07 October 2017

Butterfly of the Month - October 2017

Butterfly of the Month - October 2017
The Pale Mottle (Logania marmorata damis)


A Pale Mottle perches on the top of a leaf to rest

We are into the 10th month of 2017 now, and the cooler temperatures and wetter weather of the year end monsoons are upon us. Those countries in the northern hemisphere prepare for autumn and the coming of winter. A recent trip to Shanghai and Suzhou was met with heavy rain and I had experienced for the first time, what a 5-hour delay on an SIA flight was like. Probably nothing as far as flight delays are concerned, but a most unproductive day sitting on the plane and watching movies with glazed eyes.



In Singapore, the wetter weather saw a drop in butterfly activity in the majority of our favourite hunting grounds. Butterfly photography outings over the past couple of weeks were largely unproductive (besides the high chance of getting soaked in one of our tropical thunderstorms). But cooler days (and nights) were a welcome relief from the hot humid days in the earlier months of the year.




Just in the first week of October, another senseless shooting occurred in Las Vegas in the US. Despite calls for gun control, very little has been done, and how many more innocent lives must be lost before someone will say enough is enough? A gunman opened fire from a hotel overlooking a country music concert in Las Vegas, killing at least 58 people and wounding more than 489 others in the deadliest shooting in modern U.S. history.




It is quite surreal as one views the many videos that are on the internet. It is a random shooting and you wonder who a bullet finds in that crowd, and who a bullet misses. Life is fragile indeed. Singapore is fortunate to have strict gun control laws and it is highly unlikely that a mass shooting like this can happen, even though there are no guarantees that there are determined madmen around who try to beat the system and laws.



Around the region, another natural disaster in the making is the potential eruption of the Indonesian active volcano, Mount Agung in Bali. Mount Agung has reached a "critical" stage with 500 tremors shaking the area a day, according to Indonesia's National Disaster Management Agency. According to news reports, more than 134,000 people have fled the area surrounding the Mount Agung, fearing an imminent eruption. Despite the local tourism authorities assuring tourists heading for Bali that it is still "safe", it is inevitable that the tourism numbers will drop significantly as people will avoid the area.



Pale Mottles stopping to feed on the secretions of other insects amongst the ants

Again, our little island of Singapore is blessed in that we are free of typhoons, earthquakes, erupting volcanoes and other natural disasters that we often see around the world. There have been tremors felt in parts of Singapore whenever an earthquake occurs in neighbouring Indonesia, but nothing serious has affected the island in recent history.


A mating pair of Pale Mottles

Moving away from disasters, both natural and man-made, we turn our attention to our Butterfly of the Month for October 2017 - the Pale Mottle (Logania marmorata damis). This tiny butterfly belongs to the interesting sub-family of butterflies called Miletinae or collectively called the Harvesters. The caterpillars of this subfamily are considered "carnivorous", as their caterpillars feed on coccids, mealy bugs, aphids and other insects.


A typical perching Pale Mottle with its forelegs pulled in tightly to its thorax

The Pale Mottle is not considered a rare species in Singapore, as they are widespread and can occur anywhere where their caterpillar food source is available on a wide variety of plants. The adult butterfly flies with a restless erratic flight, often remaining in flight for long periods of time without stopping to rest.


A Pale Mottle feeding on the secretions of mealy bugs that are tended by ants

With a wingspan of only about 20mm, the Pale Mottle frequents shaded areas in forested localities over a wide variety of habitats. It can even be found in urban gardens and parks. As it flutters around the shrubbery, one can often expect it to land on a congregation of ants tending to aphids or other similar 'pests' that exude sweet secretions.



A Pale Mottle amongst ants - what makes the butterfly 'invisible' to these predators?

The Pale Mottle is often observed to feed on the secretions of these insects where the attending ants curiously leave the butterfly alone. Are there any natural 'cloaking devices' that the butterfly possesses that make it invisible to the ants? Or the ants instinctively know that the butterfly is not a threat and leave it alone? A good subject for a research topic!



The upperside of the Pale Mottle is a bluish grey with a broad black apical border. The hindwing is brown in the male, but features streaks of grey in the female.  The underside is cryptically marked and mottled with dark brown, buff and light orange striations, giving the butterfly a marbled appearance.



