The Atlas Moth Chronicles - Episode 2

The Atlas Moth Chronicles
Episode 2 : The Transformation is Complete

Dr Wee is back to share with us his meticulous up-close-and-personal documentation of the metamorphosis of the Atlas Moth from egg to adult.  

The unexpected arrival of a pair of Atlas Moths (Attacus atlas) at my porch left me with about 250 eggs.  These eggs were transferred to the leaves of Limau Purut (Citrus hystrix) branches held in vases. 

A batch of Atlas Moth eggs - usually pinkish in colour

The rearing of this batch of eggs was to be a learning process. Many failed to survive during the 60-70 days period before pupating. Only four caterpillars survived to turn into pupae and of these only two successfully eclosed. Fortunately the moths that emerged were both females. They attracted males and mated to produce a second generation of eggs. The mating pairs had to be caged as otherwise they would fly off with the females laying their eggs elsewhere.

A caged female Atlas Moth lays her eggs after mating

These eggs, double the number of the first batch, made it necessary to use additional alternative host plants like Starfruit (Averrhoa carambola) and Blue Mahang (Macarange hyeni).  My Limau Purut tree would not be able to support this larger number. The caterpillars developed well with all the plants and allowed further observations on their development that were missed during observations on the first batch. These second generation eggs eventually gave a total of 18 pupae.

Maintaining and observing these caterpillars were a full time job. Their voracious appetite demanded daily, or sometimes twice daily, provisions of new branches of their food plants. The water in the vases needed regular changes - after all I was breeding moths, not mosquitoes!

1st instar Atlas Moth caterpillars just after hatching from their eggs

Within nine days most of the eggs hatched into 7 mm grey-white caterpillars with black heads. Projecting from each segment was a ring of tubercles, the tips covered with a tuft of black hairs.  The first thing these tiny caterpillars did was to eat up the eggshells.  As they grew, they moulted at regular intervals and produced small pellets of frass. These pellets were colourful among the caterpillars feeding on Starfruit leaves, brown on Limau Purut and darker brown on Blue Mahang. Frass of older caterpillars failed to show such differences in colour.

Atlas Moth frass.  Clockwise from top left - on Starfruit, Limau Purut, Mahang, and frass of older caterpillars

It was relatively difficult to spot the early moulting as the process lasted a few minutes and the emerging caterpillar immediately ate up the discarded skin, leaving no traces. However, with later moults, the caterpillars did not to eat the old skin, or if they did so, they took their time, thus it was relatively easy to spot them.

 

Moulting Atlas Moth caterpillars

The second instar caterpillars had a distinctly different appearance from the first - white with patches of orange all over and an orange head. The third instar caterpillars showed a pair of anal claspers each with a distinctly large orange spot. The body remained white with patches and tiny spots of orange that disappeared with age.  Older caterpillars turned white with grey-green spots and a light green ventral surface. The final instar caterpillars took on a darker green colouration.

 
 
 
 

Various instars of the Atlas Moth caterpillars

Moulting was documented during the final moult. The skin suddenly appeared dried and wrinkled. The old skin then turned white and translucent]. Contracting and expanding its body continuously helped the caterpillar separate the old skin from the new.  Further vigorous movements caused the old skin to split around the anterior end.  All this time the caterpillar was firmly attached to the twig with the help of the anal clasper. Wriggling and forward movement with the help of its prolegs helped it move out of its old skin to eventually leave it behind. The entire process took less that half an hour.

http://www.youtube.com/watch?v=dEnGa0_hyEU&feature=plcp

http://www.youtube.com/watch?v=bKPlpDa21Uc

Exactly when the caterpillar molted varied with the individuals, some occurring earlier than others. It took 50-57 days for the first batch of caterpillars to start pupating from hatching and only 38-52 days in the case of the second batch.

As mentioned earlier, the first batch of caterpillars ended in four pupae of which two successfully eclosed. With the second batch, there were 18 pupae and all eclosed.

When a caterpillar had grown to its full size after weeks of intermittent feeding, it rested for some time before proceeding to the next stage of its metamorphosis. It then voided its stomach content, a greenish liquid containing numerous tiny pieces of undigested leaves. The caterpillar then became restless, moving about the twigs for up to 36 hours, apparently in search of a suitable spot to pupate. This, of course was under “culture” conditions. We do not know what happens in the wild.

