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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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