Happy Valentine's Day

Happy Valentine's Day
Tawny Coster (Acraea violae)

To the love-struck romantics and everyone who celebrate St Valentine's Day, have a wonderful and memorable evening with your loved ones.  Here's a pair of Tawny Costers (Acraea violae) in flagrante delicto.

The rose is red, the violet's blue,
The honey's sweet, and so are you.
Thou art my love and I am thine;
I drew thee to my Valentine:
The lot was cast and then I drew,
And Fortune said it shou'd be you.

from Gammer Gurton's Garland (1784)

 

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Random Gallery - The Lemon Emigrant

Random Butterfly Gallery
The Lemon Emigrant (Catopsilia pomona pomona)

The Lemon Emigrant is a common butterfly in Singapore, and can often be seen even in urban areas flying at its erratic and powerful speeds.  As the caterpillars of this species feed on several urban roadside species of Senna, it is widely distributed across Singapore from the city pocket parks to the nature reserves.  The Lemon Emigrant is polymorphic and occurs in at least seven different forms.

Photographed here, is a male form-hilaria one of the relatively common forms of the Lemon Emigrant.  It is predominantly lime green, with the distinctive red-ringed silver cell spots.  On the upperside, there is a thin black border on the forewings.  In parks and gardens, Lantana is one of the favourite nectaring plants of the Lemon Emigrant.

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Butterfly Mimicry and some recent findings

Feature : Butterfly Mimicry and some recent findings
Common Mormon - Common Rose mimicry : A discussion


A female form-polytes Common Mormon basks in the sun with its wings opened flat displaying the red spots that mimic the Common Rose's colouration

In the field of evolutionary biology, the mimicry theory as proposed by Henry Walter Bates in 1862 supported Darwin's natural selection theory.  Batesian mimicry was founded on a system comprising palatable mimics and unpalatable models.  Bates discussed the resemblance between insect prey that are defended by virtue of being "unpalatable" and those which lack such a defense. Batesian mimicry is therefore a form of deceptive mimicry because "palatable" prey deceive predators by their resemblance to species that predators find distasteful.

A open-winged Common Rose with its red/pink spots and body.  The species is known to contain Aristolochic acids in its body and is unpalatable to predatory birds

This theory of mimicry was further expanded by Fritz Muller in 1878 when he argued that, "if insectivorous birds learn to avoid unpalatable prey, and take a fixed number of given appearance during their education, then mimicry between unpalatable prey would be beneficial to individuals because the mortality costs of predator education would be partitioned out between members of the mimetic species." This approach spreads the chances of any one butterfly (or moth) being eaten over a larger number of species, and over a larger number individuals within a species. When a bird catches any one of these individuals, it quickly learns to keep away from all the species within the group.  This mimicry theory is now known as Mullerian mimicry.

Alfred Russell Wallace, the renowned 19th century naturalist, presented a paper on mimicry to the Linnean Society in March 1864.  In this work, where Wallace referred to Batesian mimicry, and demonstrated that mimetic resemblance could be limited to the female sex (sex-limited mimicry).  Wallace described data which showed that within edible species from the Papilio genus (such as P. polytes), mimicry of noxious model species occurs in the female, but not the male.  

It was thus with this background, that lepidopterists in Asia tend to consider the female Common Mormon (Papilio polytes) as a mimic of the unpalatable Common Rose (Pachliopta aristolochiae).  In the "Butterflies of the Malay Peninsula, 4th Edition" on page 70, this reference is also alluded to where it was written "... form-polytes, which is a passable mimic of Pachliopta aristolochiae, but can always be distinguished by its entirely black abdomen".

A mating pair of Common Mormon showing the "normal" male on the left, and the form-polytes female on the right.  Males are not the subject of mimicry and do not resemble any unpalatable models. 

Recently, in his 2006 paper presented in the Journal of the Lepidopterists Society 60(2), 2006, 82–85, Peter Smetacek of Uttaranchal, India, conducted experiments with various Papilio species and their palatability with birds.  Amongst these species was the Common Mormon (Papilio polytes).  Peter concluded that the "present findings prompt a re-interpretation of the relationship between polytes and Pachliopta . The classic Batesian interpretation of polytes-Pachliopta mimicry predicted that only polytes benefits at the expense of Pachliopta, which it “parasitises”, and predators, which it deceives into shunning palatable prey. The new Müllerian interpretation suggests that the shared aposematic signals of the co-models (polytes and Pachliopta spp.) result in enhanced predator learning and the benefits of this accrue to all the butterfly species involved. The relationship between the butterflies is one of asymmetrical Müllerian mimicry, since polytes appears to be only moderately distasteful while the Pachliopta genus is certainly more distasteful, with aristolochic acids in the body tissue."

