Life History of the Bamboo Paintbrush Swift

Life History of the Bamboo Paintbrush Swift (Baoris farri farri)

Butterfly Biodata:
Genus: Baoris Moore, 1881
Species: farri Moore, 1878
Sub-species: farri Moore, 1878
Wingspan of Adult Butterfly: 36-40mm
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:

On the upperside, the wings are dark brown. The forewing has hyaline spots in spaces 2-4, 6-8 and 2 cell spots. The female is usually fully spotted and has an additional non-hyaline spot in space 1b on the forewing. The hindwing does not bear any spot, but the male has a black hair tuft in the cell on top of a scent pouch (hence "Paintbrush" in its common name). On the underside, the wings are pale brown and similarly ``spotted'' as per the upperside.

Field Observations of Butterfly Behaviour:

The Bamboo Paintbrush Swift is moderately rare in Singapore. Sightings typically took place in parks, urban gardens and forested areas where clumps of bamboo are growing in the vicinity. The swift-flying adults are relatively large and have been observed to vist flowers for nectar and perching on leaves to sunbathe in sunlit conditions.

Early Stages:

The Bamboo Paintbrush Swift has been bred on two bamboo spp., namely, Bambusa heterostachya and Bambusa vulgaris. Several other bamboo species, yet to be identified, also serve as the larval host plants. 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 dome-shaped egg is whitish with a small reddish patch at the top where the micropyle is situated. The basal diameter is about 1.8-1.9mm.

Two views of an egg of the Bamboo Paintbrush Swift.

It takes about 4-5 days for the egg to hatch. The young caterpillar eats just enough of the shell to emerge, and has a length of about 3-3.2mm. Its pale 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.

Two views of a mature egg of the Bamboo Paintbrush Swift with the larval head visible through the hole.

A newly hatched caterpillar in its very first leaf shelter.

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 6-6.5mm. The 1st instar takes about 4-5 days to complete.

Two views of a 1st instar caterpillar, length:5.1mm.

A late 1st instar caterpillar, dormant prior to its moult, length:6.3mm.

The 2nd instar caterpillar has a pale yellowish green body, and the head capsule is still black. The black collar mark on the prothorax has faded to become almost indistinguishable. This instar lasts about 3-4 days with the body length reaching about 9.5-10.5mm.

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

Two views of a 2nd instar caterpillar, length: 8.8mm.

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, newly moulted.

Two views of a 3rd instar caterpillar, length: 14.8mm.

The 4th instar caterpillar resembles the 3rd instar caterpillar closely. The body appears to be more whitish than that of the 3rd instar. This penultimate instar lasts 4-5 days with the body length reaching up to 24-25mm.

Two views of a newly moulted 4th instar caterpillar, length: 13.8mm.

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

As in the 4th instar, the 5th instar caterpillar has a whitish body with a slight yellowish green undertone. In a prominent change, its head capsule is now mainly white but black along the periphery and various sulci (groove/furrow). Two bold and black stripes rise from the adfrontal area. The anal plate is unmarked as in the all previous instars. This final instar takes about 6-7 days to complete with the body length reaching 40-41mm.

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

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

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 and a half day.

A dormant pre-pupa of the Bamboo Paintbrush 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 moderately long. The marking-free body is lime green in the thorax and wing pads but more yellowish green in the abdomen. Length of pupae: 33-36mm.

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

Two views of a mature pupa of the Bamboo Paintbrush Swift.

Six to seven days later, the pupa turns mostly black and forewing spots are noticeable in the wing pads. The next day, the adult emerges from the pupa.

A newly eclosed Bamboo Paintbrush Swift.

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 Frederick Ho, Koh Cher Hern and Horace Tan