29 June 2008

The Butterfly Proboscis

A Butterfly's Proboscis - Its Lifeline to Survival

Butterflies are well-known for their beauty and grace and are one of the most admired and adored creatures of the insect world. Most people are aware that butterflies do not have chewing or biting mouthparts, nor have any sort of defensive mechanisms which scratch, sting, bite or poke, unlike most other insects. How then do these pretty and harmless insects derive their sustenance for survival?

They feed on a liquid diet through their adult life, imbibing dissolved sugar, salts and other minerals from a variety of sources ranging from flowers, rotting fruit, tree sap, carrion, urine, faeces and so on. Some species are also partial to human sweat and will stop to feed on sweaty forearms, faces and hands of humans who are in the vicinity of these hungry butterflies!

A Malayan Eggfly uses its proboscis to suck up human sweat!

Butterflies feed through a paired tube located at their heads. This paired tube is called the proboscis. The Greek origin of proboscis comes from "pro" (before) and "boskein" (to feed). The word proboscis is pronounced in two different ways, both of which are acceptable - (pro-BOSS-iss or pro-BOSS-kiss). Click on the links to hear the pronunciation of the word proboscis.

Through the amazing process of metamorphosis, the caterpillar's biting/chewing mouthparts - for eating their host plants, transforms into the paired "drinking straw" proboscis. When the butterfly ecloses, besides pumping fluids into its limp wings to expand them, it also has to get its proboscis in working order. As it ecloses from its pupal case, the butterfly's proboscis is in two separate pieces that are joined together by tiny hooks and fringes. The eclosing butterfly has to twist and curl the two halves of the proboscis to create one drinking tube. If, in the event this preparatory function is interrupted, the butterfly can no longer feed, even though it is able to fly, hence condemning it to a short life of hunger and starvation.

Situated between the butterfly's eyes, but below them, is the proboscis. This paired structure, comprising two halves, are hooked together after eclosion, forming a central canal. The proboscis is usually coiled up like a watchspring right against the butterfly's face, to protect it. When in use, it is extended with muscles to probe the nectaries of flowers or other substances. When outstretched in this manner, the proboscis behaves like a drinking straw through which the butterfly draws fluids up and into its body. Commonly 1 to 2 cm long in butterflies, the proboscis can be as long as 30cm(!) in certain Hawkmoths. Indeed, the proboscis of certain species of Hesperiidae (Skippers) are typically longer than the body of the butterfly, sometimes twice as long.

The proboscis of this Hoary Palmer is more than twice as long as its body!

The proboscis appears to be protected by the butterfly's labial palp. The two palpi line up along the butterfly's face, between which the proboscis lie. In certain species' case, the palpi are so hairy as to give the butterfly an appearance of an unshaven face.

When a butterfly finds a potential food source, it unfurls its proboscis and uses its forked tip to investigate the fluids. The proboscis is therefore a very useful tool and particularly well-adapted for the butterfly to reaching deep into flowers for nectar. In the process of feeding on the flowers' nectar, butterflies also transport the pollen from the stamens of a flower to other flowers as the butterfly moves around to feed, thereby helping in the process of pollination. Indeed, butterflies are also one of the agents of pollination and contribute to the propagation of many of the plant species on which the butterflies feed on the flowers.

The proboscis of the Plain Tiger is covered with pollen from the flower, all ready to be transferred to the next flower for pollination, as it goes about feeding on nectar.

The proboscis is also used when the butterflies puddle (the act of feeding on damp footpaths or river banks) where they imbibe dissolved salts and other minerals from the fluids on the ground. The proboscis is similarly used when the butterfly feeds on tree sap, rotting fruit, bird droppings and a whole spectrum of dissolved minerals from these sources that the butterfly requires for sustenance, fertility and energy to go about its daily activities.

The proboscis is very much sized according to the size of the butterfly, with larger butterflies having longer and thicker proboscis whilst the smaller butterflies have thinner and finer proboscis. An interesting observation is that the proboscis of butterflies also come in various colours - ranging from jet black to orange and greens.

A display of multi-coloured proboscis as these butterflies feed on rotting fig fruits on the forest floor.

Text & Photos by Khew SK

Special Acknowledgments to :

  • Merriam-Webster Online for the Audio pronounciation clips

References :

  • Handbook for Butterfly Watchers : Robert Michael Pyle, Houghton Mifflin Company, Boston/New York, 1992

25 June 2008

The Life History of the Great Helen

Life History of the Great Helen (Papilio iswara iswara)

Butterfly Biodata:
Genus: Papilio Linnaeus, 1758
Species: iswara White, 1842
Subspecies: iswara White, 1842
Wingspan of Adult Butterfly: 140mm
Caterpillar Host Plants: Maclurodendron porteri (Rutaceae)

A male Great Helen visiting a flower.

