05 February 2023

Life History of the Common Onyx

Life History of the Common Onyx (Horaga onyx sardonyx)


Butterfly Biodata:
Genus: Horaga Moore, 1881
Species: onyx Moore, 1858
Subspecies: sardonyx Fruhstorfer, 1914
Wingspan of Adult Butterfly: 23-26 mm
Caterpillar Local Host Plants: Adenanthera pavonina [Fabaceae (Leguminosae), common name: Saga], Guioa pubersens (Sapindaceae).





Physical Description of Adult Butterfly:
On the upperside, the male is bright purplish blue with a broad black border on the forewing with a white discal patch not crossed by dark-dusted veins. The female is pale purplish blue and has a larger white discal patch. On the underside, both sexes are yellowish-brown with broad discal white bands traversing both fore- and hindwings. On the hindwing, the discal band crosses and continue below vein 1a. On the forewing, the discal band is notched. Both sexes have three filamentous tails on each hindwing, at veins 1b, 2 and 3, with the one at vein 2 longest among the three.



Field Observations:
The Common Onyx is rare in Singapore, and sightings have so far been restricted to the Southern Ridges and Pulau Ubin. It has a strong rapid flight, and is often observed to sunbathe at its favourite perches.

Early Stages:
Thus far, two larval host plants have been identified in Singapore. They are Adenanthera pavonina (Saga) and Guioa pubersens. The caterpillars of the Common Onyx feed on the young leaves of both plants, and on the flower buds and flowers of Saga.

Local host plant 1: Adenanthera pavonina (Saga)

Local host plant 2: Guioa pubersens.

Eggs are laids singly on the young shoot or the inflorescence of the host plant. Each egg resembles a bun with coarse hexagonal reticulations. It is initially pale greenish when newly laid but turns whitish as it matures. Each egg has a basal diameter of about 0.8mm.

Two views of an egg of the Common Onyx.

Left: ready to emerge. Right: out of the egg shell.

The egg takes about 3 days to hatch. The caterpillar nibbles away the top part of the egg shell to emerge. The newly hatched is about 1mm long, with a pale yellowish brown head and a pale yellowish brown body covered with long setae dorsally and laterally. The basal part of the dorsal setae on the metathorax and 1st to the 7th abdominal segments is marked in reddish brown. As growth progresses, dorsal tubercles on the metathorax (a pair) and 1st to 7th abdominal segments (one each) become prominently marked in dark reddish brown. The first instar sees the body length reaches up to 2.5mm, and lasts about 2.5 days before the moult to the next instar.

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

Two views of a first instar caterpillar of the Common Onyx, length: 2mm.

Two views of a late first instar caterpillar of the Common Onyx, dormant prior to its moult, length: 2.5mm.

The second instar caterpiller is pale yellowish green in base colour. It features numerous short setae on the body surface and has a number of prominent and pointed tubercles projecting from the body surface. On the mesothorax, there are 2 short dorso-lateral tubercles. On the metathorax, there are two long dark red tipped dorso-lateral tubercles. On each of the 1st, 2nd, 4th and 5th abdominal segments, there is one long dark reddish dorsal tubercle, with those on the 2nd and 5th segments longer than those on the other two segments. On the 3rd abdominal segment, there is a short reddish dorsal tubercle. On the 2nd abdominal segment, there is a short sub-spiracular tubercle on both sides of the body. There is also a pair of such sub-spiracular tubercles on the 7th abdominal segment, but longer than those on the 2nd abdominal segment. The 2nd instar lasts about 2-2.5 days with the body length reaches up to 4.2-4.9mm.

Two views of a second instar caterpillar of the Common Onyx, length: 3mm.

Two views of a second instar caterpillar of the Common Onyx, length: 4mm.

Two views of a second instar caterpillar of the Common Onyx, dormant prior to its moult, length: 4.8mm.