Although most encounters of this butterfly are of individuals fluttering around trees and shrubs, mating pairs of the Pale Mottle are regularly seen - as can be observed by the frequent number of photographs of a pair of the butterfly 'doing their thing'. Mating pairs are usually more docile and perch stationary, making it much easier for a photographer to shoot them.


A Pale Mottle feeds on mealy bug secretions amongst the 'farmer' ants

When they locate a colony of ants tending to aphids, mealy bugs or coccids, the Pale Mottle tends to flutter around the plant stem where the ants can be found, often landing right in the midst of the ants and aphids/mealy bugs and then joining the ants that are feeding on the secretions of these insects. At times, a female may lay her eggs beside the aphids/mealy bugs, where, upon hatching, proceed to feed on the other insects!



At other times, an individual stops to rest on a leaf tip, making it an easy subject to hunt down and photograph. However, its diminutive size makes it a challenging macro subject to shoot when trying to deal with the shallow depth of field to ensure all parts of the butterfly are in sharp focus. Its preference to rest in deep shade also makes photography in low light conditions necessary.


A not-so-common shot of a Pale Mottle with all six legs fully extended

The Pale Mottle features banded legs, black at the joints. antennae are long and curved at the tips. Species in the subfamily are also characterised by prominent palpi, projecting way beyond the head and eyes of the butterfly. Even though the species has six fully-developed legs, individuals usually perch on four legs, and hold their forelegs close to the thorax. Only on rare occasions where an individual is seen perching with all six legs fully extended.



As mentioned earlier, the caterpillars of the Pale Mottle feed on other living creatures like coccids, mealy bugs and aphids, making them carnivores, unlike most caterpillars of Lepidoptera, which largely feed only on plant material.

Text by Khew SK : Photos by James Chia, Brian Goh, Huang CJ, Khew SK, Koh CH, Loke PF, Bobby Mun, Nelson Ong, Michael Soh, Jonathan Soong, Bene Tay and Anthony Wong.

Related article : Mergers, Partnerships and Betrayals

30 September 2017

Life History of the Ganda Dart

Life History of the Ganda Dart (Potanthus ganda)


Butterfly Biodata:
Genus: Potanthus Scudder, 1872
Species: ganda Fruhstorfer, 1911
Wingspan of Adult Butterfly: 21-24mm
Caterpillar Local Host Plant: Centotheca lappacea (Poaceae, common name: Sefa).




Physical Description of Adult Butterfly:
On the upperside, the wings are dark brown with orange-yellow markings. On the hindwing, a spot is present in space 7, but usually none or a small spot in space 6. On the forewing, the postdiscal band is dislocated at vein 6, and the spot in space 3 barely overlaps with the spot in space 4. On the underside, the wings are black but heavily dusted with orange-yellow scales and adorned with orange-yellow bands as above. On both upperside and underside, the veins crossing the yellow bands in the hindwing are not, or minimally, darkened.



Field Observations of Butterfly Behaviour:
Ganda Dart is a recent addition to the Singapore Checklist and is typically found in forested ares in the nature reserves. It has a similar appearance as the more commonly found Lesser Dart (Potanthus omaha). The adults fly with the usual fast and skittish manner, and can be found sunbathing in sun-lit environments and visiting flowers for nectar in the nature reserves.



Early Stages:
Centotheca lappacea, commonly found in the nature reserves, have been recorded as the local larval host for Ganda Dart. The caterpillars of the Ganda Dart feed on leaves of the host plant, and live in shelters made by joining edges of a leaf or cut segment together with silk threads. As with other skipper species, the caterpillars have the habit of forcefully ejecting their frass pellets.

Local host plant: Centotheca lappacea.

The eggs are typically laid singly on the underside of a leaf of the host plant. Occasionally eggs can also be found on the upperside and near the leaf base. Each dome-shaped egg is whitish-yellow with numerous, fine longitudinal straitions. The base diameter is about 0.85mm with a height of about 0.75mm.

Two views of an egg of the Ganda Dart.

Two views of a maturing egg of the Ganda Dart.