A male Great Helen visiting a flower, giving a view of its upperside

Physical Description of Adult Butterfly:
Great Helen is a large butterfly with a wing span of up to 14cm. The forewing is black above and, on both surfaces, the hindwing has a large white discal patch of four spots in spaces 4 to 7. There is a spatulate tail at each hindwing at vein 4. On the hindwing underside, there are blue post-discal lunules distal to the white spots in 2, 3 and 4. The female has a large black ocellus ringed with red in each of spaces 1a and 2 on the hindwing upperside (see the top picture in this article).

Field Observations of Butterfly Behaviour:
Locally the occurrence of this species is restricted to the Central Catchment Nature Reserves where its host plant, Maclurodendron porteri (old name: Acronychia porteri), is rather common, especially along MacRitchie Nature Trail and Nee Soon Pipeline. The adults usually fly rapidly at tree-top height, except when they come down to feed at flowering bushes or to look for oviposition sites. Like many of the Papilio species, when an adult stops to feed at flowers, it flutters its forewings while its hindwings are kept relatively still. When resting at a perch, the forewings droop backwards to almost or completely conceal the white discal patch on the hindwings.

Early Stages:
The host plant, Maclurodendron porteri, is a tree with simple, opposite and ovate leaves which are 10-18cm long. The leaves have a pleasant aromatic smell when crushed or when broken at stalks. Cancer researchers have found this plant to contain various flavonols with cancer-fighting attributes.

Host plant : Maclurodendron porteri

A female Great Helen attempting to oviposit on a leaf of the host plant

The eggs of the Great Helen are laid singly on undersides of young leaves of the host plant. Typically only one egg or one caterpillar is found on a single plant. The egg is pale creamy yellow with a finely roughened surface. It is nearly spherical with a diameter of about 1.8mm.

A fresh egg of Great Helen, diameter: 1.8mm

A mature egg, giving a faint front view of the head of the caterillar.

The egg found in the field took about 4 days to mature. The young caterpillar eats its way out of the mature egg, and then proceeds to finish up the rest of the egg shell. The newly hatched has a rather spiky appearance, and an initial body length of about 4mm. It is greyish white dorsally and dark brown laterally,

Newly hatched 1st instar caterpillar, length: 4mm

1st instar caterpillar, length: 6mm

In the first 4 instars, the Great Helen caterpillars look like bird droppings as they rest on the leaves. The resemblance in the 3rd and 4th instars are stronger with the body also assuming a slimy appearance. As in the case of all Swallowtail butterflies, the Great Helen caterpillars in all instars possess a fleshy organ called osmeterium in the prothoracic segment. Usually hidden, the osmeterium can be everted to emit a foul-smelling secretion when the caterpillar is threatened

As the 1st instar caterpillar grows to a maximum length of about 8mm, the dorsal whitish patches changes to orangy brown. There is a faint whitish saddle on the mid-abdominal segments, and white markings on the posterior abdominal segments. After about 3 days in 1st instar, the caterpillar moults to the next instar.

1st instar caterpillar, day 3 in this stage, ready to moult; length: 8mm

The 2nd instar caterpillar has a similar appearance to the late 1st instar caterpillar except for the more distinctly white saddle mark and posterior abdominal segments.
This instar lasts 3 days with the body length reaching about 16mm before the next moult.

2nd instar caterpillar, length: 10.5mm

In the 3rd instar, again there is no drastic change in physical appearance except for more dark brown to black patches appearing on the mottled body, and the more distinct white saddle mark. This instar takes 3 days to complete with body length reaching 25mm.

3rd instar caterpillar, length: 25mm

The 4th instar caterpillar looks almost the same as in the 3rd instar but with a more slimy appearance. This instar lasts 4 days with body length reaching about 38mm.

4th instar caterpillar, length: 36mm

The next moult brings the caterpillar to its 5th and final instar. Now there is a drastic change in appearance. There are two eye spots on the third thoracic segment, a transverse band at abdominal segments 1 and 2 , and oblique bars at mid-abdominal segments. After the moult to 5th instar, the body ground color is initially mottled green, but this changes gradually to the characteristic smooth green color after 1 day.

5th instar caterpillar, first day after the moult, length: 39mm

Now the shield-like thorax is very prominent. The eye spots on the 3rd thoracic segment are connected by a transverse green dorsal band with sinuous markings. A similar band, but in orangy brown, occurs between abdominal segments 1 and 2, and features pale purplish gaps between the sinuous markings. The first oblique bars, one on each side, run from the base of abdominal segment 3 to the top of segment 4. The second oblique bars occur at the two sides of abdominal segment 5, wide at the base and tapering to the dorsum. Both sets of oblique bars are mainly greenish brown dotted with tiny pale purple spots.

5th instar caterpillar, late in this stage, length: 65mm

The 5th instar lasts for 8 days, and the body length reaches up to 65mm. Toward the end of this instar, the body gradually shortens in length. Eventually the caterpillar comes to rest on the lower surface of a stem and becomes a pre-pupatory larva.

A pre-pupatory larva of Great Helen

Pupation takes place a day later. The pupa suspends itself with a silk girdle from the stem. It is mottled in shades of brown, green and white. The pupa has cephalic horns and a dorsal thoracic hump, and is angled in side view. Length of pupae: 36-37mm.