The third instar caterpiller has the same configuration of dorsal, dorso-lateral and sub-spiracular tubles as in the 2nd instar, but they are now proportionately longer and prominent, particuarly so for the ones on 2nd, 6th and 7th abdominal segments. Whitish patches adorn the basal part of the dorsal tubercles. A whitish band also run sub-spiracularly along the side of the body. The third instar lasts about 2-2.5 days and has its length reaches up to about 8-8.5mm before the moult to the 4th (and last) instar.

Two views of a third instar caterpillar of the Common Onyx, early in this instar, length: 5.4mm.

Two views of a third instar caterpillar of the Common Onyx, length: 8.5mm.

Two views of a third instar caterpillar of the Common Onyx, dormant prior to its moult, length: 8mm.

The 4th instar caterpillar has proportinately longer dorsal, dorso-lateral and sub-spiracular tubecles then those seen in the 3rd instar. Laterally, the lateral part of the 1st, 3rd, 4th and 5th abdominal segments are suffused with reddish brown to varying extent.

Two views of a 4th instar caterpillar of the Common Onyx, early in this instar, length: 9.5mm.

Two views of a 4th instar caterpillar of the Common Onyx, length: 14mm.

Two views of a 4th instar caterpillar of the Common Onyx, length: 16.5mm.

The 4th instar lasts about 3.5-4 days with the body length reaches up to 16.5-17mm. On the last day, the body gradually shortens. The caterpillar stops feeding, wanders around and eventually comes to rest on a spot on the stem where it begins the silk spinning effort to turn it into its pupation site. Once the silk pad is done, the caterpillar secures itself to it and turns into an immobile pre-pupa.

Two views of a pre-pupa of the Common Onyx.

The pre-pupal stage of the caterpillar lasts about one day. The ensuing pupation event turns it into a yellowh green pupa with the typical shape of a lycaenid pupa. The small pupa is about 9mm in length. The pupa attaches itself to the stem via its broad cremaster end. The pupal surface is mostly smooth, with only a few short protrusions appearing on the dorsum in several abdominal segments. There is a pair of small reddish dorso-lateral patches on the 1st abdominal segment, and U-shaped whitish markings overlayed with reddish brown patches on the 3rd to 5th abdominal segments. Small irregularly shaped whitish patches also occur on the pupal surface and in appreciable concentration on the fronter part of the wing pads.

Two views of a pupa of the Common Onyx, length: 9mm.

After six days, the pupa gradually turn dark towards the end of the day, with the wing pads prominently black with a few small whitish patches embedded. Next morning, the adult butterfly emerges from the mature pupa. It rests on the pupal case or nearby stem surface to have its wings gradually expanded. A few hours later, the adult Common Onyx takes its first flight.

Three views of a maturing pupa of the Common Onyx, from night before (Left) to the morning of eclosion (Right).


Video: A Common Onyx emerges from its pupal case.

A newly eclosed Common Onyx resting on 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 Gavin Gareth Chan, Loh Mei Yee and Horace Tan, Video by Horace Tan.

29 January 2023

Butterfly of the Month - January 2023

Butterfly of the Month - January 2023
The Autumn Leaf (Doleschallia bisaltide)

An Autumn Leaf ssp ? bisaltide var feeding at the yellow cultivar of Lantana camara

We continue with our Butterfly of the Month (BOTM) series into its 16th year featuring our local butterfly species extant in Singapore. Starting with this new 2023 series, will be a side discussion on the twelve astrological zodiac signs for each month of the year till December 2023. The astrological signs are Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.


Astrology is a pseudoscience. There appears to be no scientific validity or substantiation of the theoretical basis and verification of claims or conclusions of the characteristics of human behaviour or traits that are associated with each zodiac sign. More plausible explanations for the apparent correlation between personality traits and birth months exist, such as the influence of seasonal birth in humans.


The Western zodiac originated in Babylonian astrology, and was later influenced by the Hellenistic culture. Each sign was named after a constellation the sun annually moved through while crossing the sky. This observation is emphasized in the simplified and popular sun sign astrology. Astrology (i.e. a system of omina based on celestial appearances) was developed in Hindu, Chinese and Tibetan cultures as well - each with its own interpretation, measuring and dividing the sky are currently used by their respective differing systems of astrology.


