Butterfly of the Month - July 2021

Butterfly of the Month - July 2021

The Common Sailor (Neptis hylas papaja)

A Common Sailor feeding on the ripened fruit of the Singapore Rhododendron (Melastoma malabathricum)

We are well into the 2nd half of 2021, as the world is beginning to reach a limit with pandemic fatigue. Some governments are beginning to consider treating the virus as "endemic" and living with it will be what we may have to contend with, in the near future. After all, how many more lockdowns, quarantines and movement restrictions can the populace take?

A Common Sailor perched with its wings opened flat to sunbathe.  Note the metallic green sheen on its thorax when viewed from above.

As vaccination programmes reach a certain critical number, some jurisdictions are planning to relax various restrictive measures. For example, face-masks may be dispensed with, or movement controls and safe distancing relaxed when a benchmark percentage of the population has been fully vaccinated. The many restrictions, safety measures and movement controls have already taken their toll on many economies all around the world , with some companies facing imminent and permanent closure.

Over in Tokyo, the Japanese government appeared to have taken the COVID19 bull by the horns and decided to proceed with the "2020" Tokyo Olympics in 2021. Perhaps the motivation behind the decision to proceed to hold the Olympic games could be economic rather than prudence. But here it is, the Games have begun, but with most spectators watching online and stadiums and games venues largely empty. However that does not take away the glory from the athletes who achieve the podium positions in their respective sports.

Back home in Singapore, the resurgence of the Delta variant in KTV lounges sparked off another round of restrictions in the community. This was followed by several other clusters emerging from a wholesale centre, which then moved to public wet markets. In just a few days, the numbers of new infections hit three-digits and disrupted the progress of opening up. Dining out in public places is no longer allowed until mid-August as the government rushes to vaccinate the population.

A classic pose of the Common Sailor perched on a blade of lallang

Already the Singapore government is debating on the possibility of "opening" up and living with the virus as if it were just the common influenza. Data collected and findings that show that fully vaccinated infected individuals have mild symptoms or even asymptomatic, has given optimism that it may one day be possible to take COVID19 in our stride as an endemic disease that is no longer life-threatening. We look forward to that day!

Our feature butterfly for July 2021 is the Common Sailor (Neptis hylas papaja). This butterfly is one of the four Sailor species found in Singapore - three from the genus Neptis, and one from Phaedyma. The Common Sailor is one of the black-and-white lookalikes and sometimes confused with the Burmese Sailor or Short Banded Sailor. However, when the butterfly is at rest, there are distinguishing characteristics in the markings that will separate the lookalikes.

The Common Sailor has a distinctive weak flap-glide-flap flight that separates it from the related but similar looking Sergeants (Athyma spp) that have a more powerful and robust flight. The Common Sailor is widely distributed in Singapore, being found in urban parks and gardens as well as the forested nature reserves and our offshore islands.

The species has a black and white striped upperside. The forewing white cell streak is usually interrupted by a thin black line towards the cell end. The underside of both wings is a rich golden brown. The white stripes are distinctly outlined in black and this is one of the distinguishing attributes of this species to separate this species from its lookalike cousins.

A mating pair of Common Sailors

The eyes of the Common Sailor are transparent and the compound eyes are bluish grey.  On the upperside of the thorax, there is an iridescent greenish-blue sheen. Its abdomen is not white-ringed next to the white discal band on the hindwing.  Its antennae clubs are usually orange-yellow tipped.

A Common Sailor feeding on the ripened fruit of the Singapore Rhododendron (Melastoma malabathricum)

The caterpillars of the Common Sailor feed on a variety of host plants, all from the Fabaceae family. The local host plants on which the species has been successfully bred are : Calopogonium mucunoides, Canavalia cathartica, Aeschynomene americana, Senna alata, Psophocarpus tetragonolobus and Centrosema molle.

Text by Khew SK : Photos by Khew SK, Loh MY, Tan BJ and Anthony Wong

Life History of the Silver Forget-me-not

Life History of the Silver Forget-Me-Not (Catochrysops panormus exiguus)

Butterfly Biodata:
Genus: Catochrysops Boisduval, 1832
Species: panormus C. Felder, 1860
Subspecies: exiguus Distant, 1886
Wingspan of Adult Butterfly: 24-30mm
Caterpillar Local Host Plants: Dendrolobium umbellatum (Fabaceae, common names: Dendulang, Petai Belalang, Petai Laut, Sea Dendrolobium, 伞花假木豆), Pueraria phaseoloides (Fabaceae, common names: Puero, Tropical Kudzu).

A Silver Forget-me-not visting flowers for nectar.

The upperside of a male Silver Forget-me-not.

A main identification key of the Silver Forget-me-not.