A top view of a female form-polytes Common Mormon showing the red spots that mimic the Common Rose

Peter's study made reference to an earlier research that "Although the larvae of all Papilio butterflies are believed to be chemically protected by unpleasant taste and smell (Wynter-Blyth 1957; Klots & Klots 1959), this was not believed to be carried over to the adult stage except in the case of antimachus."

A top view of the Common Rose showing its red spots and body

Dr Krushnamegh Kunte, the author of the "Butterflies of Peninsular India, 2000, Universities Press" expressed his doubts with regard to Peter's experiments in the Journal of the Lepidopterists’ Society 61(1), 2007, 121–, and stated, as a concluding note, "The idea—that a classic Batesian mimic is actually a Müllerian mimic—is intriguing but controlled experiments are required before a definitive conclusion can be reached."  The Journal also printed, in the same edition, Peter's reply, standing by his conclusions on his earlier experiments, that the Common Mormon-Common Rose mimicry is Mullerian and not Batesian.

A female form-polytes feeding in flight.  Its slow unhurried flight also mimics that of the Common Rose

These recent arguments are thought-provoking and prompts further observations and discussions about the mimicry of a relatively common species here in Singapore. Some interesting observations that may be material for further arguments are listed for discussion :

A Common Rose displaying its aposematic red spots and body

(1) Typically, in the Batesian mimicry theory, the model is often more common than the mimic.  So there is some room for consideration in the case of the Common Mormon-Common Rose association, because in Singapore, the female form-polytes Common Mormon is the commoner of the two species.  The Common Rose is much rarer, and at times, not very often seen for months on end. Hence, if the mimic is more common than the model, then how successful is the protection by mimicry for the Common Mormon?

Mimic : A newly eclosed female form-polytes of the Common Mormon

(2) A second observation supporting the argument that Rutaceae feeders may be unpalatable would be the presence of at least four Great Mormon female forms in Singapore, when all of the unpalatable models have been missing for at least 3-4 decades of field observations here. One of the unpalatable models, The Common Clubtail (Pachliopta coon) does not even exist in Singapore, whilst the mimic form-distantianus occurs very rarely! In such a situation where there are only mimics and no models, even though the flight pattern of the mimics still resemble the original models, is there some evidence to suggest that these Rutaceae-feeding Papilio memnon are indeed unpalatable in the first place?

Model : A newly-eclosed Common Rose displaying its aposematic red spots and body

(3) However, if all Rutaceae feeders can sequester some form of distasteful chemicals in their bodies to make them unpalatable to varying degrees, does it mean that the common Lime Butterfly (Papilio demoleus), Banded Swallowtail (Papilio demolion), Blue Helen (Papilio prexaspes) and Great Helen (Papilio iswara) are all unpalatable as well?  Are there field observations to support this conclusion one way or the other? Or are some Rutaceae Papilionids able to sequester the distasteful chemcals from their host plants more adeptly than others?

A black hindwinged variant of the Common Rose that made its appearance in Singapore for a period of time in 2007 & 2008, and then as suddenly as it appeared, it disappeared for the past few years. 

(4) Also, an intriguing observation would be that, if the caterpillars of Rutaceae feeders like the Lime Butterfly and Common Mormon are distasteful, why is there a need for the first four instars of the early stages to camouflage themselves by resembling bird droppings?  Could it be that the concentration of the distasteful chemicals only reach an optimal amount to be effective when the caterpillars reach the final instars?  Or are there some other reasons? If not, why the need to camouflage yourself, when you are already distasteful?

A recent shot of a rather strange female Common Mormon that does not have any white markings on its hindwings at all!  Is it trying to mimic the "black" variant of the Common Rose?  Or is this just a rare aberration?

These recent findings and debates throw a new light on the classical Common Mormon-Common Rose mimicry theory and with further field observations and experiments, it is hoped that some researcher may reinforce Peter Smetacek's findings and support his conclusions, or on the contrary, prove that Wallace's theory for these two species continues to prevail.  Any of our readers out there who have field observations, photographs or other theories, please feel free to share them with us.

