Life History of the Besta Palm Dart

Life History of the Besta Palm Dart (Telicota besta bina)

Butterfly Biodata:
Genus: Telicota Moore, 1881
Species: besta Evans, 1949
Sub-species: bina Evans, 1949
Wingspan of Adult Butterfly: 39-48mm
Caterpillar Local Host Plants: Ischaemum muticum (Poaceae; common name: Seashore Centipede Grass), Scleria bancana (Cyperaceae; common name: Winged Scleria).

A female Besta Palm Dart.

A male Besta Palm Dart.

A view of the upperside of a male Besta Palm Dart, showing the male brand.

Physical Description of Adult Butterfly:

On the upperside, the wings are black with an orange post-discal band on the forewing running from the dorsum and bent over at vein 6 to continue along the costal margin. The orange-yellow post-discal band on the hindwing runs from vein 1b to space 6. The veins crossing the orange-yellow bands on both wings are black-dusted. The male has a grey brand from about the middle of vein 1b to vein 4 on the forewing. The brand is located nearer to the inner edge of the black discal fascia than to tis outer edge. On the underside, the wings are ochreous with post-discal bands outlined with black. The female is greenish ochreous on the hindwing.

A female Besta Palm Dart.

A view of the upperside of a female Besta Palm Dart.

Field Observations of Butterfly Behaviour:

The Besta Palm Dart is moderately common in Singapore. The adults are strong flyers and are typically sighted along the forest edge amongst the grassy undergrowth. The swift flying adults have been observed to visit flowers and sunbath with open-wings in sunny weather.

Early Stages:

Locally in Singapore, Besta Palm Dart has thus far been observed to utilize a common grass species, Ottochloa nodosa, and a moderately common sedge species Scleria bancana as larval food plants. The caterpillars feed on leaves of the host plant in all instars and live in leaf shelters. As the caterpillar grows in size through progressing instars, it migrates to ever larger shelters constructed by joining cut leaf fragments or the opposite edges of a single blade.

Local host plant #1: Ischaemum muticum.

Local host plant #2: Scleria bancana.

A leaf shelter of the Besta Palm Dart observed in the field.

The eggs are laid singly on a leaf blade of the host plant, typically on the underside. Each dome-shaped egg is creamy white and appears to be smooth to the naked eyes. A closer inspection reveals numerous short, discontinuous and irregular tiny ridges running in a longitudinal direction. Each egg has a diameter of about 1.1mm.

An egg of the Besta Palm Dart laid on the underside of a leaf blade.

Two views of an egg of the Besta Palm Dart, diameter: 1.1mm.

It takes about 4 days for the egg to hatch. The young caterpillar eats just enough of the shell to emerge, and then immediately proceeds to finish the remaining egg shell. The newly hatched has a length of about 2.9mm. Its pale yellowish body is cylindrical in shape with a small number of very short and tiny dorso-lateral and lateral setae. There is a tuff of long setae on the posterior segment. It has a black head and a black collar on the prothorax

Two views of a mature egg with a portion of the egg shell already eaten.

Two views of a newly hatched caterpillar eating its egg shell.

Two views of a 1st instar caterpillar, early in this intar, length: 2.9mm.

After consuming the egg shell, the newly hatched caterpillar constructs its first leaf shelter,  typically at the tip of a leaf blade. The body takes on a dark undertone after a few feeding sessions on the leaf. The 1st instar takes a total of 4 days to complete with body length reaching about 6mm.

Two views of a 1st instar caterpillar, length: 4.8mm.

A late 1st instar caterpillar, dormant prior to its moult, length: 5.8mm.

The body of the 2nd instar caterpillar resembles that of the first instar, but with the dark collar on the prothorax now vaguely present. The setae at the posterior end are now proportionately shorter and the anal plate takes on a greyish coloration. The body colour is mainly yellowish green with a dark green undertone. This instar lasts about 4 days with the body length reaching up to 10mm.

Two views of a 2nd instar caterpillar, early in this stage.

Two views of a 2nd instar caterpillar, length: 7.8mm.

The 3nd instar caterpillar resembles the 2nd instar caterpillar except for a more yellowish green body colour and the nearly indistinguishable collar mark on the prothorax. In contrast, the anal plate is now marked prominently in black. This instar lasts a total of 3-4 days with the body length reaching about 15mm.

Two views of a 3rd instar caterpillar, early in this stage, length: 9.8mm.

Two views of a 3rd instar caterpillar, length: 11mm.

Two views of a late 3rd instar caterpillar, dormant prior to its moult, length: 14.5mm.

The 4th instar caterpillar resembles the 3rd instar caterpillar closely. In some specimens, the head capsule has pale grey or brown lateral patches which are rather indistinct. This instar lasts 5-6 days with the body length reaching about 23-24mm.

Two views of a newly moulted 4th instar caterpillar.

Two views of a 4th instar caterpillar, length: 20mm.

Two views of a late 4th instar caterpillar, dormant prior to its moult, length: 23mm.

The 5th instar brings along a prominent change in the head capsule which now has two large pale brown lateral patches separated by dark band lining the epicranial suture. The body is now predominantly yellow with a a green undertone. The black marking on the anal plate has been observed to vary in size and shape among different specimens.

A newly moulted 5th instar caterpillar, length: 21.5mm.

Two views of a male 5th instar caterpillar, length: 26.5mm.

The 5th instar takes about 10-11 days to complete with the body length reaching up to 34-36mm, In the last day of this instar, the body gradually shorten and changes colour to beige purplish brown. The caterpillar ceases feeding and whitish powdery substance begin to appear on its ventrum. Next it proceeds to seal the shelter it is in with silk threads. Soon the caterpillar becomes dormant in this pupation shelter. This prepupatory phase lasts for about 1 day.

Two views of a 5th instar caterpillar, late in this stage, length: 31mm.

A pupation shelter opened to reveal  a pre-pupa of The Besta Palm Dart.

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, a rather long abdomen, and a few tuffs of setae at the anterior segment. The body is dark brown in the thorax and wing pad areas, but orangy brown in the abdomen. Length of pupae: 22-23mm.

Two views of a pupa of the Besta Palm Dart, length:22mm.

Close up views of the anterior end of a pupa of the Besta Palm Dart.

After 9 days, the pupa becomes dark brown with the thorax and wing pads mostly black. The orange markings present on the forewing upperside are now visible through the now translucent pupal skin. Eclosion takes place the next day.

Two views of a mature pupa of the Besta Palm Dart.

A newly eclosed Besta Palm Dart.

References:

• [C&P4] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, Malayan Nature Society, 1992.
• 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.

Text and Photos by Horace Tan.