sg Buloh Wetland Reserve, we have observed butterflies feeding on the fruits when the trees drop their overripe fruits on the floor. Other species like the Bush Browns (Mycalesis spp) and Common Palmfly (Elymnias hypermnestra agina) are also attracted to some of these fruits.

A Palm King feeding on discarded watermelon

The large Palm King (Amathusia phidippus phidippus) is another species that can be found feeding on fruits. We have had a couple of observations of several individuals of this species feeding at discarded fruits from a roadside fruit vendor in Malaysia. In the picture above, the Palm King was photographed feeding on a half-eaten watermelon that had been thrown away along a footpath at Chestnut Nature Park.

Butterflies feeding on fruit servings in commercial butterfly parks.  A Yellow Barred (now extinct in Singapore) feeding on overripe banana and a Palm King feeding on pineapple at Entopia, Penang

In commercial butterfly parks, one can often see many species of butterflies feeding on rotting banana, papaya, mango, pineapple and many other sugar-laden domestic fruits that are left to ferment on artificial feeders. There are also many websites that teach butterfly gardeners how to use fruit hangers to attract butterflies to their gardens.

Text by Khew SK : Photos by Khew SK and Loke PF

24 August 2019

Flying Tigers 2.0

Tiger Refresh!
An Update of the Flying Tigers of Singapore

Some time back in January 2008, our weekend blogpost featured the Flying Tigers of Singapore. More than 11 years ago, there were 5 extant Danainae species that were referred to as "Tigers". Their common names probably originated from their striped appearance, and in some of the cases, the orange colour and/or stripes, reminiscent of the Malayan "Pak Belang".

Over the years, at least three other species appeared in Singapore and were spotted by eagle-eyed butterfly watchers and photographers. All these species have been classified as vagrants as sightings of them have been infrequent, and in some cases, only from a single chance encounter.

The Tigers belong to the subfamily Danainae, relatively large and slow-flying butterflies that are usually distasteful to predators. This is due to their caterpillar host plants that are lactiferous and in most cases, contains toxic substances which the caterpillars sequester to give themselves a "chemical protection" against predators.

The majority of species in the subfamily Danainae also display aposematic colouration, which is nature's way of communicating to would-be predators that the butterfly should be avoided, unless the predator is asking for some trouble. The characteristic stripes, iridescent colours or bright and showy colours of the Danainae are good examples of aposematic warning colouration that other butterflies and moths mimic to provide some measure of protection for themselves.

Today, the 5 extant species of Tigers that we featured in the 2008 blogpost are still doing fine, and over the past decade, where urban parks and gardens have cultivated more Tiger-friendly host and nectaring plants, they have become more common. These five species - The Plain Tiger, Common Tiger, Black Veined Tiger, Blue Glassy Tiger and Dark Glassy Tiger are still often seen feeding at the flowers in parks and gardens.

In Oct 2014, another species of the genus Ideopsis, the Grey Glassy Tiger (Ideopsis juventa sitah) was observed at Pulau Ubin, and then subsequently in the same year, at the Singapore Botanic Gardens. This species is not uncommon up north in Johor, and has been seen in numbers at the Desaru area on the eastern coastal areas of Johor.

It is possible that an outbreak of the species has sparked off some strays into Singapore. It has not been reliably seen in recent years after the sightings in 2014, but added to the Singapore Butterfly Checklist as a vagrant species appearing in Singapore.

In 2016, a free-ranging Dark Blue Tiger (Tirumala septentrionis septentrionis) was photographed in the field. The Dark Blue Tiger has been sighted previously but no photographic evidence of a Singapore field-shot individual was recorded so far. Also, at that time, the butterfly aviaries in Sentosa, Hort Park (now closed) and Changi Airport also imported this species from Malaysia and there may have been escapees.

In Jan 2019, another wild shot individual was posted from Pasir Ris Park. Although still considered a vagrant species, the Dark Blue Tiger was added to the Singapore Checklist and 'adopted' as one more flying tiger in Singapore.

Also in 2016, a single individual of the Blue Tiger (Tirumala limniace) was spotted at a suburban garden feeding on Crotalaria retusa. The Rattlebox Weed is a favourite plant of the Danainaes where they feed on the sap of the stem and seedpod of the plant. A rare species even in Malaysia, it was therefore a surprise that a pristine vagrant appeared in Singapore.

Perhaps, as the author suggested, the Blue Tiger shot 5 years ago was a stowaway on a plant that was imported to Singapore as a pupa, and then eclosed here. Other than this individual, so far no other sighting of the Blue Tiger has been made in Singapore since.

