THE BUTTERFLY: Life History of the Tawny Palmfly

Life History of the Tawny Palmfly (Elymnias panthera panthera)

Butterfly Biodata:
Genus: Elymnias Hübner, 1818
Species: panthera Fabricius, 1787
Subspecies:panthera Fabricius, 1787
Wingspan of Adult Butterfly: 50-60mm
Caterpillar Local Host Plants: Caryota mitis (Arecaceae, common name: Fish Tail Palm), Licuala spinosa (Arecaceae, common name: Mangrove Fan Palm), Ptychosperma macarthurii (Arecaceae, common name: MacArthur Palm).

Physical Description of Adult Butterfly:
Termens of both wings are prominently scalloped. The hindwing is strongly toothed at vein 4. Above, the wings are dark brown. On the hindwing, there is a submarginal pale buff band bearing fuscous interneural (between the veins) spots. Underneath, the wings are strongly mottled brown, with the submarginal to post-discal areas pale buff. On the hindwing there is a series of black-crowned white interneural spots in spaces 1b,2,3,4,5 and 6, with the white spot in space 6 much larger and ringed in black.

Field Observations of Butterfly Behaviour:
The Tawny Palmfly is moderately common in Singapore and can be found in the nature reserves, forested areas of wastelands in the west, Sungei Buloh wetland reserve and Kranji nature trail. The adults are typically shade-loving, and are usually sighted flying along the edge of forested area and in the vicinity of a clump of palm trees. The adults have the habit of visiting flowers and ripened fruits of the Singapore Rhododendron for mineral and energy intakes.

Early Stages:
The early stages of the Tawny Palmfly is polyphagous and feed on the leaves of a number of host plants in the Arecaceae (Palmae) family. Thus far, three of the local host plants haven been confirmed and identified (see list of host plants given earlier).

Host plant: Fish tail Palm.

A mother Tawny Palmfly laying an egg on the underside of a frond of the Fish Tail Palm.

The eggs of the Tawny Palmfly are laid singly on a leaf blade of the host palm tree, typically on the underside. Each white egg is nearly spherical with a diameter of about 1.5mm. Unlike the eggs of the Common Palmfly, the egg does not turn yellow as it develops.

Two views of an egg of the Tawny Palmfly.

Two views of a mature egg of the Tawny Palmfly.

The egg takes about 4-4.5 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 length of about 2.8mm. Its cylindrical body is pale whitish. The large head capsule is dark brown to black in color and has three pairs of prominent protuberances lining the perimeter with the apical pair being the largest and longest. Each protuberance ends with a thick setae bearing a transparent droplet at its tip. Rows of fine setae, also bearing terminal droplets, run along the length of the body dorso-laterally and laterally. A pair of long whitish processes occur at the posterior end of the body, each of which ends with a droplet-bearing black setae.

A newly hatched Tawny Palmfly caterpillar pausing next to its empty egg shell, length: 3mm.

Once the newly hatched moves on to feed on the young leaves, its body turns yellowish green in colour. Several contrasting longitudinal bands, pale yellowish in color and of varying widths, adorn the body surface dorso-laterally and laterally. This instar lasts 4-6 days with the length reaching up to 6.5-8mm.

Two views of 1st instar caterpillar, length:6.75mm.

The body of the 2nd instar caterpillar is similarly marked as in the late 1st instar. The most obvious change is in the head capsule where the three pairs of protuberances becomes longer and the setae they bear shorter. The apical pair also takes on a few short side branches. The pair of anal processes are longer proportionately and mostly black in coloration. Numerous short fine setae cover the body surface. Of the several yellowish bands running lengthwise, the dorso-lateral pair running up to the upperside of the anal processes becomes the most prominent of all. This instar lasts about 3-5 days with the body length reaching up to 11-13mm before the moult to the 3rd instar.

Head capsules: 1st instar (left) and 2nd instar (right).

Two views of a newly moulted 2nd instar caterpillar.

Two views of a 2nd instar caterpillar, length: 11mm

The 3rd instar caterpillar is similar in appearance to the 2nd instar caterpillar with the only obvious change being in the appearance of the head capsule. Small pale yellow patches appear laterally and apically on the head capsule which also has its two lower pairs of protuberances turn yellowish to orangy brown with their short terminal setae still brown to black in color. The yellow dorso-lateral longitudinal bands are enlarged slightly in each of abdominal segments. This instar takes about 4-5 days to complete with body length reaching about 18-20mm.

Two views of a newly moulted 3rd instar caterpillar.

Two views of a 3rd instar caterpillar, length: 20mm.

Retaining very much the same body features from the earlier two instars, the 4th instar caterpillar distinguishes itself in having a head capsule with proportionally longer apical protuberances (with the base of side protuberances in orangy brown) and larger lateral and frontal yellowish patches. The anal processes being mostly yellowish to salmon red in coloration. The nodal enlargement in the dorso-lateral yellow bands is also more pronounced in this stage. This instar lasts about 5 days with the body length reaching about 32-34mm.

Head capsules: 3rd instar (left) and 4th instar (right).

Two views of a 4th instar caterpillar, length: 25mm.

Two views of a 4th instar caterpillar, dormant before its moult, length: 33mm.

The 5th and final instar brings about another change in the appearance of the head capsule. Now white patches cover the frontal and middle area, stretching up into the two apical protuberances. The long and slender anal processes are mostly salmon red in coloration. The nodes in the dorso-lateral yellow band are much more prominent and could be rather large in certain specimens. A variable aspect of these nodes is that each node could be entirely yellow, or be adjoined with a dark green spot, or has a pale orange patch embedded in it.

Two views of a newly moulted 5th instar caterpillar, length: 31mm.

Head capsule of the 5th instar caterpillar.

Two views of a 5th instar caterpillar, length: 32mm.

Two views of another 5th instar caterpillar, length: 42mm.

The 5th instar lasts for 8-10 days, and the body length reaches up to 48-51mm. On the last day, the caterpillar ceases feeding, its body becomes shortened but with essentially no change in body color. It wanders around in search of a pupation site. Typically it comes to a halt on the underside of leaf blade (of the host plant) where the caterpillar spins a silk pad to which it attaches its graspers and then rests in a head-down posture.

Two views of a pre-pupa of the Tawny Palmfly in a head-down posture.

The pupation event of a Tawny Palmfly caterpillar.

Pupation takes place 1 day after the caterpillar assumes the haed-down posture. The green pupa has yellowish strips running on the dorsum of the thorax, dorso-laterally and laterally on the abdomen and the leading edges of the wing case. These yellow strips are outlined in a reddish to deep pink. The pupa also has a pair of short cephalic horns, and the dorsum of its thorax is sharply raised. Length of pupae: 20-24mm.

Two views of a pupa of the Tawny Palmfly.

Two views of a mature pupa of the Tawny Palmfly.

After about 7 days of development, the pupal skin turns translucent as the development within the pupal case comes to an end. The pupa is mostly black at this point. The following day, the adult butterfly emerges from the pupal case. It then perches on the pupal case or nearby to expand and dry its wings before taking its first flight.