Life History of the Jewel Fourline Blue

Life History of the Jewel Fourline Blue (Nacaduba sanaya elioti)

Butterfly Biodata:
Genus: Nacaduba  Moore, 1881
Species: sanaya   Fruhstorfer, 1916
Subspecies: elioti   Corbet, 1938
Wingspan of Adult Butterfly: 30-34mm
Caterpillar Local Host Plants: Agelaea macrophylla (Connaraceae), Rourea mimosoides (Connaraceae), Agelaea sp. (Connaraceae).

A Jewel Fourline Blue perching on a leaf.

A female Jewel Fourline Blue perching on a stem.

Physical Description of Adult Butterfly:

Above, the male is shining violet blue with a thread-thin border; the female is pale silvery blue with broad border. Underneath, both sexes are greyish brown with two bands in the forewing (post-discal and discal) each composed of a double series of whitish striae. Forewing postdiscal band curved in towards base and dislocated at vein 6. On each hindwing, there is an orange-crowned black tornal spot in space 2 with no presence of bluish-green metallic scales. Next to the tornal spot, a pair of filamentous white-tipped tails occurs at end of vein 2. The female has more rounded forewing termen than the male.

A close-up view of the hindwing of a Jewel Fourline Blue. Note the absence of bluish-green metallic scales in the black tornal spot.

A male Jewel Fourline Blue visiting flowers of Elephantopus scaber (Elephant’s Foot).

A Jewel Fourline Blue puddling on wet ground.

Field Observations of Butterfly Behaviour:

The Jewel Fourline Blue was re-discovered in 2008 and is moderately rare in Singapore. The adults are found in various forested areas of the central catchment reserve, visiting flowering plants, puddling on wet grounds and performing oviposition rituals at young leaves of the host plants.

A mating pair of the Jewel Fourline Blue perching on a stem.

A Jewel Fourline Blue puddling among fallen leaves.

An aberrated Jewel Fourline Blue ovipositing on a young leaf of an unidentified plant.

Early Stages:

The Jewel Fourline Blue is polyphagous. Thus far, three plants in the Connaraceae family have been identified as the larval hosts in Singapore. They are Agelaea macrophylla, Rourea mimosoides and another Agelaea plant with the species id yet to be finalized. All three plants are common in the catchment reserves. Caterpillars of the Jewel Fourline Blue mainly feed on young leaves of the host plant. As in the case for most lycaenid species, the caterpillars of the Jewel Fourline Blue are tended by ants.

Local host plant #1: Agelaea macrophylla.

Local host plant #2: Rourea mimosoides.

Local host plant #3: Agelaea sp..

Eggs are laid singly on a young leaf or stem of the host plant. Each egg is whitish with a green undertone. It has a thick discoid shape, and features a depressed micropylar on top. The egg surface is finely reticulated, slightly raised at the intersections of cris-crossing ridges. The egg has a diameter of about 0.5mm.

A mother Jewel Fourline Blue ovipositing on a young leaf of Agelaea sp. .

A mother Jewel Fourline Blue ovipositing on a young leaf of Agelaea macrophylla.

Two newly laid eggs of the Jewel Fourline Blue on a stem of an Agelaea sp.

Two views of an egg of the Jewel Fourline Blue laid on leaf surface of an Agelaea sp.

It takes about 2 days for the egg to hatch. The young caterpillar consumes part of the egg shell to emerge. With a length of about 1mm, it has a pale yellowish body with long setae (hairs) dorsally and sub-spiracularly. The body color changes gradually to a darker shade of yellow as growth progresses. The first instar lasts for 2-2.5 days and the body length reaches about 2mm before the moult to the 2nd instar.

A newly hatched caterpillar of the Jewel Fourline Blue, resting next to its empty egg shell.

Two views of a newly hatched caterpillar of the Jewel Fourline Blue, length: 0.9mm.

Two views of a 1st instar caterpillar of the Jewel Fourline Blue, length: 2mm.

