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

Life History of the Influent Royal

Life History of the Influent Royal (Tajuria dominus dominus)

Butterfly Biodata:
Genus: Tajuria Moore, 1881
Species: dominus Druce, 1895
Subspecies: dominus Hewitson, 1878
Wingspan of Adult Butterfly: 26-30mm
Caterpillar Local Host Plant: Dendropthoe pentandra (Loranthaceae, common name: Malayan Mistleoe).

Physical Description of Adult Butterfly:
The eyes are greenish. On the upperside, the male is bright blue with black distal borders on both forewing and hindwing; the female is pale blue with black borders. On the forewing, the male has a large circular black patch near end-cell while the black border in the female is narrower, reaching near cell apex. On the underside, both sexes are drab greyish brown with a postdiscal series of white-edged dark striae on both wings, and a series of indistinct dark marginal and sub-marginal fasciae. The post-discal band is closer to the cell than to the termen. In the hindwing, black tornal spots are present in spaces 1a and 2, and a large blush green patch is present in space 1b between the tornal spots. Adjacent to these featues in spaces 1a to 2, a prominent and broad orange patch extends inwards to touching the postdiscal straie, as well as upwards into space 3 and downwards into space 1. Each hindwing has a pair of white-tipped black tails at ends of veins 1b and 2.

Field Observations:
The Influent Royal is rare in Singapore. It was re-discovered in 2006 at an urban garden. Since then, sporadic sightings of this species have mostly taken place at the fringe of nature reserve as well as several urban residential areas. The fast-flying adults have a preference for resting at treetop level and rarely descend except to feed on flowering plants.

Early Stages:
In Singapore, thus far only one larval host plant has been confirmed. This local larval host is the Malayan Mistletoe (Dendropthoe pentandra),the most common mistletoe in Singapore. On this plant, the early stages of the Influent Royal feed on the young leaves and young stem, with a strong preference for the latter in later instars.

Local host plant: Dendropthoe pentandra (Malayan Mistletoe).

Eggs are laid singly on the young shoots of the host plant. Each egg is about 0.7mm in diameter, white with a strong greenish tinge when freshly laid. It is bun-shaped with a depressed micropylar at the pole and a surface reticulated with polygonal depressions. Short spikes raised from the ridges encircling these depressions.

An Influent Royal laying an egg on a young leaf of the Malayan Mistletoe.

Two vlews of an egg of the Influent Royal.

Two views of a fully developed egg with the caterpillar ready to emerge.

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 yellowish brown in coloration, and has a length of about 1.1mm. Long setae (hairs) run along the length of the body dorsally as well as sub-spiracularly. Raised dorsal tubercles are transparent. The body also features a diamond-shaped pale brown prothoracic shield and a pale brown anal plate. As it grows in this instar, the body ground colour turns whitish gradually. The 1st instar lasts about 3 days with the body length increased to about 2.3mm.

A newly hatched caterpillar next to its empty egg shell.

Two views of a newly hatched caterpillar, length: 1.1mm.

Two views of a 1st instar caterpillar, length: 1.5mm.

A late 1st instar caterpillar of the Influent Royal, dormant prior to the moult to the next instar.

In the 2nd instar caterpillar, the dorsal tubercles are proportionately reduced in size, and the long dorsal setae seen in the 1st instar are now absent. Initially, the body is adorned with streaks of pale and diffused yellowish markings against a whitish ground colour. Pale brown prothoracic shield and anal plate are present. The dorsal nectary organ is also featured on the dorsum of the 7th abdominal segment. As it grows in this instar, the yellowish markings gradually lose prominence and the body takes on a greenish undertone. The 2nd instar lasts for about 3 days, with the body length reaching up to 4.7mm.

A newly moulted 2nd instar caterpillar, eating its old skin.

Two views of a 2nd instar caterpillar of the Influent Royal, early in this instar, length: 2.5mm.

Two views of 2nd instar caterpillar of the Influent Royal, late in this instar, length:4.6mm.

Two views of a 2nd instar caterpillar, dormant prior to its moult.

