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 post-discal white bands traversing both fore- and hindwings. On the hindwing, the post-discal band crosses and continue below vein 1a. On the forewing, the post-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:
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 post-discal white bands traversing both fore- and hindwings. On the hindwing, the post-discal band crosses and continue below vein 1a. On the forewing, the post-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.
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.
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.
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.
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.
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.
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.
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.
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.
Video: A Common Onyx emerges from its pupal case.
- [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.
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