Life History of the Brown Onyx

Life History of the Brown Onyx (Horaga albimacula albistigmata)

Butterfly Biodata:
Genus: Horaga Moore, 1881
Species: albimacula Wood-Mason & de Nicéville, 1881
Subspecies: albistigmata Moulton, 1912
Wingspan of Adult Butterfly: 10.5-11.5 mm
Caterpillar Local Host Plant: Adenanthera pavonina (Fabaceae, common name: Saga).

Physical Description of Adult Butterfly:
On the upperside, both sexes are brown with the white spot on the forewing not extending below vein 2. Both sexess have blue scales in the basal area. On the underside, both sexes are yellowish-brown with a dark post-discal line present on both fore- and hindwings, outwardly edged whitish. In the forewing, the edging forms a broad white band which does not go above vein 6. Both sexes have three filamentous tails on the hindwing, at veins 1b, 2 and 3, with the one at vein 2 longest among the three. The hindwing also has two black tornal spots and metallic green scaling in the tornal area.

Field Observations:
The Brown Onyx is rare in Singapore. A handful of recent sightings of the early stages have so far been restricted to the Southern Ridges.

Early Stages:
Only one larval host plant, Adenanthera pavonina (Saga), has been identified in Singapore. Just like the Common Onyx, caterpillars of the Brown Onyx feed on young leaves of Saga. In all four instars, the caterpillars of the Brown Onyx closely resembles those of the Common Onyx, and it is impossible to tell them apart in the field.

Local host plant: Adenanthera pavonina (Saga)

Eggs are laids singly on the young shoot 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 Brown Onyx.

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 the abdomen is marked in reddish brown. As growth progresses, dorsal tubercles on the metathorax (a pair) and 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 2.5-3 days before the moult to the next instar.

Two views of an early 1st instar caterpillar of the Brown Onyx, length: 1.3mm.

Two views of a first instar caterpillar of the Brown Onyx, late in this instar, 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-6th abdominal segments, there is one long dark reddish dorsal tubercle, with those on the 2nd and 6th segments longer than those on the other two segments, and the one on the 3rd segment being the shortest. 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 2.5-3 days with the body length reaches up to 4.7-4.9mm.

Two views of a second instar caterpillar of the Brown Onyx, early in this stage, length: 2.5mm.

Two views of a second instar caterpillar of the Brown Onyx, length: 4.1mm.

Two views of a second instar caterpillar of the Brown Onyx, dormant prior to its moult, length: 4.6mm.

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. 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 3 days and the body length reaches up to about 8.1-8.3mm before the moult to the 4th (and last) instar.

Two views of a third instar caterpillar of the Brown Onyx, early in this instar, length: 4.9mm.

Two views of a third instar caterpillar of the Brown Onyx, length: 7mm.

Two views of a third instar caterpillar of the Brown 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 Brown Onyx, early in this instar, length: 8.3mm.

Two views of a 4th instar caterpillar of the Brown Onyx, length: 12.5mm.

Two views of a 4th instar caterpillar of the Brown Onyx, late in this stage, length: 14mm.

The 4th instar lasts about 3.5-4 days with the body length reaches up to 14.0-14.2mm. 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 Brown 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 8mm 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 Brown Onyx, length: 8mm.

After six days, the pupa gradually turn dark towards the end of the day, with the wing pads prominently black with a small whitish and irregularly-shaped patch 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 Brown Onyx takes its first flight.

Two views of a mature pupa of the Brown Onyx.


Video: A Brown Onyx emerges from its pupal case.

A newly eclosed Brown Onyx resting near 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.

Text by Horace Tan, Photos by Low Jian Kai, Koh Cher Hern, Khew SK and Horace Tan, Video by Horace Tan.

Butterfly of the Month - April 2024

Butterfly of the Month - April 2024

The Brown Awl (Badamia exclamationis)

It has been a very hot hot April, with temperatures in Singapore soaring in the high 30's. All over Asia, temperatures are at an unprecedented high, and we are not even in the summer months yet! If this is not climate change, then I don't know what is. Historical highs are being recorded year after year and it is quite widely acknowledged by butterfly watchers and enthusiasts that butterfly populations are down in many parts of Asia, compared to a decade ago.

