Butterfly Biodata:
Genus: Ancema Eliot, 1973
Species: blanka de Níceville, 1894
Subspecies: blanka de Níceville, 1894
Wingspan of Adult Butterfly: 28-33mm
Caterpillar Local Host Plant: Viscum ovalifolium (Santalaceae, common name: Oval-leaved Mistletoe).
Physical Description of Adult Butterfly:
The eyes are greenish. On the wing upperside, the male is bright shining blue with black border and radiating blue streaks towards the termen. The female is of a paler blue with broad black border on both fore- and hindwing which are rounder than those of the male. On the wing underside, the male is greyish white with a slivery sheen whereas the female is pale greyish brown. There is a post-discal series of narrow dark streaks, very much more obscure on the forewing than on the hindwing. In the hindwing, there are black tornal spots in spaces 1a and 2, crowned with orange patches. Each hindwing has a pair of white-tipped black tails at ends of veins 1b and 2.
Field Observations:
The Silver Royal is very rare in Singapore. It was re-discovered in 2005 where a single individual was spotted feeding at the flowers of a Syzygium tree. Since then there have been a few sporadic sightings at various locations in the Southern Ridges. The fast flying adults have often been sighted while visiting flowers at tree top or hill top. The male has also been observed to puddle at damp footpaths.
Early Stages:
In Singapore, so far only one larval host plant for Silver Royal has been identified. This plant is the Oval-leaved Mistletoe (Viscum ovalifolium ), the same parasitic plant utilized by the early stages of the Golden Royal (Pseudotajuria donatana donatana). On this plant, the early stages of the Silver Royal in all instars feed mainly on the leaves, and occasionally the flower buds of the host plant.
Eggs are laid singly on various parts of the host plant, such as the leaf, flower buds and fruits. Each whitish egg is about 0.8mm in diameter. It is dome-shaped with a depressed micropylar at the pole and its entire surface is covered with pits. When freshly laid, the egg has a strong greenish tone in the micropylar and surface pits.
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 1.2mm. Long setae (hairs)
run along the length of the body dorsally as well as sub-spiracularly. The head is brown in colour. The newly hatched does not bother to eat the remnant of the egg shell and proceeds to feed on leaf surface in the vicinity.
The 1st instar lasts about
2 days with the body length increased to about 2.5mm. Before the moult, the caterpillar typically take up its position on the surface of a leaf, and becomes immobile.
The 2nd instar caterpillar has numerous short setae covering its body surafce. The caterpillar now features a dark-brown diamond-shaped prothoracic shield. The dorsal nectary organ on the dorsum of the 7th abdominal segment is discernible and whitish. As it grows in this instar, the yellowish brown body gradually turns greenish. The 2nd instar lasts about 2 days, with the body length reaching up to about 4.1mm.
The 3rd instar caterpillar resembles the 2nd instar caterpillar initially, but with a prominent and proportionately larger prothoracic shield and greater density of body setae. The prothoracic shield is dark brown with a central white streak and two small lateral white patches. As it grows in this instar, the body turns increasingly dark greenish overall. The dorsal nectary organ at this late stage has the white coloration confined to its central part. The 3rd instar lasts about 2 days and the body length increases up to 7.5mm.
The 4th instar caterpillar resembles the late 3rd instar caterpillar in most body features/markings. One distinguishing feature is that the prothoracic shield is now mostly whitish. The 4th instar lasts about 3 days with the body length reaching up to 13mm.
The 5th instar caterpillar resembles the 4th instar caterpillar closely in most body features/markings which are proportionately larger than those in the 4th instar. The 5th (and final) instar lasts about 3 days with the body length reaching up to 22mm.
As it enters the pre-pupatory phase of its life cycle, the caterpillar ceases its feeding activity and wanders around for a pupation site. As is the case for the Golden Royal, the pre-pupatory caterpillar of the Silver Royal settles for a spot on the upperside of a leaf with a strong preference for a leaf with curled up edges offering some degrees of concealment. At the chosen site, it spins a silk pad and a silk girdle to secure itself to the leaf.
After about 1 day of the pre-pupal period, pupation takes place. The pupa
is held via its cremaster to the silk pad on the leaf surface. It is 12 to 13mm in length, with the typical shape for a lycaenid pupa, albeit more rotund and broader than usual. The pupa is yellowish green with numerous whitish transverse streaks. In addition, reddish brown spots appear on the dorsum of the abdomen. There is near-diamond-shaped reddish brown patch on the dorsum of the metathorax with two small black spots anterior to the patch.
The pupal period is observed to be 7.5 days for the female and 8.5 days for the male. On the night before ecloson, the pupa becomes darkened in color signaling the
imminent emergence of the adult. One can now tell the sex of the soon-to-emerge butterfly from the coloration of the wing pad at this stage. The next morning the adult butterfly emerges from the mature pupa.
A male Silver Royal emerging from 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).
- 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.