It takes about 4.5-5 days for the egg to hatch. The young caterpillar eats just enough of the shell to emerge, and will devour the rest of the egg shell after emergence. The newly hatched has a length of about 2mm. Its whitish body has a tuff of long setae at the posterior end. The head capsule is entirely black and there is a black collar just behind the head on the dorsum of the prothorax.

Two views of a newly hatched caterpillar of the Ganda Dart.

A newly hatched caterpillar of the Ganda Dart, in the midst of constructing its first leaf shelter at the leaf tip.

The newly hatched constructs its leaf shelter at the leaf tip soon after it is done with the egg shell. The body color changes to pale yellowish green after a few feeding sessions on the leaf. The 1st instar takes about 5 days to complete with body length increases to about 4mm.

Two views of a 1st instar caterpillar, length: 3.3mm.

Two views of a late 1st instar caterpillar, dormant prior to its moult, length: 3.8mm.

Leaf shelter of an early instar caterpillar of the Ganda Dart.

The 2nd instar caterpillar is yellowish green with a black head capsule. The black prothoracic collar is still present. This instar lasts about 5-6 days with the body length reaching about 7-7.5mm.

Two views of a 2nd instar caterpillar, newly moulted.

Two views of a 2nd instar caterpillar, length: 5.5mm.

Two views of a late 2nd instar caterpillar, dormant prior to its moult, length: 7mm.

The 3nd instar caterpillar resembles the 2nd instar caterpillar closely but with its anal plate turning brown to black in most specimens. This instar lasts about 5-6 days with the body length reaching about 11-12mm.

Two views of a 3rd instar caterpillar, length: 8.5mm.

Two views of a 3rd instar caterpillar, length: 10.8mm.

Two views of a late 3rd instar caterpillar, dormant prior to its moult, length: 10.5mm.

The 4th instar caterpillar bears a strong resemblance to the 3rd instar caterpillar but with the anal plate now broad and dominantly black. This penultimate instar lasts about 5-6 days with the body length reaching up to 17-18mm.

Two views of a 4th instar caterpillar, newly moulted.

Two views of a 4th instar caterpillar, length: 17mm.

Two views of a late 4th instar caterpillar, dormant prior to its moult, length: 17.5mm.

The 5th instar ushers in a drastic change in the appearance of the head capsule. It is dark brown along frontal cleavage lines and the periphery, but whitish coloration fills in the area between the two. The body is pale yellowish green, and the anal plate not longer as in the previous instar. This final instar takes about 7-8 days to complete with the body length reaching up to about 31-33mm.

A newly moulted 5th instar caterpillar of the Ganda Dart.

Two views of a 5th instar caterpillar, length: 33mm.

Two views of another 5th instar caterpillar, late in this stage, length: 26.5mm.

Towards the end of the 5th instar, the body of the caterpillar shortens and its coloration changes uniformly to whitish-yellow. Typically the basal part of the leaf is devoured bare of any lamina and the pupation shelter is constructed by folding and sealing the remaining part of the leaf blade. Within the shelter, it spins a silk pad to secure itself. Whitish waxy substance is deposited on the inner wall of the shelter in moderately large quantity. It stays dormant in the prepupatory phase which lasts for about 1 day.

A pre-pupatory larva of the Ganda Dart.

A pupation shelter of the Ganda Dart.

The pupa is secured within the tight confine of the pupation shelter. Its long, slender body is mostly pale yellowish brown and coated with the white waxy substance. There are two rather large, reddish brown "eye" markings at the anterior end. Length of pupae: 15.5-18mm.

Two views of a pupa of the Ganda Dart.

On the last day of the pupal period, the pupa becomes mostly dark brown to black. The next day, after about 9 days of the pupal phase, eclosion takes place with the adult emerging from the pupal case.

Two views of a mature pupa of the Ganda Dart.

A newly eclosed Ganda Dart.

References:
  • [C&P4] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society, 1992.
  • Butterflies of Thailand, Pisuth Ek-Amnuay, 2nd Edition, 2012.
  • A Field Guide to the Butterflies of Singapore, Khew S.K., Ink On Paper Communications, 2010.
Text by Horace Tan, Photos by Koh Cher Hern, Khew SK  and Horace Tan