Life History of the Tree Flitter

Life History of the Tree Flitter (Hyarotis adrastus praba)

Butterfly Biodata:
Genus: Hyarotis Moore, 1881
Species: adrastus Stoll, 1780
Sub-species: praba Moore, 1865
Wingspan of Adult Butterfly: 34-38mm
Caterpillar Local Host Plant: Daemonorops augustifolia (Arecaceae; common name: Water Rattan Palm).

Physical Description of Adult Butterfly:

Above, the wings are dark brown with the forewing adorned with white hyaline spots in the cell-end and spaces 2, 3, subapical spots in spaces 6,7 and 8, and another in space 1b. Underneath, the wings are dark brown with an irregular white discal fascia on the hindwing. The cilia are chequered on both wings. The antenna has a white patch below the apicus.

A sun-bathing Tree Flitter.

A newly eclosed Tree Flitter with partially open wings.

A Tree Flitter taking nectar from Syzygium flowers.

Field Observations of Butterfly Behaviour:

The Tree Flitter is moderately rare in Singapore. Infrequent sightings are restricted to the edges of the nature reserve and at times in urban parks and gardens. The adults are fast flyers and zipped around rapidly at close to ground level most of the time. They have been observed to visit flowers and sunbath in sunny weather, and to puddle on bird dropping.

A Tree Flitter taking nectar from a flower of Asystasia gangetica.

A Tree Flitter taking nectar from an Ixora flower.

A Tree Flitter taking minerals from bird dropping.

Early Stages:

Across its wide range of distribution in Asia, the Tree Flitter is known to be polyphagous. So far only one local host plant, Daemonorops augustifolia, has been established for the Tree Flitter. This rattan palm is widely distributed in the nature reserve.

Local host plant: Daemonorops augustifolia.

The caterpillars of the Tree Flitter feed on leaves of the host plant in all instars, and conceal itself in leaf shelters between feeding sessions. In all instars, the caterpillar constructs its shelter on a leaflet by spinning multiple transverse silk threads to create a trough-like cavity, and then securing an adjacent leaflet over it for concealment. The caterpillar ventures out of this shelter periodically to feed on the lamina of both leaflets involved.

The leaf shelter of a 2nd instar Tree Flitter caterpillar found in the field.

The eggs are laid singly on the upper surface of a leaflet of the host plant. Each shallow dome-shaped egg is golden yellow initially but small reddish, irregularly shaped patches appear on the 2nd day. Numerous shallow longitudinal ridges emanating from the micropylar sitting atop. The egg is rather large with a diameter of about 1.3mm.

A far view of an egg of the Tree Flitter laid on the upperside of a leaflet.

Two views of an egg of the Tree Flitter, diameter: 1.3mm.

It takes 4-5 days for the egg to hatch. The egg decolorsies to milky white when fully mature on the last day of this phase. The young caterpillar eats just enough of the shell to emerge, and it proceeds to nibble away the remaining egg shell after that. The newly hatched has a length of about 3mm. Its pale yellowish body is cylindrical in shape and a tuff of moderately long white setae can be found on the posterior end. Its head is black and adjoined with a black collar mark on the dorsum of the prothorax.

A sequence of three views showing the mature egg (left), larval head through hole (center) and remnant of the egg shell.

A Tree Flitter caterpillar emerges from its egg shell.

Two views of a newly hatched caterpillar of the Tree Flitter, length: 3mm.

After consuming the egg shell, the newly hatched caterpillar constructs its first leaf shelter typically on the underside of the same leaflet of the palm frond. Its body takes on a strong green undertone after a few feeding sessions on the leaf. The 1st instar takes a total of 5-6 days to complete with body length reaching about 6.5mm.

Two views of a 1st instar caterpillar, late in this stage, length: 6.2mm.

A late 1st instar caterpillar, dormant prior to its moult, length: 6.2mm.

The unmarked body of the 2nd instar caterpillar is pale yellowish with a strong green undertone. The head capsule is now dark brown, and the black collar mark is no longer present. Those long setae present on the posterior segment in the 1st instar are replaced by short setae. This instar lasts a total of 5-6 days with the body length reaching 9-10mm.