 
 

Pupating sequence of an Atlas Moth caterpillar

Once the caterpillar was satisfied with the spot, it moved its body sideways, spreading a layer of silk on the leaf surface . At the same time it spread silk around the leaf stalk and its attachment to the twig. This was to ensure that the leaf it was pupating on would not get detached from the twig before eclosure. Only then did the caterpillar begin to create a silk cover over itself. The completed pupa on a Limau Purut leaf was a neat elongated structure, 6-7 cm long and 2.5-3 cm wide. With the compound leaves of Starfruit, a number of leaflets would cover the pupa.

 

Pupae of Atlas Moth cats on two different host plant leaves

Silking took more than 12 hours to complete
http://www.youtube.com/watch?v=qrbQgrwF2wI&feature=plcp

Sometimes the pupating caterpillar discharged a liquid that dripped from the bottom of the pupa case. It would be another 22-29 days before the adult moth appeared.

Trying to catch the moment of eclosion was elusive to say the least. For three weeks my vigil was long and tedious, sometimes  even sleeping with the pupae by my side. After all, eclosion can happen any time of the day or night. And exactly how many days to eclosion varies. The first two pupae from the early batch of caterpillars eclosed after 25 days. Knowing this did not help as those from the second batch developed a few days earlier. However, having 18 pupae to keep track with was helpful.

The first three eclosions of the second batch occurred during the early hours of the morning, probably between 0400-0500 hours. The fourth pupa took me by surprise when it eclosed during the evening. After four failures I got lucky with the fifth. It also happened in the evening. I was watching the pupa. There were scratching sounds from within. Unfortunately in a moment of inattention the emerging moth simply crawled out of the pupa case in less than a minute. I missed the crucial moment of emergence but managed to document the subsequent sequences.

I was successful in catching the emergence of the adult moth on video only with the ninth pupa. The process was long and tedious as the apical opening of the pupa case was apparently a little too small. The entire process took 6 minutes and the moth then hung from the bottom of the case until its wings were fully expanded.

http://www.youtube.com/watch?v=0fMaK6l28RM&feature=plcp

The next eight pupae eluded me as eclosion came mostly in the early morning, with two in the evenings. However, a second successful encounter came with the last pupa where the adult squeezed easily through the small opening of the silken case in less than 3 minutes.
http://www.youtube.com/watch?v=e9jx--mcsrI&feature=plcp

Since my first encounter with Atlas Moths in 2004, I have been obsessed with finding out how the adult moth emerges from the pupa case. So finally I have satisfied my curiosity and I have two video clips to show for it.

Once the adult moth had emerged from the pupa case, it crawled down to the lower end and hung out its wings as fluids from its abdomen were pumped through the veins until the wings became fully expanded. This can take up to two hours before the wings were fully expanded and functioning.
http://www.youtube.com/watch?v=4eNpWKae4RA).

The next episode will reveal what happened to the emerging adult moths…

 Stay tuned for the final episode!  

Text & Photos by Dr Wee Yeow Chin

Life History of the Yellow Palm Dart

Life History of the Yellow Palm Dart (Cephrenes trichopepla)

Butterfly Biodata:
Genus: Cephrenes Waterhouse & Lyell, 1914.
Species: trichopepla Lower, 1908
Wingspan of Adult Butterfly: 38-45mm
Caterpillar Local Host Plants: Cocos nucifera (Arecaceae; common name: Coconut), Livistona sp. (Arecaceae), Cyrtostachys renda (Arecaceae; common name: Lipstick Palm).

A female Yellow Palm Dart.

A male Yellow Palm Dart.

Physical Description of Adult Butterfly:

The adults are similar to Telicota spp.  in appearance but somewhat larger. Unlike the Telicota spp, the male lacks a stigma (a secondary sexual characteristics). Above, the wings are dark brown to black with prominent orange-yellow streaks and spots that are typical of the genera Telicota and Cephrenes (with a costal streak joining a band of 3 subapical spots in spaces 6-8, a post-discal series of spots from spaces 1b to 5, and finally  two streaks along the dorsum below vein 1b). The orange-yellow colour of the post-discal band on the forewing is contnued along the veins towards the termen.   Beneath, the wings are a deep yellow with post-discal spots matching those on the upperside. The post-discal bands on both wings occur in a darker shade of yellow against the ground colouration and  are distinctly edged with short, bold and thickened black-brown markings. There is a rather large black-brown tornal patch in the hindwing.

A female Yellow Palm Dart sunbathing with partially open wings.

A Yellow Palm Dart perching on a coconut frond in the late afternoon sun.