Physical Description of Adult Butterfly:
On the upperside, the male is pale shining blue on both forewing and hindwing, and a black marginal spot in space 2 of the hindwing; the female is heavily black dusted with broad black apical area on the forewing, pale bluish wing bases, and the black marginal spot is orange-crowned. On the underside, both sexes are greyish white with the usual streaks and spots. In the hindwing, there is a long filamentous white-tipped black tail at vein 2 and an orange-crowned black spot in space 2. In the forewing, there is a small costal spot which is placed close to the upper end of the postl-discal streak (see picture above).

The upperside of a female Silver Forget-me-not.

A female Silver Forget-me-not taking nectar from a flower of Cuphea hyssophifolia 'Pink' (False Heather).

A male Silver Forget-me-not perching on a stem of Dendrolobium umbellatum.

A male Silver Forget-me-not puddling on wet ground.

Field Observations:
The Silver Forget-me-not is moderately rare in Singapore. In the past, the adults were mainly found in open wastelands. However, with the widespread planting of its host plant, Dendrolobium umbellatum, in various parks and gardens, and along several stretches of road in the recent years, adults sightings have become more frequent. At times, several individuals can be seen fighting for the favorite sunbathing spots at some of these locations. The adults fly with an erratic flight, and have been sighted taking nectar at flowering plants. Both sexes have been observed to sunbathe with partly or fully opened wings in sunlit spots. Males also have a habit of puddling on damp footpaths and wet grounds.

A female Silver Forget-me-not taking nectar from a flower of Tridax procumbens (Coat Buttons).

A puddling male Silver Forget-me-not.

A male Silver Forget-me-not found probing a leaf surface with its proboscis.

Early Stages:
In Singapore, thus far only two larval host plants have been identified. One of them is Pueraria phaseoloides, a twiner and creeping plant commonly found in open wastelands. The other plant is Dendrolobium umbellatum, a shrub or small tree usually found along seashores and in beach forests, but widespread cultivation of this plant has made it a common sight in various gardens, parks and other urban settings. On the host plants, the early stages of the Silver Forget-me-not feed on the flower buds, flowers and developing fruits, with a strong preference for flower buds.

Local host plant #1: Dendrolobium umbellatum (Fabaceae, common names: Dendulang, Petai Belalang, Petai Laut, Sea Dendrolobium, 伞花假木豆).

Local host plant #2: Pueraria phaseoloides (Fabaceae, common names: Puero, Tropical Kudzu).

A mating pair of Silver Forget-me-not.

Eggs are laid either singly or in a pair in space between tightly arranged flower buds of the host plant, and are concealed with a transparent gelatinous substance. At times, the egg might be exposed when the growth of flower buds causes them to move further apart. Each bun-shaped egg is about 0.4 to 0.5mm in diameter and whitish in color. It is bun-shaped with a depressed micropylar at the pole and a surface reticulated with rather large polygonal depressions.

A Silver Forget-me-not female searching for a spot to lay egg on Dendrolobium umbellatum.

A Silver Forget-me-not female laying an egg on Pueraria phaseoloides.

A freshly laid egg of the Silver Forget-me-not among the flower buds of Dendrolobium umbellatum. Concealed within a transparent gelatinous substance indicated by the arrow.

An egg of the Silver Forget-me-not.

Left: A fully developed egg. Right: The newly hatched caterpillar resting next to the empty egg shell.

It takes about 3 days for the egg to hatch. The young caterpillar consumes just enough of the egg shell to emerge. It is pale greyish brown in coloration, and has a length of about 1mm. Long setae (hairs) run along the length of the body dorsally as well as sub-spiracularly. The head capsule is dark brown to black in coloration. The 1st instar lasts about 3 days with the body length increased to about 1.6mm.

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

A 1st instar caterpillar feeding on a flower bud of Dendrolobium umbellatum. Note that pile of frass pellets near the posterior end of the caterpillar.

Two views of a 1st instar caterpillar, length: 1.6mm.

A late 1st instar caterpillar of the Silver Forget-me-not, dormant prior to the moult to the next instar.

In the 2nd instar caterpillar, in addition to the long setae running along the length of the body dorsally and sub-spiracularly, numerous short setae cover the body surface. The body base colour is pale yellowish green. Pale whitish dorsal bands gradually becomes distinguishable as the second instar progresses. Sub-spiracularly, the body rim is pale whitish. The head capsule remains dark brown to black in coloration, and will be so for the next two instars. The 2nd instar lasts for about 2-3 days, with the body length reaching up to 3.5mm.

Two views of a newly moulted 2nd instar caterpillar, with its old skin next to its posterior end.

Two views of a 2nd instar caterpillar of the Silver Forget-me-not, length: 3mm.

A 2nd instar caterpillar of the Silver Forget-me-not feeding on a flower bud of Dendrolobium umbellatum.