Two views of a late 1st instar caterpillar of the Jewel Fourline Blue, dormant prior to its moult.

In the second instar, dorsal setae are much shortened proportionately compared to those in the first instar. Moreover, there are numerous short setae present all over the body surface. The body color is variable, whitish to yellowish or pale reddish brown. The 2nd instar lasts about 3 days and the caterpillar grows to a length of about 3.5mm before the moult to the 3rd instar.

Two views of a 2nd instar caterpillar of the Jewel Fourline Blue, length: 2.6mm.

Two views of a 2nd instar caterpillar of the Jewel Fourline Blue, length: 2.8mm.

Two late 2nd instar caterpillars of the Jewel Fourline Blue, dormant prior to their moult to the 3rd instar.

The 3rd instar caterpillar has similar body coloration as in the 2nd instar. The dorsal nectary organ and tentacular organs are now easily discernible. After about 3 days in this instar with the body length reaching about 6-5.5mm, the next moult brings the caterpillar to its final instar.

Two views of an early 3rd instar caterpillar of the Jewel Fourline Blue, length: 3.8mm.

Two views of a 3rd instar caterpillar of the Jewel Fourline Blue, length: 6.2mm.

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

A well-concealed caterpillar of the Jewel Fourline Blue observed with attending ants on young leaves of Rourea mimosoides.

The 4th instar caterpillar has the same pale yellowish to reddish brown ground color as in the 3rd instar. As in the 3rd instar, the dorsal nectary organ and tentacular organs are prominent on the posterior segments. Tentacular organs are readily everted when the caterpillar are disturbed or when attending ants are present.

An early 4th instar caterpillar of the Jewel Fourline Blue.

Two views of a 4th instar caterpillar of the Jewel Fourline Blue, length: 12.5mm.

Two views of a 4th instar caterpillar of the Jewel Fourline Blue, length: 14mm.

A 4th instar caterpillar of the Jewel Fourline Blue found in the field, feeding on a young leaf of an Agelaea sp., with ants in attendance.

The 4th instar lasts for 4-5 days and the body grows up to a length of about 14mm. On the last day of this instar, the caterpillar ceases food intake and its body shrinks in length and its body colour changes to orangy to pinky brown. The fully grown caterpillar finally chooses a spot on a leaf surface where it readies the site for pupation by spinning a silk pad and a silk girdle to secure itself.

A 4th instar caterpillar of the Jewel Fourline Blue, late in this stage, with color change taken place.

Two views of a girdled-down pre-pupa of the Jewel Fourline Blue.

About 1 day later, pupation takes place. The pupa has the typical lycaenid form, and is 8-8.5mm in length. It is mostly pale yellowish brown and speckled with black spots of various sizes and shapes.

Two views of a freshly pupated pupa of the Jewel Fourline Blue, with colour yet to change to yellowish brown.

Two views of a pupa of the Jewel Fourline Blue.

Five days later, the pupa becomes darkened in color signaling the imminent emergence of the adult. The markings on the forewing upperside becomes increasing obvious through the pupal skin. The next day the adult butterfly emerges from the mature pupa. Pupal period: 6 days.

Two views of a mature male pupa of the Jewel Fourline Blue, showing extensive purplish blue coloration in the wing pad.

Two views of a mature female pupa of the Jewel Fourline Blue, showing much less extensive bluish coloration in the wing pad.

A newly eclosed male Jewel Fourline Blue 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.
• A Field Guide to the Butterflies of Singapore, Khew S.K., Ink On Paper Communications, 2nd Edition, 2015.
• Butterflies of Thailand, Pisuth Ek-Amnuay, 2nd Edition, 2012.

Text by Horace Tan, Photos by Koh Cher Hern, Low Jian-Kai, Lumin Ong, Sebastian Ow and Horace Tan.