This is the latest inventory of "Tigers" in Singapore, with a total of eight sighted and recorded over the years.  Let us hope that there will be other Tigers that will make their way to Singapore in the coming years.  

Text and Photos by David Chan, David Ho, Mei Hwang, Khew SK and Loke PF

18 August 2019

Butterfly of the Month - August 2019

Butterfly of the Month - August 2019
The Indian Cupid (Everes lacturnus rileyi)

The year moves into the peak of summer and the heatwave that is spreading across the globe is a constant reminder of climate change and global warming. Again, reports of unprecedented high temperatures in many countries are in the news - from Europe to Japan. Back in Singapore, it has been quite a few weeks since we had ample rainfall, and we can see wilting plants, dried undergrown and brown grass patches all over the island.

The National Environment Agency's Meteorological Service Singapore said earlier this month that it forecasts drier-than-normal weather conditions here and in the surrounding region in the coming weeks, following a record dry July. Drier weather can be expected from August to October this year. This followed two bush fires in Singapore recently where parch-dry wastelands are vulnerable to anything that sparks the dried grasses and twigs to start a fire going.

Always in the news, the continuing trade war between China and the US, and how it is going to impact the global economy and change lives. More countries seem to be jumping on to the bandwagon to start their own trade disputes. However, the impact of the trade war between the two economic giants will be felt throughout the world and little Singapore will certainly not be spared. Already, local trade reports point to a technical recession in the coming quarter and a possibility of a worse outlook ahead in 2020.

And then the Hong Kong protests. It is almost impossible to read news - whether online or in hardcopy print, without some mention about the civil unrest in Hong Kong. It is amazing to see how the citizenry, when pushed to a corner, can retaliate in a way that may almost irreversibly affect a country's stability. Singaporeans reflect over what is happening in Hong Kong, and many say that it would/could never happen here because of different circumstances and political outcomes.

A mating pair of Indian Cupids

The hot and dry weather in Singapore seemed to have some impact on our butterfly activity. Other than very dry undergrowth that affects plants in general - the lifeline of butterflies, activity across the island has only reduced somewhat. Curiously, certain species that have not appeared for quite some time have suddenly reappeared, whilst some trees reacted to the harsh weather by flowering and attracting butterflies to come out from their forest hiding places.

A pristine male Indian Cupid with its wings opened partially

Our August Butterfly of the Month is the diminutive and rare Indian Cupid (Everes lacturnus riley). With a wingspan of only about 20-25mm from wingtip to wingtip, this small butterfly frequents open grassy areas in sub-urban wastelands in Singapore. It was first observed in various areas on Pulau Ubin and Pulau Tekong, but then appeared in wastelands at Punggol and parts of Central Catchment along the forest edges.

The Indian Cupid (or referred to as the Tailed Cupid in some literature) is the only representative of the genus Everes in Singapore. The male butterfly is purple-blue on its uppersides, with narrow black borders on both wings. The female is a drab brown above with a pair of orange-crowned spots at the tornal area of the hindwings.

An Indian Cupid perched on a grass flower with its proboscis partially unfurled

The ground colour of the underside is a pale grey, marked with the usual Polyommatinae spots and streaks. The pair of large orange-crowned black spots at the tornal area of the hindwing helps to distinguish this species from several other lookalikes in Singapore e.g. the Gram Blue. The pair of long filamentous white tipped tails at vein 2 of the hindwing also helps to separate the Indian Cupid from other similar species.

An Indian Cupid perches on a grass blade on a hot sunny afternoon

The Indian Cupid has a weak erratic flight and typically flies low amongst shrubbery. The butterfly can often be found in the vicinity of its caterpillar host plant, Desmodium sp. that thrives in newly cleared roadside tables and wastelands. When active, it is skittish and not easy to approach for a good shot. However, after some time of flying restlessly, it rests with its wings upright on grass blades or on the tops of leaves.

Being a small butterfly, it can be overlooked, or confused with other lookalike Lycaenidae like the Nacaduba, Prosotas or Euchrysops. Its flight characteristic is similar, hence any small butterfly fluttering erratically amongst low bushes and grassy areas should be given a second look to ascertain its identity. Where it occurs, there are often sightings of more than just one individual. However, it can disappear from a location for years, before re-appearing again elsewhere.

Text by Khew SK : Photos by Khew SK, Koh CH, Loh MY and Jonathan Soong