Life History of the Chequered Lancer (Plastingia naga)
Butterfly Biodata:
Genus: Plastingia Butler, 1870
Species: naga de Nicèville, 1884
Wingspan of Adult Butterfly: 38-45mm
Caterpillar Local Host Plant: Caryota mitis (Arecaceae; common name: Fishtail Palm).
Physical Description of Adult Butterfly:
Above, the wings are brown with the forewing adorned with pale yellow hyaline spots in the cell-end and spaces 2, 3, 6 and 7, and a narrow yellow streak in space 1b. A series of interneural yellowish streaks is present in the hindwing. Beneath, the wings bear a striking pattern of black veins and whitish rectangular spots on a black background. The abdomen is black and white banded.
Field Observations of Butterfly Behaviour:
The Chequered Lancer is moderately common in Singapore. Sightings are rather frequent in nature reserves and in parks where its host plant, the FishTail Palm, is commonly found. The adults are fast flyers and are skittish when disturbed. They have been observed to visit flowers and sunbath in sunny weather, and to puddle on bird dropping.
Early Stages:
Thus far only one local host plant, the FishTail Palm, has been established for Chequered Lancer. This plant is widely distributed in Singapore and is very common in both nature reserves and various urban parks. The caterpillars of the Chequered Lancer feed on the leaves of the host plant in all instars, and live in leaf shelters. The first two to three instars construct tent-like shelters whereas the final two instars have shelters constructed in a curry-puff shape. As the caterpillar grows in size later through progressing instars, it will move to ever larger shelters built by joining cut leaf fragments on the same leaflet.
Host plant: Fishtail Palm.
The eggs are laid singly or in a small group up to 4 eggs on the upper surface of a leaf of the host plant. Each shallow dome-shaped egg is wine red with yellowish to whitish longitudinal ridges emananting from a similarly coloured ring encircling the micropylar. The eggs are rather large with a diameter of about 1.4-1.5mm.
It takes about 5 days for the egg to hatch. The egg decolorises to a dull shade of milky yellow when fully mature on the last day of this phase. The young caterpillar eats just enough of the shell to emerge, but it makes only a feeble attempt to eat the remaining egg shell. The newly hatched has a length of about 2.8mm. Its pale yellowish brown body is cylindrical in shape and there is a tuff of moderately long setae on the posterior segment. Its head is black.
After abandoning the empty egg shell, the newly hatched caterpillar constructs its first leaf shelter typically on the edge of the same leaflet of the palm frond. Its body takes on a slight green undertone after a few feeding sessions on the leaf. The 1st instar takes a total of 3 days to complete with body length reaching about 5mm.
The unmarked body of the 2nd instar caterpillar resembles that of the first instar. The head capsule is dark reddish brown to black. The tuff of moderately long setae is now absent, being replaced by a few short setae. This instar lasts a total of 3-4 days with the body length reaching up to 7mm.
The 3nd instar caterpillar resembles the 2nd instar caterpillar in being unremarkable. This instar lasts a total of 3-5 days with the body length reaching up to 11mm.
Besides being proportionately larger, the 4th instar caterpillar retains the same body features from its earlier instars. In some specimens, instead of being totally black, the head capsule could appear in brown with pale yellowish brown stripes on both sides of the coronal sulcus. This penultimate instar lasts 4-5 days with the body length reaching up to 17-18mm.
The body of the 5th instar caterpillar is pale yellowish to whitish. The most prominent change from the 4th instar to the 5th takes place on the head capsule which has become pale biege brown with a thin white stripe on both sides of the coronal sulcus continuing to the white patch near to the mandible. The periphery of the head capsule is marked in dark brown.
The 5th instar takes about 4-5 days to complete with the body length reaching up to 31-33mm. In the last 1-2 days of this instar, the caterpillar seeks out a new site on a leaflet to construct its leaf shelter. At this stage, its underside starts to excrete some whitish powdery substance. Within the pupation shelter, a large amount of silk threads are spun and a great mass of small whitish particles are accumulated. Typically the pupation shelter is cut from the leaflet before the caterpillar proceeds to seal the shelter. This prepupatory phase lasts for 1.5-2 days.
Pupation takes place within the leaf shelter. The pupa does not have a cremastral attachment nor a silk girdle and it is mainly secured with tightly woven silk threads in the shelter. It has a short thorax and a rather long abdomen. The body is darker brown in the thorax and wing pad areas, but paler brown in the abdomen. Length of pupae: 18-19.5mm.
After 8-9 days, the pupa becomes mostly black as the adult development stage within its case comes to an end. Eclosion takes place the next day.
References:
- [C&P4] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society.
- Butterflies of Thailand, Pisuth Ek-Amnuay, 2nd Edition, 2012
- A Field Guide to the Butterflies of Singapore, Khew S.K., Ink On Paper Communications, 2010.