Pupa of Great Helen; fresh on left and mature on right

After 13-15 days of development, the pupa turns black as the development within the pupal case comes to an end. The next day the adult butterfly emerges from the pupal case. The beautiful undersides of its wings are fully displayed as it dries its wings for the first few hours after eclosion.

A newly eclosed female Great Helen drying its wings near the empty pupal case

A newly eclosed male Great Helen


I would like to express my gratitude to Samsuri Ahmad of NParks for generous assistance in the identification of the host plant.


  • The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society.
  • The Butterflies of Hong Kong, M. Bascombe, G. Johnston, F. Bascombe, Princeton University Press 1999
  • Plants that Fight Cancer, S.E. Kintzios, M.G. Barberaki, CRC Press 2004
Text and Photos by Horace Tan

21 June 2008

Butterfly of the Month - June 2008

The Royal Assyrian (Terinos terpander robertsia)

The Royal Assyrian belongs to the butterfly sub-family Heliconiinae of the family Nymphalidae. The genus Terinos features medium sized butterflies with angled wings. Of the three species found in Malaysia and Singapore, only the Royal Assyrian is known to exist in Singapore. All three species are rich purple above with white or pale orange area on the hindwings.

The Royal Assyrian is not uncommon in Singapore, and can be found in the nature reserves where its host plant, Rinorea anguifera (Violaceae) grows. Seasonally, several individuals are encountered together in the vicinity of its host plant. The species is most often seen along MacRitchie Nature Trail and on the fringes of some of the reservoir parks.

Males are sometimes observed puddling along damp paths in the forests. A peculiar behaviour of the species is that some individuals, when disturbed, fly and stop on the undersides of leaves with their wings folded shut. The Royal Assyrian is not a particularly strong flyer, but flits from leaf to leaf in the shaded understorey of the forested areas. When alarmed, however, it takes off quite quickly to the treetops.

In the early morning hours, they can be observed to open their wings flat to sunbathe, displaying the attractive rich purple colours of the uppersides of the wings. The spectacular purple upperside of the wings are a sight to behold and is quite unlike any other butterfly species in Singapore.

Text by Khew SK : Photos by Federick Ho, Tan BJ, Horace Tan, Bob Cheong, LC Goh and Khew SK

15 June 2008

A Northern Painted Jezebel visits Singapore!

A Northern Painted Jezebel visits Singapore!

Not exactly of the winged variety, but a good friend of ButterflyCircle, Mr Leslie Day, resident of Koh Samui in Thailand. Leslie goes by the nickname of Painted Jezebel on the ButterflyCircle forums.

Les and his latest el-cheapo tree-pod - an effective newly-patented improvisation to replace image stablisation

Leslie Day is a renowned authority on the butterfly Pierine genus Delias and has spent a great part of his life pursuing and documenting the complete list of all the species and subspecies of the genus on his website, Delias of the World.

Les, as most of us call him, is a former banker from England, who is happily spending his well-deserved retirement on the resort island of Koh Samui in Thailand for the past year or so, visited Singapore in late May 08 for a week. His mission : to photograph as many species of Singapore butterflies as possible.

ButterflyCircle member Wong calling a butterfly down for our visitor to shoot

A groupie mugshot of ButterflyCircle members with Les at Pulau Ubin

Not to be dampened by a few days of wet weather and a malfunctioning zoom lens during the time he was here, Les and ButterflyCircle members went out with a vengeance to see how many species Les could shoot in the 6 days he was here. From Ubin to Central Catchment nature reserves and urban parks, the team set out to find Singapore's forest and urban butterflies. (His final photographic tally was +35 species and a further 6 species spotted - all of which were "new" to Les. Of course, many others which also can be found in Koh Samui were not included in this list)

Shoot, shoot & shoot - rain or shine...

Les and ButterflyCircle members hard at work in the field

ButterflyCircle members who joined Les on his quest also enjoyed themselves thoroughly - rain or shine. There was even a dinner organised for Les, where prominent Harvard researcher, Dr David Lohman also joined in the fun discussion. Members who were having trouble with tongue-twisting Latin names of the butterflies were entertained with a session of rather alien language as the experts exchanged notes on their beloved hobby.

Groupie mugshot with Dr Lohman and Les at a scrumptious buffet dinner

Our generous Les even presented a S$100 book voucher to ButterflyCircle's youngest member, Aaron Soh, who made the best guess on the number of species in Les' checklist of Koh Samui as at end 2007.

Les presenting the $100 Book Voucher to ButterflyCircle's youngest member at SBG

I'm sure our visitor from Koh Samui enjoyed himself, being well-entertained by the enthusiastic members of ButterflyCircle, as well as being amazed by Singapore's butterfly fauna and rich biodiversity, despite being a developed modern city in Asia.

Here are some of the photos of the butterflies that Les managed to nail during his visit here.

Report by Khew SK : Photos by Les Day, Bobby Mun, Simon Sng, & Khew SK