 

Text by Khew SK : Photos by Sunny Chir, Khew SK, Loke PF, Nelson Ong, Ellen Tan, Horace Tan, Tan Boon Huat & Anthony Wong

References :

• The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, The Malayan Nature Society, 1992.
• Butterflies. Dick Vane-Wright, The Natural History Museum, London, 2003
• Natural Selection and Beyond : The Intellectual Legacy of Alfred Russell Wallace, Oxford University Press, 2008
• The Book of Indian Butterflies, Isaac Kehimkar, Oxford University Press, 2008
• Butterflies of Peninsular India, Krushnamegh Kunte, Universities Press (India), 2000
• Smetacek, P. 2006. Some distasteful Asian Papilioninae (Papilionidae). J. Lep. Soc., 60:82–85.
• Kunte. K. 2007 : About distastefulness and mimicry : A comment on  Peter Smetacek's article
  (J. Lep. Soc., 60:82–85). J. Lep. Soc., 61(1), 2007, 121– 

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Happy Lunar New Year 2013!

Happy Lunar New Year 2013!
Welcoming the Year of the Snake

ButterflyCircle wishes all its Chinese readers all around the world a Happy and Prosperous Lunar New Year 2013! The photo featured here shows two recently-eclosed individuals of the Yellow Flat (Mooreana trichoneura trichoneura) placed together on a backdrop of a orange-red leaf. This shot was courtesy of ButterflyCircle member Sunny Chir.

Gong Xi Fa Cai! Xin Nian Kuai Le!

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Random Gallery - The Courtesan

Random Butterfly Gallery
The Courtesan (Euripus nyctelius euploeioides)

The Courtesan is a rare species in Singapore. There are certain periods in a year when an individual or two makes an appearance, after which the species completely disappears and not been seen for months, only to reappear again unexpectedly! It is not known to be a migratory species. There have been cases where its early stages - caterpillars and pupae, have been observed on its host plant, Trema tomentosa, which is a relatively common plant.

This male Courtesan was recently observed at a Park Connector and photographed by ButterflyCircle member Loke PF. The males have distinctive bright yellow eyes. Its forewings are deep bluish-black with a series of white spots and streaks. The underside is a pale brown with the white spots and streaks as on the upperside. There are two female forms of the Courtesan in Singapore, both of which are even rarer than the males. Both mimic the Magpie Crow a Danainae that is known to be distasteful to predators.

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Life History of the Yellow Flat

Life History of the Yellow Flat (Mooreana trichoneura trichoneura)

Butterfly Biodata:
Genus: Mooreana Evans, 1926
Species: trichoneura C & R Felder, 1860
Sub-Species: trichoneura C & R Felder, 1860
Wingspan of Adult Butterfly: 32-36mm
Caterpillar Local Host Plant: Mallotus paniculatus (Euphorbiaceae, common name: Turn-in-the-wind).

A newly eclosed female Yellow Flat showing its underside.

Physical Description of Adult Butterfly:

Both sexes are alike in coloration and markings. Above, the wings are dark brown with veins strongly dusted in white or pale yellowish brown. The forewing bears a number of round and stroke-shaped hyaline spots in the outer half of the wing. The hindwing has a large yellow tornal area and has yellow coloured cilia extending up to vein 6. Underneath, the forewing is dark brown with the same set of spots as above. The veins are not marked in white or pale brown. The hindwing is predominately white from the dorsum to vein 6, with the white coloration diffusing into spaces 7 and 8. The male has a hair tuft on its mid- and hind tibiae.

Close-up views of the legs of both sexes of Yellow Flat, the hair tuffs on the mid- and hind tibae of the male are visible.

Close-up view of the front part of a Yellow Flat taking nectar from Lantana flowers.

Field Observations of Butterfly Behaviour:

C&P4 describes Yellow Flat as being rare in the forested plain in Malaya. This holds true for this newly discovered species in Singapore (see this blog article for a report of the discovery in November 2012) as there has only been a handful of field sightings in the few months since the first sighting. The adult has a strong preference for dark and shady area, and rarely does it venture to sunny spots for sunbathing. The adults are fast and strong flyers and have the habit of perching with their wings opened flat.

