26 September 2009

Life History of the Rustic

Life History of the Rustic (Cupha erymanthis lotis)



Butterfly Biodata:
Genus: Cupha Billberg, 1820
Species: erymanthis Drury, 1773
Subspecies: lotis Sulzer, 1776
Wingspan of Adult Butterfly: 55mm
Caterpillar Local Host Plants: Flacourtia rukam (Flacourtiaceae)
, F. inermis (Flacourtiaceae)


A Rustic puddling on wet ground in the nature reserves.


A Rustic perching on a leaf.

Physical Description of Adult Butterfly:
Above, the forewing is orange brown in the basal area and black at the apical area with several subapical spots lying within; in between there is a broad pale yellowish discal patch containing three or four dark brown spots in spaces 2, 3 and 4. The hindwing is mainly orange brown and have narrow marginal, submarginal and postdiscal bands with a discal series of black spots in spaces 2 to 6. Underneath, the wings are much paler and the apical area in the forewing is pale brownish. On the forewing, there is a narrow discal line bordered outwardly by a series of black spots, and on the hindiwng there is a postdiscal pale lunular band and a discal series of pale lunules bordered outwardly by black spots.


Another puddling Rustic in the nature reserve.

Field Observations of Butterfly Behaviour:
This species is rather common in the Central Catchment Nature Reserve. The fast flying adults can be frequently seen flying around shrubs and bushes found alongside various trekking trails in the nature reserve. However, on the wing, one can easily confuse it with Banded Yeoman (Cirrochroa orissa orissa). The restless adults make it rather difficult to photograph them in the field. Rare opportunities to do so only arise when they stop briefly to visit flowers or to puddle on wet grounds.

Early Stages:
The local host plant found in the Central Catchment Reserve, Flacourtia rukam, is a small evergreen tree with thorny stems and branches. Its leaves are elliptic and crenulate, and reddish brown to red when they are young. Its flowers are small and unisexual and occur in axillary clusters. The pink to reddish berry is globose and is good for making jam. The caterpillars of the Rustic feed mainly on young leaves of the host plant.


Local host plant: Flacourtia rukam in the nature reserves.


A mating pair of the Rustic.

The eggs of the Rustic are laid singly on the undersides of young leaves, typically on a young sapling of the host plant. The white or pale yellow eggs are somewhat globular in shape and more produced near the top where the micropylar is. The surface is marked with small pits which are roughly hexagonal higher up and rectangular lower down. Each egg has a diameter of about 0.9mm, and a height of about 1mm.


A female Rustic ovipositing on a young sapling of Flacourtia rukam.



Left: Fresh egg of the Rustic. Right: Mature egg of the Rustic.
Diameter: 0.9mm; height: 1mm.

The egg takes about 2.5 days to hatch. The young caterpillar emerges by eating away part of the egg shell. The rest of the egg shell becomes the first meal for the newly hatched, which has a cylindrical and creamy white body covered with many small tubercles and short setae. In the abdominal segments, reddish and yellowish internal structure can bee seen through the translucent skin. The head capsule is yellowish brown with the front portion black.


Two views of a newly hatched caterpillar of the Rustic, length: 2mm.

The 1st instar caterpillar feeds on the lamina of young leaves and between feeds, it typically rests on leaf underside against the midrib. As it grows rapidly in this instar, the base body changes to yellow, and thoracic segments and posterior abdominal segments turning reddish. After reaching about 4mm in 1.5-2 days, the caterpillar moults to the 2nd instar. Noteworthy is the prominent enlargement of a number of tubercles at the base of the setae towards the end of the 1st instar. These tubercles will give rise to the branched processes in the 2nd instar.


Two views of a 1st instar caterpillar, length: 3mm.


Two views of a late 1st instar caterpillar, prior to its moult, length: 4mm.

The body of the 2nd instar caterpillar is yellowish brown in base color with a green undertone. As in the late 1st instar, the thoracic segments and last few abdominal segments are mainly reddish brown. Long and branched white processes run along the length of the body. On each side of the body, there are three series of such processes: One occurs dorso-laterally, one super-spiracularly and the last, the shortest, runs sub-spiracularly. The head capsule is yellow with two large black patches on the front portion. This short instar lasts about 1.5 days with the body length reaching about 6mm.


Two views of a 2nd instar caterpillar, length: 6mm


Three snapshots of the moult from the 2nd instar to the 3rd instar.
Top: late 2nd instar; Middle: with old skin just shredded; Bottom: with the new processes inflated.



Moulting to the 3rd instar and the inflation of the new processes at 4x speed.


The 3rd instar caterpillar has the dorso-lateral and super-spiracular processes black in color. A white band links up the base of the sub-spiracular processes. Above this white band, the body color is dark red with a green undertone. This instar takes about 1.5 days to complete with body length reaching about 10-11mm.


Two views of a 3rd instar caterpillar, late in this stage, length: 11mm.

Compared to the 3rd instar, the 4th instar caterpillar has proportionately longer processes. Otherwise, there is essentially no change in external appearance. The 4th instar lasts 3 days with the body length reaching about 18mm-20mm.


Two views of a 4th instar caterpillar, length: 16.5mm.


Two views of a 4th instar caterpillar, late in this stage, length: 20mm.

The 5th and final instar is similar to the 4th instar caterpillar except for the appearance of numerous small white spots on the body surface and that the sub-spiracular processes are black in their distal halves.


Two views of a 5th instar caterpillar, length: 27mm.


Frontal view of the head capsule of a 5th instar caterpillar.

The 5th instar lasts for 3 to 3.5 days, and the body length reaches up to 26-28mm. On the last 0.5 day, the color of the entire body changes to yellow and then eventually to lawn green or yellow green. The caterpillar ceases feeding and wanders around. Eventually it stops at a spot on the underside of a leaf, and spins a silk pad from which it hangs vertically to take on the pre-pupatory pose.


The 5th instar caterpillar with its body color changed at the end of this instar.


Two views of an immobile pre-pupatory larva.

Pupation takes place about 0.5 days later. The pupa suspends itself from the silk pad with no supporting silk girdle. It is entirely green. Dorso-laterally there are five long pairs of red and black-tipped processes, and five pairs of small tubercles. Each long process has a broad silver-colored base. There is also a slender silver patch along the leading edge of the wing pad. Length of pupae: 18-19mm.


Two views of a shining pupa of the Rustic.


Two views of a mature pupa of the Rustic. Note the prominent discal patch in the black wing pad.

After about 4 days of development, the pupal skin of the mature pupa turns translucent and the broad discal patch on the forewing upperside become discernible as a result. The eclosion event takes place the next day.


A newly eclosed Rustic drying its wings at its pupal case.


A newly eclosed Rustic resting on the young leaves of its host plant.

References:
  • The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, The Malayan Nature Society.
  • Butterflies of Thailand, Pisuth Ek-Amnuay, 1st Edition, 2006
Text by Horace Tan, Photos by Federick Ho, Khew S K and Horace Tan