Two views of a 2nd instar caterpillar, late in this stage, dormant prior to its moult.

In the 3rd instar, the dorsal and sub-spiracular setae appears to be proportionately shorter compared to those in the previous instar. The body is now covered in a dense coat of whitish stellate setae, and the pale whitish dorsal and sub-spiracular bands are more prominent. From the outer sides of the dorsal bands, short bands emanates at the angle, giving an appearance of multiple chevron markings. The body base color ranges from pale yellow green to pale green. The dorsal nectary organ on the 7th abdominal segment is present and barely discernible.

Top: late 2nd instar caterpillar; bottom: newly moulted to 3rd instar, its old skin lying at the posterior end.

Two views of an early 3rd instar caterpillar feeding on a flower bud, length: 4.1mm.

Two views of a 3rd instar caterpillar, length: 5mm.

A 3rd instar caterpillar found in the field feeding on a seed pod of Dendrolobium umbellatum.

Two views of a late 3rd instar caterpillar on the underside of a leaf, dormant prior to its moult to the next instar, length: 5.3mm.

As the body grows to a length of around 6mm, the caterpillar stops feeding and comes to rest at a spot on the underside of a leave or stem to prepare for the next moult. After about 2-3 days in the 3rd instar, the moult to the 4th and final instar takes place.

Two views of a very late 3rd instar caterpillar, dormant prior to its moult to the final instar.

The 4th instar caterpillar resembles the 3rd instar caterpillar in most body features/markings, but with much contrasting whitish dorsal bands, chevron markings and sub-spiracular band. Thhe dorsal nectary organ on the dorsum of the 7th abdomina segment is now easily discernible, and so is the pair of tentacular organs on the 8th abdominal segment. This 4th (and final) instar lasts about 3-4 days with the body length reaching up to 11mm. On the last day of the 4th instar, the body colour of some individual caterpillars turn reddish brown (red form), while others remains greenish (green form).

Two views of a newly moulted 4th instar caterpillar (the same individual featured in the above picture).

Frontal view of a 4th instar caterpillar, showing the dark brown head.

A 4th instar caterpillar found in the field feeding on a flower of Dendrolobium umbellatum.

Two views of a 4th instar caterpillar, length: 9mm.

A 4th instar caterpillar found in the field with ants in attendance.

Two views of a late 4th instar caterpillar, red form.

As it enters the pre-pupatory phase of its life cycle, the caterpillar ceases its feeding activity. At this time, its body gradually shrinks in length. The pre-pupatory caterpillar typically settles for a spot on a surface which is partially concealed either among foliage of the host plant or in leaf litter. At the chosen pupation site, it spins a silk girdle and a silk pad to which it attaches with claspers at its posterior end.

Two views of a pre-pupa of the Silver Forget-me-not, red form.

Two views of a pre-pupa of the Silver Forget-me-not, green form.


The pupation event for a Silver Forget-me-not caterpillar.

After about 1 day of the immobile pre-pupatory stage, pupation takes place. The pupa is held firmly via its cremaster to the silk pad. It is 7 to 8mm in length, with the typical shape for a lycaenid pupa. The fresh pupa is either yellow green or pale beige brown, but it will eventually turn pale yellowish to beige brown within first day. The pupa is adorned with multiple black markings of varying sizes and shapes.

Two views of a newly formed pupa of the Silver Forget-me-not from the red-form pre-pupa.

Two views of a newly formed pupa of the Silver Forget-me-not from the green form pre-pupa.

Two views of a pupa of the Silver Forget-me-not, length: 7mm.

Two views of a mature pupa of a female Silver Forget-me-not.

Two views of a mature pupa of a male Silver Forget-me-not.

About six days later, the pupa becomes darkened in color signaling the imminent emergence of the adult. One can now tell the sex of the soon-to-emerge adult stage from the coloration of the wing pad at this stage (see pictures above). The next day the adult Silver Forget-me-not emerges from the mature pupa.


A male Silver Forget-me-not emerges from its pupal case.


A female Silver Forget-me-not emerges from its pupal case.

A newly eclosed male Silver Forget-me-not resting next to its pupal case.

References:

• [C&P5] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, G. and N.  van der Poorten (Eds.), 5th Edition, Malayan Nature Society, 2020.
• Butterflies of Thailand, Pisuth Ek-Amnuay, 2nd Edition, 2012.
• A Field Guide to the Butterflies of Singapore, Khew S.K., Ink On Paper Communications, 2nd Edition, 2015.

Text by Horace Tan; Photos by Loh Mei Yee, Lim Cheng Ai, Sunny Chir, Nelson Ong, Khew SK and Horace Tan; Videos by Loh Mei Yee and Horace Tan.