Butterfly of the Month - August 2026

Butterfly of the Month - August 2026

The Starry Bob (Iambrix stellifer)

A Starry Bob feeding on the flower of the Bandicoot Berry (Leea indica)

We have just passed the peak of the summer season in the northern hemisphere this month. The summer of 2026 has become one of the most talked-about seasons in recent years, with record-breaking temperatures, prolonged heatwaves, and growing concerns about climate resilience across the globe sparked by an extreme El Nino effect. At least 35,000 people died during Europe’s four record-breaking, back-to-back heatwaves this summer than would normally be expected, as many countries like France, Germany and Spain recorded temperatures in excess of 40degC.

News of the war in the Middle East seems to have tapered off as the US and Iran's on-and-off ceasefire has made the region experience a new norm as far as peace is concerned. The US' imposition of new tariffs has initiated a different kind of "war" amongst various nations, and in the recent week, US-Canada relations appear to have taken a turn for the worse. And to add some "humour" into the fray, the US President has unilaterally decided to re-name Lake Ontario to Lake America to spite Canada!

Singapore celebrated its 61st birthday after independence, and this year's National Day Parade returns to the National Stadium after the last parade was held at the Stadium in 2016. Traditionally the NDP is held at the Padang and Marina Bay Floating Platform. The venue at the Stadium can accommodate up to 55,000 spectators compared to the smaller venues at the Padang and Marina Bay. In future, with the completion of the NS Square in 2027, which will replace the Floating Platform at Marina Bay, the NDPs will likely return to the Marina Bay area.

A Starry Bob feeding on the flower of the Elephant's Foot (Elephantopus scaber)

Local news that dominated online portals for a while involved an altercation between a concerned father who physically attacked a senior person who patted his daughter on the head, supposedly because he found the little girl cute. It sparked off a debate amongst netizens about personal physical boundaries, society's interpretation of any physical interactions with children and the use of uncalled for physical force on a senior citizen. Eventually, the victim was found to have a fracture after his fall and further investigations by the authorities are ongoing.

Also dominating the news in Singapore were nature groups and other stakeholders' call for the conservation of forested land at Maju Forest and Gillman Barracks areas that the government had announced plans for public housing. As the debates continue and feedback collected to decide on the eventual extent of forest clearance, another announcement regarding the amalgamation (and reclamation) of the islands off the south-west coast of Singapore sparked concern about the potential loss of biodiversity in the marine and intertidal habitats.

Our Butterfly of the Month for August 2026 is a small Hesperiidae, or Skipper, the Starry Bob (Iambrix stellifer). One of two species of the genus Iambrix that can be found in Singapore, the Starry Bob is much rarer that its common cousin, the Chestnut Bob (Iambrix salsala). The Starry Bob is a forest-dependent species and seldom found outside the sanctuary of Singapore's forested areas.

The adults are small and the 3rd segment of the palpi is long and thin, appearing like a "horn" when viewed close up. On the upperside, both sexes are dark brown. The male is unmarked but the female has several white post-discal spots on the forewing. The eyes are dark brown throughout, whilst the antenna is brown with a tinge of orange just behind the apiculus.

On the underside, the wings are brown to dark brown overlaid with ochreous scales. In pristine individuals, the apical area of the forewing is shaded a distinct orange to yellowish brown. There are variable number of silvery spots on both wings. In fully-spotted specimens, the forewing features post-discal spots in spaces 2-5 and one spot near cell-end, and the hindwing features post-discal spots in spaces 1b, 2, 5 and 7, and one spot near cell-end. Noteworthy is that the spot in space 5 on the hindwing lies further out and about half way between cell-end and the wing margin. In the look-alike species Chestnut Bob (Iambrix salsala), this spot lies just beyond the cell.

A Starry Bob puddling on damp ground

The caterpillar host plants of the Starry Bob are grasses that are mainly found in forested areas - Centotheca lappacea (Poaceae, common name: Sefa), Lophatherum gracile (Poaceae).

Text by Khew SK : Photos by Khew SK, Koh CH, Loh MY, Low JK, Jonathan Soong, Horace Tan, Anthony Wong and Benjamin Yam.