Field Observations of Butterfly Behaviour:

Since its recent discovery and addition to the Singapore checklist, the Yellow Palm Dart has  established itself firmly in Singapore with a moderately common status. Sightings are rather frequent and spread over many parts of Singapore, at locations such as neighbourhood parks,  certain offshore island, wastelands, park connectors and even in housing estates and business districts where its host plants (various Palm spp.) are present. The swift flying adults have been observed to visit flowers and sunbath in sunny weather.

Early Stages:

Yellow Palm Dart is known to utilize a number of Palm spp. in its down under homeland  in Australia. Locally in Singapore, it has been observed to utilize the Coconut Palm, Livistonia spp. and the Lipstick Palm as its larval hosts. Among these,  the Coconut Palm appears to be the most favoured local host plant. The caterpillars of the Yellow Palm Dart feed on the leaves of the host plant in all instars, and live in leaf shelters. As the caterpillar grows in size later through progressing instars, it will move to ever larger shelters built by joining cut leaf fragments or two adjacent leaflets.  One noteworthy point is that, unlike most other skipper caterpillars, the immature stages of the Yellow Palm Dart do not take much care in catapulting their frass pellets away from its shelter. It is a common sight that a leaf shelter for the Yellow Palm Dart houses both the caterpillar (up to the penultimate instar) and a considerable collection of frass pellets.

Host plant #1: Coconut Palm.


Host plant #2: Livistona sp.

A mating pair of the Yellow Palm Dart.

The eggs are laid singly on a leaf of the host plant, typically on the underside, or on the rachis or petiole of a leaf frond.  Each dome-shaped egg is initially  yellowish orange and appears to be smooth to the naked eyes. A closer inspection reveals numerous short, discontinuous and irregular tiny ridges running in a longitudinal direction. The micropylar sits atop in a darker shade of yellowish orange.  The eggs are rather large with a diameter of about 1.4-1.5mm.

Two views of an egg of the Yellow Palm Dart, diameter: 1.4-1.5mm.

It takes about 5 days for the egg to hatch. The egg  develops red mottled patches on the pole and roughly in an equatorial belt a day later, and then turns dark purplish red to pale brown entering the 4th day. At this point,  the dark head capsule is visible through the egg shell. Finally the egg decolorises to a whitish coloration as it enters the last day of the egg development phase. 

Two views of a developing egg of the Yellow Palm Dart, one-day old.

Two views of a near mature egg, 4-day old.

Two views of a mature egg with nibbling of egg shell commenced, 5-day old.

An animated sequence showing the egg shell being nibbled away by the caterpillar prior to its emergence through the hole made. Note the egg shell is eventually eaten by the newly hatched, sans the egg base.

The young caterpillar eats just enough of the shell to emerge, and then immediately proceeds to finish the remaining egg shell (see video clip below). The newly hatched has a length of about 3.5mm. Its pale yellowish brown body is cylindrical in shape with a small number of very short and tiny dorso-lateral  and lateral setae. There is a tuff of moderately long setae on the posterior segment.  The last 2-3 posterior segments are adorned with reddish to orangy mottled patches on the dorusm. Its head is black with a black collar lying behind it on the prothorax.

A Yellow Palm Dart caterpillar emerges from its egg.

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

After consuming the egg shell, the newly hatched caterpillar  constructs its first leaf shelter,  typically at the tip of a leaflet of the palm frond.  The body takes on a slight green undertone after a few feeding sessions on the leaf.  The 1st instar takes a total of 2-3 days to complete with body length reaching about 7mm.

Two views of a 1st instar caterpillar, late in this stage, length: 7mm.

A 1st instar caterpillar in its leaf shelter, with a collection of frass pellets nearby. Note the adjacent feeding site.

The body of the 2nd instar caterpillar resembles that of the first instar, but with the dark collar on the prothorax now absent. The tuff of long setae at the posterior end is still present together with the reddish to orangy patches on the dorsum of the posterior segment (less conspicuous).  This instar lasts a total of 3-4 days with the body length reaching up to 10-11mm.

Two views of a 2nd instar caterpillar, newly moulted, length: 7.5mm.

Two views of a 2nd instar caterpillar,  length: 9.3mm.

The 3nd instar caterpillar resembles the 2nd instar caterpillar except for a more yellowish green body colour, the absence of the red/brown markings on the dorsum of the posterior segment,  and a change in marking on the head capsule.  Whilst a minority of specimens still sport a totally black head capsule, most have two whitish patches of varying extent on both  sides of the head capsule (see picture below). This instar lasts a total of 3-4 days with the body length reaching up to 15-16mm.