This month, our feature butterfly is the unremarkable Brown Awl (Badamia exclamationis). This is a skipper from the sub-family Coeliadinae and the only representative of its genus in the region. It is a relatively large butterfly and is a fast-flyer like most Hesperiidae species. I've always been intrigued by the latin species name of this Skipper. It's as though the scientist who first described it screamed out loud when he first discovered this butterfly!

The Brown Awl is moderately rare in Singapore, usually observed singly in the early hours of the morning. It has also been observed to puddle occasionally, but where it is encountered, it is more often seen feeding on moisture off damp rocks, stone walls and timber structures in the cooler morning air. There have been few records of the Brown Awl feeding on flowers.

The species is more often encountered in the forested nature reserves than in urban parks and gardens, although it is widely distributed across Singapore and found in various habitats where its caterpillar host plants, Combretum sundaicum and Terminalia calamansanai (both from the Combretaceae family) are found. Where they are observed, they are usually encountered singly.

A Brown Awl perched on a damp rock after feeding off moisture from the rock

A Brown Awl feeding on the flower of the String Bush at Tampines Eco Green

The wings of the Brown Awl are very elongated and the hindwing is caudate at vein 1b, and strongly excavate between veins 1b and 2. Above, the wings are dark brown with greyish green scaling at the wing bases. The female has prominent and elongated hyaline streaks in spaces 1b, 2 and 3, and the cell in the forewing. In contrast, these streaks in the male are rather small and subdued.

A partial upperside view of a male Brown Awl

On the undersides, both sexes are pale greyish brown and largely unmarked. There is a small yellowish sub-tornal spot in space 1b of the hindwing, which usually goes unnoticed as the hindwings typically fold up at the dorsal area. The prominent veins on the underside gives the butterfly a streaked-like appearance. The abdomen of the butterfly is prominently yellow-banded.

Under leaf behaviour of the Brown Awl where it clings on to the underside of a leaf to rest

The Brown Awl occurs from Sri Lanka, India, China through the Malay Peninsula and Singapore to New Guinea, Australia and as far east as Samoa. In Singapore, it is usually encountered feeding at damp rocks or at flowering plants (uncommonly). It has a habit of perching on the undersides of foliage with its wings folded upright and often adopts this position when it is disturbed and flies off to hide under a leaf.

Text by Khew SK : Photos by Khew SK, Koh CH, Dr Lee PC, Billy Oh, Jonathan Soong and Horace Tan

Butterfly of the Month - March 2024

Butterfly of the Month - March 2024

The Indigo Flash (Rapala varuna orseis)

A pristine female Indigo Flash perches on a dew covered grass blade in the early morning hours. Note the slight purplish wash on the wing bases.

March 2024 has whizzed past in a flash, and on this final day of the month, we feature one of our "Flash" butterflies that exists in Singapore. A butterfly that belongs to the Lycaenidae family, called the "Blues and Hairstreaks", these species found in Singapore are mainly classified under the genus Rapala. The Flash butterflies are fast-flying skittish species and are difficult to spot when they flash from perch to perch.

Our feature butterfly for March 2024 is the Indigo Flash (Rapala varuna orseis). It is one of nine extant species from the genus Rapala that have been found in Singapore. Only recently, the early stages of the species were recorded on the local caterpillar host plant, Bridelia tomentosa. The Indigo Flash is often encountered in urban parks and gardens as well as within the nature reserves of Singapore.

The species is skittish and is usually quite alert. It is widely distributed across Singapore, where it is regularly encountered singly but at times more than one individual is spotted in the same location. At certain hours of the day, both sexes are sometimes observed perched on the uppersides of leaves with their wings opened almost flat to sunbathe.

Upside-down behaviour of both sexes of the Indigo Flash where the butterfly perches upside down on leaves and stems

It is sometimes encountered feeding on flowering plants and weeds like Mile-A-Minute, Spanish Needle and Stringbush. When it is resting in the shade, the Indigo Flash sometimes displays an upside-down behaviour where it perches on the undersides of leaves to rest. Both males and females are observed to behave this way.