We start with the zodiac sign Capricorn (or Capricornus). Its name is Latin for "horned goat" "having horns like a goat's", and it is commonly represented in the form of a sea goat: a mythical creature that is half goat, half fish, with the head of a goat and the tail of a fish. In astrology, Capricorn is considered an earth sign, negative sign, and is said to be ruled by the planet Saturn.

An Autumn Leaf ssp ? bisaltide var feeding on the flower of Syzygium sp.

Capricorn is the tenth astrological sign in the zodiac. People born between and including December 21 to January 19 belong to this zodiac sign. It is symbolized using the animal ‘goat’ and describes those people who are built for hard work. They are very disciplined, law-abiding and are good managers especially of themselves. They are perfectionists guided by logic and loyal and dependable. However, they are likely to tire themselves out at some point and they can also be rigid and sometimes viewed as obstinate.


Our first Butterfly of the Month for the year 2023 is the Autumn Leaf (Doleschallia bisaltide). The Autumn Leaf occurs in two different subspecies in Singapore, ssp ?bisaltide var.and ssp pratipa. The dominant subspecies, first discovered in Singapore in the early 2000's, is the more common taxon in Singapore, and has moved northwards as far as Selangor in West Malaysia. The peninsular Malaysian subspecies pratipa was last reliably recorded at the Mandai Zoo where an ovipositing female was observed in the wild and the eggs bred to adulthood.

Autumn Leaf ssp pratipa ovipositing on one of its caterpillar host plants at the Mandai Zoo
Caterpillar of Autumn Leaf ssp pratipa
Female Autumn Leaf ssp ?bisaltide var.
Caterpillar of Autumn Leaf ssp ?bisaltide var.

Although the dominant subspecies in Singapore differs from ssp pratipa in having five small white spots on the black apex of the forewing above, it is difficult to separate the two subspecies in the field.  However, their caterpillars show significant difference in the orange-red spots at the base of the lateral scoli in ssp ?bisaltide var. and are absent in ssp pratipa.

Top : Upperside of Autumn Leaf ssp pratipa  Bottom : Underside of Autumn Leaf ssp ?bisaltide var
Top : Upperside of Autumn Leaf ssp. ? bisaltide var.  Bottom : Underside of Autumn Leaf ssp. ? bisaltide var

The upperside of the Autumn Leaf is orange-brown with the forewing apex broadly blackened. The subspecies ?bisaltide var. features the prominent five small subapical white spots on the forewing above, which is absent in subspecies pratipa. The underside is highly variable with the ground colour ranging from greyish-brown to mauve-brown. The patterns on the underside are so variable that it is not easy to find two specimens which are completely identical markings.

Underside of a male Autumn Leaf ssp ?bisaltide var

Males of the subspecies ?bisaltide var. feature large prominent white spots on the underside of both wings, whilst females are generally more orange-brown with less distinct markings. The leaf-like pattern of the underside of the Autumn Leaf is an excellent camouflage. The tornus of the hindwing is produced to a tail, resembling a leaf stalk, and when the butterfly is at rest with closed wings amongst dead foliage, it is hard to spot.

Upperside of a male Autumn Leaf ssp ? bisaltide var puddling at a sandy streambank

The Autumn Leaf has a strong flight, and is usually skittish and hard to approach. However, it is often observed feeding at flowers. Males are also regularly seen puddling at muddy footpaths and damp sandbanks where they can be approached for a closer look. As with most species of the Nymphalidae family, the forelegs are underdeveloped and the butterfly perches on the mid- and hind legs.

Underside of a male Autumn Leaf ssp pratipa

The caterpillars of both subspecies feed on a variety of host plants, ranging from Asystasia gangetica (Acanthaceae), Pseuderanthemum laxiflorum (Acanthaceae), Pseuderanthemum carruthersii var. reticulatum (Acanthaceae), and is likely to feed on other host plants in the Acanthaceae family as well. The status of the two subspecies is a good potential for further taxonomic and genetic research to establish with greater clarity in future.