Two views of a newly moulted 3rd instar caterpillar.

Two views of a 3rd instar caterpillar, length: 14mm.

Heads of four 3rd instar caterpillars, showing variation in markings.

The 4th instar caterpillar differs from the 3rd instar caterpillar in having two yellowish "cheek" patches on the head capsule, one  on either side of the mouth parts. In the head capsule, the lateral white patches elongates and enlarges to differing extent in different specimens, with some having the white patch reaching down to the yellow "check" patch (see picture below). This instar lasts 3-4 days with the body length reaching up to 26-28mm.

Two views of a 4th instar caterpillar, early in this stage,  length: 18mm.

Two views of a  4th instar caterpillar, late  this stage, length: 26.5mm.

Heads of four 4th instar caterpillars, showing variation in markings.

Again the change from the 4th instar to the 5th takes place on the head capsule with most specimens possessing a head dominated by the two large white lateral patches, with the back bands lining the epicranial suture varying in thickness (see picture below).

A newly moulted 5th instar caterpillar.

Two views of a male 5th instar caterpillar, late in this stage, length: 35mm.

The 5th instar takes about 6-7 days to complete with the body length reaching up to 39-41mm, In the last 2 days of this instar, except for the yellow-dominated dorsum,  the body takes on a strong jade green coloration changing into purplish blue in the last day. The caterpillar ceases feeding and its body shrinks to about 34mm. Next it proceeds  to seal the shelter it is in with silk threads.

Two views of a  5th instar caterpillar, late in this stage, length: 41mm.

Heads of four 5th instar caterpillars, showing variation in markings.

Two views of a 5th instar caterpillar, with body color changes prior to becoming a dormant pre-pupa, length: 34mm.

Towards the end of 5th instar, the body of the caterpillar shortens appreciably. Soon the caterpillar becomes dormant in the pupation shelter. In the tightly closed pupation shelter, the caterpillar also secretes large quantity of a whitish waxy substance. This prepupatory phase lasts for 1-1.5 days.

A pupation shelter opened to reveal  a pre-pupa of The Yellow Palm Dart.

Pupation takes place within the leaf shelter. The pupa does not have a cremastral attachment  nor a silk girdle and it is mainly secured with tightly woven silk threads in the shelter. It has a short thorax, a rather long abdomen, a short and pointed rostrum. The body is dark brown in the thorax and wing pad areas, but pale reddish brown in the abdomen. Length of pupae: 23-24mm.

Two views of a pupa of the Yellow Palm Dart, length:24mm

After 9 days, the pupa becomes mostly  golden brown with the wing pad areas in darker brown and showing the orange markings present on the forewing upperside. Eclosion takes place the next day.

Two views of a mature pupa of the Yellow Palm Dart.

A newly eclosed Yellow Palm Dart.

References:

• Oviposition and territorial behaviour in Cephrenes trichopepla and a new distribution record, Dunn K.L., Victorian Ent., 24(1), pp.21-25, 1994.
• Notes on the biology and new larval hosts of Cephrenes  - Part II, Dunn K.L., Victorian Ent. 25(1), pp.3-12, 1995.
• The Butterflies of  Australia, M. Brady, CSIRO Publishing, 2000.
• A Field Guide to the Butterflies of Singapore, Khew S K, Ink on Paper Comm. Pte. Ltd., 2010.

Text by Horace Tan, Photos by Loke PF,  Khew SK and Horace Tan

Random Gallery - Club Silverline

Random Butterfly Gallery
The Club Silverline (Spindasis syama terana)


Canon 1DMkIII + Tamron 180mm + EX580 II ; ISO640 ; 1/200s ; f/6.3 , Fill-flashed, Handheld

Photographing butterflies is a challenging pursuit, as these flying jewels are often skittish and rarely allow more than a fleeting moment for the photographer to compose, focus and press the shutter.  Spotting a butterfly perched on an isolated flower, proboscis extended and feeding, with a perfectly lit and smooth background is not easy to come by.  However, when the opportunity presents itself, the result is often a moment of exhilaration for the photographer.  Here, ButterflyCircle member Sunny Chir takes advantage of a feeding Club Silverline as it feeds on a Bidens pilosa flower, yielding a perfect pose of this small but attractive butterfly.

