Butterfly Biodata:
Genus: Nacaduba Moore, 1881
Species: kurava Moore, 1858
Subspecies: nemana Fruhstorfer, 1916
Wingspan of Adult Butterfly: 26-30mm
Caterpillar Local Host Plant: Ardisia elliptica (Myrsinaceae, common name: Seashore Ardisia).
Physical Description of Adult Butterfly:
Above, the male is violet blue with a thread-thin border (with underside markings visible due to transparency); the female is pale shining blue becoming whitish beyond the forewing cell. Underneath, both sexes are greyish brown with three bands (post-discal, discal and basal) each composed of a double series of whitish striae inwardly lined with dark striae. Forewing postdiscal band is usually straight. On each hindwing, there is an orange-crowned tornal spot in space 2 lightly speckled with bluish-green metallic scales. Next to the tornal spot, a pair of filamentous white-tipped tails occurs at end of vein 2. Forewing submarginal spots are mostly rounded or with scalloped inner margins. In the hindwing, the postdiscal band is usually close to the submarginal band, and submarginal spot 6 is large and often quadrate. The female has more rounded forewing termen than the male.
Field Observations of Butterfly Behaviour:
The Transparent Sixline Blue is moderately common in Singapore. The adults have been seen flying in the vicinity of the host plant, visiting flowering plants, puddling on wet grounds and performing oviposition rituals at developing inflorescence of the host plant.
Early Stages:
The Transparent Sixline Blue is polyphagous. However, for Singapore, only one local host plant, Ardisia elliptica, has thus far been recorded. Caterpillars of the Transparent Sixline Blue mainly feed on leaves and flower buds of the host plant. As in the case for most lycaenid species, the caterpillars of the Transparent Sixline Blue are tended by ants.
Eggs are laid singly on a 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. Th egg has a diameter of about 0.6mm.
It takes about 2.5-3 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 head is black in colour in this instar. The body color changes gradually to a brighter 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.
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 mainly pale yellow while the head is pale reddish brown. The 2nd instar lasts for 2-2.5 days and the caterpillar grows to a length of about 4mm.
The 3rd instar caterpillar is pale yellowish with a green undertone. The dorsal nectary organ and tentacular organs are now easily discernible. After about 3 days in this instar with the body length reaching about 7-7.5mm, the next moult brings the caterpillar to its final instar.
The 4th instar caterpillar has the same pale yellowish ground color as in the 3rd instar, but some individuals also possess a reddish/pinkish dorsal band and/or small reddish dorso-lateral marks. 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 senses a threat (such as from a competing caterpillar) or when attending ants are present.
The 4th instar lasts for 4-5 days and the body grows up to a length of about 14-14.5mm. On the last day of this instar, the caterpillar ceases food intake and its body shrinks in length and decolorises to a dull shade of yellowish to pinky brown. The fully grown caterpillar finally comes to rest on a spot among leaves where it readies the site for pupation by spinning a silk pad and a silk girdle to secure itself.
About 1 day later, pupation takes place. The pupa has the typical lycaenid form, and is 9-10.2mm in length. It is mostly pale yellowish brown and speckled with black spots of various sizes and shapes.
Four to 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: 5 to 6 days.
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.
