30 May 2015

Life History of the Philippine Swift

Life History of the Philippine Swift (Caltoris philippina )


Butterfly Biodata:
Genus: Caltoris Swinhoe, 1893
Species: philippina Herrich-Schäffer, 1869
Sub-species: philippina Herrich-Schäffer, 1869
Wingspan of Adult Butterfly: 30-34mm
Caterpillar Local Host Plants: Bambusa_heterostachya (Poaceae; common name: Malay Dwarf Bamboo), Bambusa vulgaris (Poaceae, common names: Common bamboo, Buloh Minyak, Buloh Kuning).




Physical Description of Adult Butterfly:
The forewing is distinctly excavate at vein 2. On the upperside, the wings are dark brown. The forewing does not have any cell spots, but  there are  hyaline spots in spaces 2,3 and 4, subapical spots in spaces 6 and 7.  In addition,  the male has a pale yellow spot in the lower half of space 1b of the forewing. On the underside, the wings are unicolourous with a strong greenish tinge.

A male Philippine Swift with partially opened wings, showing the lack of forewing cell spots.

A male  Philippine Swift with partially opened wings, showing the arrangement of spots on the forewing upperside.

Field Observations of Butterfly Behaviour:
The Philippine Swift is rare in Singapore. Sightings typically took place in nature reserves or wastelands where clumps of bamboo are growing in the vicinity. The adults are usually seen perching on a leaf in a shady environment. At times, they have been observed to puddle on bird droppings.  





Early Stages:
The Philippine Swift has been bred on two bamboo spp., namely, Bambusa_heterostachya and Bambusa vulgaris. The caterpillars feed on leaves of these bamboo spp. and live in leaf shelters formed from cutting/folding leaf fragments.

Local host plant #1: Bambusa_heterostachya.

Local host plant #2: Bambusa vulgaris.

The eggs are laid singly on the upperside of a leaf of the host plant. Each hemi-spherical egg is whitish with a small reddish/orangy patch at the top where the micropyle  is situated. A number of very fine and obscure  striations running longitudinally from the micropyle to the base. The basal diameter is about 1.1mm.

Two views of an egg of the Philippine Swift.

It takes about 4.5-5 days for the egg to hatch. The young caterpillar eats just enough of the shell to emerge, and has a length of about 2.9mm. Its golden yellowish  body is cylindrical in shape and has a tuff of few moderately long setae at the posterior end. The head capsule is black. A black collar mark can be found the dorsum of the prothorax. The newly hatched nibbles away most of the egg shell remnant before proceeding to construct its first leaf shelter.

A newly hatched caterpillar eating its egg shell.

A newly hatched caterpillar in its very first leaf shelter. Further "stitching" work by the caterpillar will bring the two opposite edges together.

The body turns yellowish green after the caterpillar has a few sessions of the leaf diet. By the time the caterpillar lies dormant for its moult to the 2nd instar, its length has reached 5-5.5mm. The 1st instar takes a total of 3-3.5 days to complete.

Two views of a 1st instar caterpillar, length:4.5mm.

Two views of a 1st instar caterpillar, dormant prior to its moult, length:4.9mm.

The 2nd instar caterpillar has a yellowish green body, and the head capsule is still black. The black collar mark on the prothorax has faded to just to hint of its presence. This instar lasts about 3-4 days with the body length reaching about 8.5-9.5mm.

Two views of a 2nd instar caterpillar, early in this stage, length: 5mm.

Two views of a 2nd instar caterpillar, length: 6.5mm.

The 3nd instar caterpillar still has a black head capsule but its body is now whitish with a slight hint of yellowish green. There is no longer any trace of the black collar mark on the prothorax. This instar lasts a total of 3-4 days with the body length reaching about 14-15mm.

Two views of a 3rd instar caterpillar, early in this stage, length: 8mm.

Two views of a 3rd instar caterpillar, length: 11.5mm.

The 4th instar caterpillar resembles the 3rd instar caterpillar closely. In some specimens, the head capsule is no longer entirely black as pale brownish lateral patches can be observed. This penultimate instar lasts 4-5 days with the body length reaching up to 20-21mm.

Two views of a 4th instar caterpillar, early in this stage, length: 14mm.

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

As in the 4th instar, the 5th instar caterpillar has a whitish body with a yellowish green undertone. In a prominent change, its head capsule is now pale biege brown in ground colour but dark reddish brown along the periphery and various sulci (groove/furrow). Two reddish brown stripes rise from the adfrontal area, giving the appearance of a chinese character . The anal plate is unmarked as in the all previous instars. This final instar takes about 8-10 days to complete with the body length reaching 30-35mm.

Two views of a newly moulted 5th instar caterpillar, length: 20mm.

Two views of a 5th instar caterpillar, length: 30.5mm.

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

Towards the end of 5th instar, the body of the caterpillar shortens in length and body colour assumes a uniform shade of pale lime green. It seeks out the underside of a leaf blade and forms a shallow but half-open shelter with silk threads at both ends. The body excretes a moderate amount of white waxy material at this stage. Within the shelter, a silk girdle and a silk pad are then spun. Once the caterpillar attaches its claspers to the silk pad, it enters the dormant prepupatory phase which lasts about one day.

Two views of a dormant pre-pupa of the Philippine Swift.

The pupa secures itself with the silk girdle and with its cremaster attached to the silk pad. It has a short thorax, a rather long abdomen, a short and pointed rostrum. The marking-free body is lime green in the thorax and wing pads but more yellowish green in the abdomen. Length of pupae: 25-30mm.

Two views of a pupa of a male Philippine Swift, length: 25mm.

After 7-8 days, the pupa becomes mostly black in the thorax and wing pads as the development within comes to an end. The next day, the adult Philippine Swift emerges from the pupa.

A mature pupa of the Philippine Swift.

A newly eclosed Philippine Swift, resting on its pupation shelter.

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 by Horace Tan, Photos by Lemon Tea, Tan Ben Jin, Chng CK, Sunny Chir and Horace Tan

1 comment:

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