A female Indigo Flash perched with open wings to sunbathe

A male Indigo Flash showing a glimpse of its deep indigo-blue upperside 

The Indigo Flash belongs to the varuna group of the genus Rapala, where the males and females are a shade of blue or bluish-green on the upperside. Males of the Indigo Flash is indigo blue above and unmarked, whilst females are steely blue and also unmarked. The underside is dark brown in the male and is strongly purple-washed. The female is a lighter brown and usually lacks the purple wash found in the males.

The post discal bands are white-edged, and broader than usual compared to other species in the genus, and darker than the ground colour of the underside. There is a large orange-crowned eyespot at the tornal area of the hindwing, with iridescent blue-green scales adjacent to it. On the hindwing, the cell-end bar is angled towards the post-discal band and closer, often touching each other. There is a white-tipped black filamentous tail at vein 2 of the hindwing.

Note the circular disc on the underside of the hindwing that houses the scent brand in the male Indigo Flash

The eyes of the Indigo Flash are jet-black and smooth. The legs are black-banded. The antennae are also black-banded and orange-tipped at the antennal club. There is a scent brand within space 7 on the hindwing and appears as a prominently raised circular disc on the underside of the males of the Indigo Flash.

Text by Khew SK : Photos by David Chan, Khew SK, Horace Tan, Bene Tay and Mark Wong

Butterfly of the Month - February 2024

Butterfly of the Month - February 2024

The White Royal (Pratapa deva relata)

On this special once-every-four-years day of 29 Feb, we feature one of our "royal" butterflies from the Lycaenidae family. The Lycaenidae, often referred to as the Blues and Hairstreaks, is represented by the largest number of species in Singapore. As many of the species are cryptic and superficially very similar-looking, more species are being added to the Singapore checklist as new information becomes available, or observations of species which were previously missed are included to the list.

Our Butterfly of the Month for February 2024 is the moderately rare White Royal (Pratapa deva relata). This species was a recent re-discovery back in 2007 when it was first photographed at an urban area near Telok Blangah Hills Park. It was subsequently observed that the caterpillars of this species depends on the parasitic mistletoe, Rusty Mistletoe (Scurrula ferruginea) as its host plant. With a more targeted observation of habitats where this parasitic plant grows, it was observed that the species is often present in the vicinity of the host plant.

The White Royal is widely distributed across Singapore and found in urban parks and gardens, as well as the nature reserves and areas where the caterpillar host plant can be found. The distinctive parasitic plant can often be spotted growing on other plants where its "rusty" undersides of its leaves stand out. The adult butterflies are often spotted singly where they occur, but females have been seen in small numbers, ovipositing on its host plants.

Male (top) and Female (bottom) White Royal showing their upperwings

The upperside of the male White Royal is a deep lustrous blue with broad black borders, particularly at the apical area, on the upperside of the forewings and a series of black marginal spots on the hindwings. The females feature paler blue uppersides, also with broad black apical borders on the forewings.

A female White Royal sunbathing with open wings

A "rear view" of the White Royal showing its tornal lobe

The underside of both sexes is greyish white with a series of post-discal narrow black streaks. The underside of the hindwing has a prominent orange-crowned black marginal spot in space 2. There is a pair of white-tipped tails at the ends of veins 1b and 2. The tornal lobe on the hindwing is black and orange with white cilia on pristine individuals.

The eyes of the White Royal are transparent instead of jet black, as in the case with many of the related species. The legs are greyish-white throughout. The antennae are black-and-white banded, and orange tipped at the club.

A female White Royal resting on the leaf of the Rusty Mistletoe after ovipositing

The complete life history of the White Royal has been successfully recorded in Singapore on its single caterpillar host plant, the Rusty Mistletoe (Scurrula ferruginea). This host plant, one of only a few parasitic and hemi-parasitic plants found in Singapore, is featured in an earlier blogpost about Mistletoes and their importance to the butterfly fauna in Singapore. At least 4 species of Lycaenidae caterpillars depends on the Rusty Mistletoe for survival and continued existence in Singapore.

Text by Khew SK : Photos by Khew SK, Loh MY, Richard Ong, Horace Tan, May Yap and Yip Jen Wei