Initially, the 3rd instar caterpillar resemble the 2nd instar closely. On close inspection, the body surface is adorned with numerous small pale brownish setae. As growth progresses in this instar, the dorsal tubercles on the mesothorax and the 5th abdominal segment becomes darkened in color. The dorsal nectary organ on the 7th abdominal segment and the tentacular organs on the 8th abdominla segment are now easily discernible. After about 2-3 days in the 3rd instar, the moult to the 4th instar takes place.

Two views of an early 3rd instar caterpillar, length: 6.2mm.

Two views of a 3rd instar caterpillar feeding on a young leaf of the Malayan Mistletoe, length: 8.1mm.

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

The 4th caterpillar is generally greenish and featuring prominent whitish bands and patches. A super-spiracular whitish band runs from the prothorax to 4th abdominal segment just above spiracles. Another one runs low along the body rim from the anterior segment to the 8th abdominal segment. Two obligue lateral whitish patches occur in abdominal segments 2-4, and 6-8. On the dorsum, there is a prominent triangular whitish patch on abdoment segments 4-6. The anal plate is also flanked with whitish patch on three sides. The tips of tdorsal tubercles on the mesothorax, metothorax and the 5th abdominal segments are reddish brown. In some caterpillars, there are additional black markings on the side of the prothoracic shield, and on the lower part of abdominal segments 1, 4 and 6. The 4th (and final) instar lasts about 3-3.5 days with the body length reaching up to 16mm.

Two views of a newly moulted 4th instar caterpillar, eating its old skin.

Frontal view of a 4th instar caterpillar, showing the diamond-shaped prothoracic shield.

The frontal view of another 4th instar caterpillar, showing black markings on the side of the prothoracic shield.

A 4th instar caterpillar of the Influent Royal feeding on a young stem of the Malayan Mistletoe. This caterpillar has black markings in the prothorax, and abdominal segments 1, 4 and 6.


Video: A 4th instar caterpillar of the Influent Royal feeding on a young stem of the Malayan Mistletoe.

Two views of a 4th instar caterpillar, length: 12mm. This caterpillar does not have black markings in the prothorax, and abdominal segments 1, 4 and 6.

Two views of a 4th instar caterpillar feeding the leaf of the Malayan Mistletoe, length: 16mm.

As the 4th instar comes to an end, the greenish part of the body gradually turn black. Soon after, the caterpillar ceases its feeding activity and its body gradually shrinks in length. The pre-pupatory caterpillar wanders around for a suitable pupation site. Typically it settles for a spot on the stem of the host plant, and on the surface of a leaf. At the chosen pupation site, it stays dormant for about 0.5 day or so before spinning a silk pad to which it attaches itself via claspers at the posterior end.

Two views of a late 4th instar caterpillar, length: 16mm.

Two views of an early pre-pupa of the Influent Royal.

Two views of a pre-pupa of the Influent Royal.

About 0.5 day after the pre-pupatory caterpillar secures itself to the pupation site, pupation takes place. The pupa is held firmly via its cremaster to the silk pad. It is 10.8 to 11mm in length, with the typical shape for a lycaenid pupa. It is mostly whitish in the thorax, the wing pads and the lower part of the abdomen, brownish in the front portion of the prothorax, and the dorsum of the abdomen. Thin whitish dorso-lateral line segments, a triangular pale brown markings are embedded in the brown dorsal patch. Two short cephalic horns are also present.

Two views of a pupa of the Influent Royal, length: 10.8mm.

Three views of a developing male pupa. Left: day 1; middle: day 7; right: day 8.

Seven days later, the pupa becomes darkened in color signaling the imminent emergence of the adult. The next day the adult butterfly emerges from the mature pupa (pupal period: 8 days).

Video: A male Influent Royal emerges from its pupal case.

A newly eclosed male Influent Royal resting next to its pupal case.

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, 2nd Edition, 2015.

Text by Horace Tan. Photos by Loh Mei Yee, Jonathan Soong and Horace Tan. Videos by Loh Mei Yee and Horace Tan.