A Yellow Flat taking nectar from Lantana flowers, note the hyalinity of the forewing spots.

Early Stages:

Although Igarashi listed Mallotus paniculatus and Macaranga triloba as host plants for the Yellow Flat, only the former has been found as the local host. The immature stages of the Yellow Flat feed on leaves of the host plant. Between feeding sessions, the caterpillars seek safety and concealment in a leaf shelter. The construction of the leaf shelter comes in two modes (to be described below). The caterpillars have been found to reside on leaves of the host plant at heights ranging from 1 metre (young plant) to several metres (mature tree) high.

Local host plant: Mallotus paniculatus.

A leaf of the host plant with a resident caterpillar of the Yellow Flat hidden in a leaf shelter (salmon-coloured arrow). A smaller (abandoned and opened) leaf shelter is nearby (red arrow).

The eggs of the Yellow Flat are laid on the upper surface of a leaf of the host plant. It is not uncommon to find a few (2-5) eggs on the same leaf from repeated oviposition runs to the same run. The whitish egg is dome-shaped with a base diameter of about 0.75mm. It is well hidden in a mass of dark brown and whitish hair. A number of longitudinal ridges run from the top of the egg to the rim of the base.

Two views of an egg of the Yellow Flat.

Left: a mature egg with the caterpillar already nibbed away part of the egg shel. Right: an empty egg shell after the emergence of the caterpillar.

The collected eggs take about 6-7 days to hatch. The young caterpillar emerges after it has eaten a sufficiently large upper portion of the egg shell. The rest of the egg shell is not eaten by the newly hatched which is about 1.8mm in length. At this stage, the body is orange in base colour. It has rows of short to moderately long white setae on its body surface, and a small tuff of white setae at the posterior end. The head capsule is orangy brown at the upper end and dark brown elsewhere. Several short white setae can be found on the head capsule too. A reddish to reddish brown band line the body side spiracularly.

Two views of a newly hatched caterpillar, length: 1.8mm.

A newly hatched caterpillar constructing its first leaf shelter. Left: making an initial cut through the leaf lamina. Right: the cut leaf segment is folded over.

A sequence of four shots showing the newly hatched caterpillar hard at work at folding the circular leaf segment over.

The newly hatched makes its way to a part of the leaf surface adjacent to a lateral vein to construct its very first leaf shelter. Here it cuts a near circular leaf fragment with a short stalk and folds it over towards and covers the lateral vein. The leaf fragment is held in place with silk threads. The leaf shelter is easily observed as the leaf fragment has the contrasting whitish underside exposed. The caterpillar ventures out of the shelter from time to time to feed on the leaf lamina in the vicinity. As the caterpillar grows, the body base colour assumes a pale yellowish brown coloration with a green undertone. After reaching about 3.5-4mm in about 5-6 days, the caterpillar moults to the 2nd instar.

Two views of a 1st instar caterpillar, length: 3.5mm.

The 2nd instar caterpillar has a yellowish green body covered with numerous tiny body setae. The reddish brown head capsule has a rough surface texture and also covered with many short setae. The body still has a lateral reddish brown band, but it is more diffused and less prominent than that in the 1st instar. This instar lasts about 5-6 days with the body length reaching about 5.5-6mm.

Two views of a 2nd instar caterpillar, early in this stage, length: 4.2mm.

Top: Late 2nd instar caterpillar dormant prior to its moult. Bottom: Newly moulted 3rd instar caterpillar.

The 3rd instar caterpillar differs from the 2nd instar caterpillar in having a body colour which is strongly whitish with a weak yellowish undertone. Typically at this stage, the caterpillar abandons its first shelter and moves to an adjacent spot to construct a larger but similar leaf shelter. This instar takes about 6-8 days to complete with body length reaching about 9-9.5mm.

Two views of a 3rd instar caterpillar, late in this stage, length: 9mm.

The resident and well eaten leaf of a 3rd instar caterpillar with its leaf shelter indicated with an orange arrow. Its abandoned 1st/2nd instar shelter is indicated with a red arrow.

Close-up view of the leaf shelter of a 3rd instar caterpillar.

Top: A late 3rd instar caterpillar dormant prior to its moult. Bottom: newly moulted 4th instar caterpillar.

The 4th instar resembles the 3rd instar caterpillar closely. The body base colour is pale yellow. The yellow tone is more intense early on in this instar, but as growth progresses and the body length increased, this tone lightens and the body appears more whistish. Numerous tiny yellow specks are visible on the body surface.