Text by Khew SK : Photos by Khew SK, Loh MY, Loke PF, Horace Tan and Anthony Wong

31 December 2022

Butterfly of the Month - December 2022

Butterfly of the Month - December 2022
The Barred Line Blue (Prosotas aluta nanda)

A Barred Line Blue on tiptoe puddling at a sandy streambank in the nature reserves of Singapore

December and Christmas Day 2022 have come and gone, and we are in the final hours of a tumultuous year that is probably best remembered for its unprecedented upheavals in world events. For most countries, 2022, the third year of the Covid19 pandemic, was all about opening up, living with Covid and dealing with other more pressing livelihood issues like inflation, rising rents and interest rates and escalating costs of daily essentials.


Countries like Ukraine had to face the spectre of war sufferings and the painful uncertainty of when life would go back to a peaceful existence without the fear of getting one's home bombed out. After almost a year, it would appear that the war will continue, despite efforts for peaceful negotiations and sanctions imposed on Russia. It is likely that hostilities will continue into 2023 with neither side willing to call a truce. And human lives will continue to be sacrificed in the name of sovereignty.


China's Zero-Covid management began to crack under the pressure of public protests and the prospects of further damage to their already battered economy in the coming year. A much-awaited announcement of opening up and removing quarantine requirements lent some cheer and optimism to the Chinese in late December. It is probably the last large economy to announce that it was finally willing to "live with Covid" and get on with life, like the rest of the world had already done so for most part of 2022.


For soccer fans around the world, World Cup 2022 in Qatar was a nice distraction from the daily dose of news of unhappy happenings all around the world. This must be the first time the World Cup had to be held at this time of the year instead of during the summer months. In the harsh climate of the Arab world which comprises mainly low-lying deserts, it would have been unbearable to hold the matches in the scorching summer temperatures that exceed 40 degC. Argentina were crowned the champions after winning the final against the title holder France 4–2 on penalties following a 3–3 draw after extra time.


Our Butterfly of the Month for December 2022, and to close out the year, is the recently-discovered Lycaenidae - The Barred Line Blue (Prosotas aluta nanda). Records show that the earliest photographed individual of this species in Singapore dates back to Feb 2008. However, it was not validated until more sightings and photographic records of this species were available in recent years. The Barred Line Blue was not listed in the checklists of the early reference authors and hence recorded as a "non-native" species.


With its non-remarkable grey undersides and white striae, the Barred Line Blue may have been missed or mistaken as one of the lookalike Nacaduba cousins that are extant in Singapore. Its resemblance to several of the more common Six Line Blues may have caused it to be missed by the early authors. This species has been more often encountered puddling at muddy streambanks than at flowering plants. Females are presumably much rarer.


The male Barred Line Blue is blue on the upperside whilst the female has wide brown borders with a pale bluish-green patch on the forewing. The eyes are jet-black and opaque and the eyes and palpi are particularly hairy. The body of the antennae are black-and-white, with the clubbed end of each antennae white tipped.


The diagnostic feature of the Barred Line Blue is the post-discal striae in space 3 of the forewing below. This striae is shifted slightly towards the base of the wing compared to its adjacent striae in spaces 2 and 4. The hindwing has a black white-tipped filamentous tail emerging from vein 2. The orange-crowned black tornal spot on the hindwing is large and prominent.


The Barred Line Blue has a quick erratic flight and is usually skittish, as is the case with the other species in the Prosotas and Nacaduba genera. Thus far, most of the sightings of this species have been in the forested nature reserves, and more often, males are encountered puddling at sandy streambanks on hot sunny days, usually attracted to decomposing animal matter or excretions. Other sightings are of the butterfly feeding on flowering plants at the edges or within the forested nature reserves.

On this final day of 2022, I would like to wish all our readers from all over the world a Happy New Year 2023 and May all your Butterfly Wishes come true in the year ahead! 

Text by Khew SK : Photos by Huang CJ, Khew SK, Koh CH, Loh MY, Loke PF, Low JK, Aaron Soh, Zick Soh and Mark Wong