The Atlas Moth Chronicles - Episode 1

The Atlas Moth Chronicles

Episode 1 : The Arrival of the Moths

Rarely do we feature non-butterfly articles on this blog. But occasionally, we do make some exceptions when deserving stories such as the one on the While Bellied Sea Eagle was featured some time back.  This time around, we feature Dr Wee Yeow Chin's encounters with the largest moth in the world, the Atlas Moth (Attacus atlas).  

Dr Wee Yeow Chin is a fellow blogger and a good friend and supporter for many years.  He is a prominent botanist and popular academician who taught at the Department of Biological Sciences at the National University of Singapore until his retirement in 1997.  He was also the founding President of the Nature Society of Singapore back in 1991.  In recent years, he set up the Bird Ecology Study Group (BESG) as an alternative group to share information and document the behaviour of birds.  Today, the BESG stands as an independent group that is popular amongst bird-watchers all around the world and the blog contains a treasure trove of information par excellence in the study of birds in their natural environment. 

Dr Wee's curious mind and never-ending quest for answers extended beyond his beloved plants, then birds, and recently led him to share his observations of the ecology of the Atlas Moth.  This is his story...

Atlas Moth: 1. The arrival of the moths

A mating Atlas Moth pair on Limau Purut (Citrus hystrix)

The first time the Atlas Moth (Attacus atlas) got my attention was when about two dozens individuals were seen attached to pupal cases on my Limau Purut (Citrus hystrix) tree. I failed to notice the caterpillars when they were munching on the leaves. I failed to notice the pupae when they developed on the tree. Only when the large moths emerged from the pupa cases and hung out did I finally take notice.

 

Most of the moths were in pairs, each pair clinging together from a pupal case. I failed to question the significance of this. I was simply awed by the presence of these large moths. Seeing the silky cases, I was puzzled as to how these large moths managed to get out of the cases. The cases remained intact except of a small opening at one end but how would it be possible for such a large moth to crawl out of such a small opening? I asked around but failed to get a satisfactory answer. And every year since then, I kept watch on the tree hoping for the return of the caterpillars so that I could get an answer to the puzzle. But the tree was never infested with these caterpillars ever since.  

My next encounter with the Atlas moth was seven years later. And that encounter saw me breeding two generations of caterpillars before I finally got answers to my questions.

Discarded Atlas Moth pupa wrapped in Mahang Leaf

In December 2011 I picked up a discarded pupa wrapped round a dried blue Mahang leaf (Macaranga heyeni) on the ground below the tree in my garden. Curious as to what it was and hoping to keep it as a specimen, I left it on a bench in my porch. Imagine my surprise when a few mornings later I found a pair of large Atlas Moths clinging to the spout of a nearby upturned funnel. 

A male came in the night to mate with the newly eclosed female Atlas Moth

The body of one was larger than that of the other and the tips of their abdomens were in contact. The size difference of their wings was only slight, with the tips of the forewings narrowing to a point, each with an eyespot. The antennae of the pair were also different.

The wing tips of the Atlas Moths' wings - reminescent of a snake's head?

The smaller moth had wider antennae while the larger one narrower. I was to find out later that the female moth is larger and has narrower antennae. The male moth on the other hand is smaller but with wider antennae to enable it to detect the pheromone released by the females from some distance away.

Fascinated, I photographed the pair, moving the funnel around for better positions. The moths remained attached all the time, never attempting to fly off.

Atlas Moth eggs

The pair was then placed inside a cage where they remained attached together until the next morning when they disengaged. On the funnel were clumps of small oval eggs, each 2.5 mm long and 2 mm wide, numbering about 250. The moths were then released and the eggs transferred on to the leaves of a Limau Purut twig taken from my garden. By then I was obviously aware that this is one of the host plants of the caterpillars.

For the next six months I was totally engaged in breeding these caterpillars that was to eventually lead to the answers of my questions. I was to realise that the discarded pupa actually had a live caterpillar in its final stage of metamorphosis inside. And that the moth that emerged was actually a female. The female moth somehow crawled on to the spout of the upturned funnel where it spread its wings to dry and during the night attracted a male that flew in to copulate with it. However, the puzzle as to how the female moth emerged from the pupil case was to elude me until very much later when I finally managed to document the process after numerous failed attempts to be at the right place at the right time.

To be continued...

 
A mating pair of Atlas Moths with the female still clinging onto her pupa - shot at Pulau Ubin

Text by Dr Wee Yeow Chin : Photos by Khew SK & Wee Yeow Chin