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

Two views of a 2nd instar caterpillar, length: 8.5mm.

A late 2nd instar caterpillar, dormant prior to its moult, length: 9mm.

The 3nd instar caterpillar resembles the 2nd instar caterpillar closely. In some specimens, the dark brown head capsule shows signs of slight decolorisation to a paler shade of brown laterally. This instar lasts a total of 5-6 days with the body length reaching 15-20 mm.

Two views of a 3rd instar caterpillar, newly moulted, length: 10mm.

Two views of a 3rd instar caterpillar, length: 12mm.

A late 3rd instar caterpillar, dormant prior to its moult, length: 15mm.

The 4th (penultimate) instar caterpillar typically has its dark brown head capsule adorned with large pale brown lateral patches. Its body has two faint and whitish dorso-lateral bands running lengthwise. This penultimate instar lasts 6-7 days with the body length reaching 26-28mm.

Two views of a 4th instar caterpillar, early in this stage, length: 19mm.

Two views of a 4th instar caterpillar, length: 24mm.

A late 4th instar caterpillar, dormant prior to its moult, length: 26mm.

The leaf shelter of a 4th instar caterpillar observed in the field.

The body of the 5th instar caterpillar appears to be more whitish than in the earlier instars. Both dorso-lateral whitish bands are now broader and more prominent. The most drastic change going into the final instar is in the head capsule which has become mostly pale biege brown marked with a pale brown or dark brown stripe on both sides of the coronal sulcus. In some specimens, the periphery of the head capsule is outlined in dark brown. The 5th instar takes about 9-10 days to complete with the body length reaching up to 38-40mm.

Two views of a newly moulted 5th instar caterpillar, with hardly noticeable lateral brown stripes on the head, length: 28.5mm.

Two views of another 5th instar caterpillar, late in this stage, length: 34mm.

Another final instar caterpillar with its lateral stripes on the head in dark brown to black.

In the last day of the final instar, the caterpillar seeks out a new site on the underside of a leaflet to construct its pupation shelter. At this stage, its body changes color to beige brown with a purplish/pinkish undertone, and a moderate amount of whitish powdery substance is excreted to line the inner surface of the shelter. The semi-open shelter is simply a trough constructed with two to three transverse silk bands bringing the two edges sufficiently close (but not together). Unlike the shelters used earlier, the pupation shelter is not concealed with another leaflet secured over the exposed area. The caterpillar enters the immobile pre-pupatory phase once it has constructed a short transverse silk band near the posterior end and a silk girdle across its anterior abdominal segments. This prepupatory phase lasts about 1 day.

A sequence of three views: early pre-pupa (top), immobile pre-pupa (middle) and fresh pupa (bottom) of a Tree Flitter caterpillar.

The pupation event of a Tree Flitter caterpillar.

Pupation takes place within the leaf shelter. The pupa is secured with the silk girdle and a cremastral attachment to the short transverse silk band constructed during the early pre-pupal phase. Its body is bright yellowish brown adorned with a dorsal series of small dark spots flanked by two series of short yellowish streaks. Further out, there is a dorso-lateral series of yellowish steraks. The body surface is also coverd with numerous small brown specks. The pupa has a short thorax, a rather long abdomen, and a long pointed rostrum. Length of pupae: 30-32mm.

Two views of a pupa of the Tree Flitter.

After 7.5-8 days, the pupa becomes mostly black as the adult development stage within its case comes to an end. Eclosion takes place the next day.

Two views of a mature pupa of the Tree Flitter.

A newly eclosed Tree Flitter resting near its pupal case.

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 Photographic Monograph on Hong Kong's Butterflies, Volume 1, Hong Kong Lepidopterists' Society, pages 18-19, 2007.
• A Field Guide to the Butterflies of Singapore, Khew S.K., Ink On Paper Communications, 2010.

Text by Horace Tan, Photos by Bobby Mun, Koh Cher Hern, Loke PF, Nelson Ong, Anthony Wong, Federick Ho, Khew SK and Horace Tan.

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