Two views of a 4th instar caterpillar, late in this stage, length: 14mm.

Early in the 4th instar, the caterpillar abandons its 2nd shelter (the leaf fragment making up the shelter is usually bitten off by the caterpillar as it does so) and goes on to construct a rather different looking shelter. Invariably the caterpillar selects a spot along the mid-rib closer to the leaf tip on the whitish underside. Here the caterpillar cuts one large fragment on one side, flips it over and secures it via silk threads to the other side to form the leaf shelter. Now the colour contrast is reversed compared to that seen in the previous 2 shelters. The caterpillar next cuts another large fragment on the opposite side and flip it over to form a loose roof over the shelter.

Leaf shelter for 4th and 5th instar caterpillars. Left: upperside view; Right: underside view.

Besides feeding on the leaf lamina on the resident leaf and adjacent leaves, the caterpillar also eats small and separated portions of the roof and ceiling of the leaf shelter, giving its a meshed or sieve-like appearance. The growth rates in this instar among the few caterpillars observed are rather variable, and the entire instar lasts about 6-11 days with body length reaching up to about 14-16.5mm.

Top: A late 4th instar caterpillar dormant prior to its moult. Bottom: Newly moulted 5th instar caterpiollar.

The 5th instar caterpillar has similar body markings and colour as in the late 4th instar. It is noteworthy that the dark reddish brown head capsules in the 3rd to 5th instars has 6-8 pale reddish brown spots just outside the frons area, and short white setae are restricted to the peripheral areas of the head. Typically the 5th instar caterpillar in the field continues to reside in the same leaf shelter used during its 4th instar and even goes on to use it as its pupation shelter. The 5th instar is rather long in duration and lasts for about 14-16 days, and the body length reaches up to 22mm.

Two views of a 5th instar caterpillar, early in this stage, length: 15mm.

Head capsules for the 4th instar (left) and 5th instar (right) caterpillars.

Two views of a 5th instar caterpillar,  early in this stage, length: 22mm.

On the last day of 5th instar, the body shortens in length and its colour turns to an intense tone of yellowish green. It ceases feeding and stays in the shelter. After purging its last few frass pellets, the pre-pupatory larva prepares for the pupal phase with a series of silk construction work with the main pieces being a silk girdle across the dorsum of its early abdominal segments, and a short and thickened transverse silk band on the substrate at its posterior end. Soon the pre-pupatory larva becomes dormant in its leaf shelter. Pupation takes place about 1-1.5 day later.

Two views of a 5th instar caterpillar, late in this stage, prior to constructing its pupal girdle, length: 18mm.

A girdled pre-pupa of the Yellow Flat revealed by partially opening the leaf shelter.

The girdled pupa is secured with its cremaster attached to the short transverse band on the substrate. A thin layer of whitish powdery substance envelops its body. It has a short thorax, a rather long abdomen and a short pointed and brown rostrum. The body is pale yellowish green, darker green in the wing case and brownish in the head area. It has a dark brown patch over its eye, a series of small round-shaped lateral spots just below the spiracles in abdominal segments 4-8, and usually has brown patches around the spiracles in these segments. Ventrally, there are dark brown patches, two to each segment, in abdominal segments 5-7. Length of pupae: 16-17.5mm.

Two views of a pupa of the Yellow Flat.

After about 8-9 days in the pupal stage, the development within the pupa comes to an end and the pupa turns dark brown to black in the wing cases and thorax. Overnight, the abdomen area turns dark brown to black and the adult butterfly emerges from the pupal case in the morning.

Two views of a maturing pupa of the Yellow Flat, night before eclosion.

Two views of a mature pupa of the Yellow Flat, minutes before eclosion.

A newly eclosed female Yellow Flat.

The empty pupal case after the emergence of the adult butterlfy.

References:

• [C&P4] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, The Malayan Nature Society.
• The Life Histories of Asian Butterflies Vol.2, Igarashi S. & Fukuda H., Tokyo University Press, 2000.
• Butterflies of Thailand, Pisuth EK-Amnuay, 1st Edition, 2006.

Text by Horace Tan, Photos by Nelson Ong, Simon Sng, Federick Ho, Sunny Chir, Khew SK and Horace Tan

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