27 June 2015

Life History of the Common Hedge Blue

Life History of the Common Hedge Blue (Acytolepis puspa lambi)

Butterfly Biodata:
Genus: Acytolepis Toxopeus, 1927
Species: puspa Horsfield, 1828
Sub-species: lambi Distant, 1992
Wingspan of Adult Butterfly: 25-30mm
Caterpillar Local Host Plants: Combretum sundaicum (Combretaceae), Ventilago maingayi (
Rhamnaceae), Prunus polystachya (Rosaceae), Rosa hybrids (Rosaceae).

Physical Description of Adult Butterfly:
On the upperside, the male is shining blue with a black border widening to about 2mm at the forewing apex; and the female is pale shining blue with very broad black borders on both wings. On the underside, the wings are greyish white and have the usual black marginal spots and post-discal bands on both wings. In addition, each hindwing features several black spots in the basal half and one small black spot at the extreme base of space 7.

A sunbathing male Common Hedge Blue showing us its wing upperside.

Field Observations of Butterfly Behaviour:
This species is moderately common in Singapore. It is usually found in forested areas of the nature reserves but occasional sightings have been made in urban parks and gardens. They have been observed to sunbathe with open wings and puddle on damp forest paths.

Early Stages:
Four local host plants have been recorded so far for the Common Hedge Blue. Of these, Combretum sundaicum and Prunus polystachya can be found in many parts of the central catchment reserve. Caterpillars of the Common Hedge Blue feed on young leaves of the host plants and are typically found in the company of attending ants.

Local host plant #1: Combretum sundaicum.

Local host plant #2: Ventilago maingayi.

Local host plant #3: Prunus polystachya.

Eggs of the Common Hedge Blue are laid singly on a young leaf, a young shoot, or the flower buds of the host plant. The small pale green egg is discoid in shape and about 0.6mm in diameter, its surface covered with a reticulated pattern of intersecting ridges. The micropylar sits atop in the middle of the top surface.

A female Common Hedge Blue laying an egg on the underside of a young leaf of Combretum sundaicum.

A female Common Hedge Blue laying an egg on the flower bud of a rose plant.

An egg of the Common Hedge Blue.

The egg takes 3 days to hatch. The young caterpillar emerges after nibbling away sufficiently large portion of the egg shell. Measured at a length of about 1mm, its pale yellowish body is cylindrical in shape, sporting long fine setae (hair) dorso-laterally and laterally. It has a pale yellowish brown head capsule. The newly hatched feeds on the lamina of a young leaf. After about 2-3 days of growth and reaching a length of about 2mm, the caterpillar moults to the next instar.

Two views of a newly hatched caterpillar, length: 1mm.

Two views of a 1st instar caterpillar, early in this stage, length: 1.25mm.

A 1st instar caterpillar, late in this stage, length: 1.9mm.

The body of the 2nd instar caterpillar is covered with numerous short and whitish setae. Rows of longer white setae can be found dorsally and laterally. The body is pale yellowish brown to pale yellowish green. The prothoracic shield has the same coloration as the body base colour and thus indistinct. Meanwhile, the head capsule is still pale yellowish brown. This instar lasts about 3-4 days with the body length reaches up to 4mm.

Two views of a 2nd instar caterpillar, early in this stage, length: 2.9mm.

Two views of a 2nd instar caterpillar, late in this stage, length: 4mm.

Caterpillars of the Common Hedge Blue with ants in attendance on a leaf of Combretum sundaicum. Can you spot the three caterpillars?

The 3rd instar caterpillar resembles the 2nd instar caterpillar closely in having numerous short and fine setae all over the body. Short oblique whitish stripes are present on the body dorso-laterally. Their arrangement on the sides of the dorsum gives the impression of yellowish green dorsal band being present. Both the dorsal nectary organ (on the 7th abdominal segment) and tentacular organs (on the 8th abdominal segment) are now easily observed. The 3rd instar takes 3-4 days to complete with the body length reaching about 7-8mm.

Two views of a newly moulted 3rd instar caterpillar, eating its exuvia, length: 4mm.

Two views of a 3rd instar caterpillar, length: 4.5mm.

Two views of a late 3rd instar caterpillar, dormant prior to its moult, length: 6mm.

A caterpillar of the Common Hedge Blue with ants in attendance on a young shoot of Prunus polystachya.

The 4th (and final) instar caterpillar bears cose resemblance to its former self in the 3rd instar. The lateral oblique whitish markings and the dorsal band are more prominent in this instar. Depending on the coloration of the leaf it feeds on, the caterpillar could come in a pale green form, a pale yellowish brown form or a reddish brown form. The dorsal nectary organ is easily observed as a paler elliptical patch on the 7th abdominal segment.

Two 4th instar caterpillars, brown and green forms, length: 8mm.

Two views of another 4th instar caterpillar, length: 11mm.

Two views of yet another 4th instar caterpillar, reddish brown form, on young leaves of Ventilago maingayi, length: 12mm.

After about 4-5 days of growth and reaching a maximum length of around 14mm in the final instar, the body of the caterpillar gradually shrinks and decolorises. The caterpillar typically chooses to enter their pre-pupatory phase in tight pockets of space between leaves in leaf litter. At the chosen site, the caterpillar readies itself for pupation by spinning a silk girdle and a silk pad. The caterpillar secures itself to the silk pad via claspers at its posterior end.

Two early pre-pupae of the Common Hedge Blue.

Two views of a pre-pupa of the Common Hedge Blue.

Pupation takes place after one day of the pre-pupal stage. The pupa has the typical lycaenid shape. It is pale yellowish brown in base color with a fair number of brown and black specks of various sizes. The pupa has a length of about 8-9mm.

Two views of a pupa of the Common Hedge Blue.

Eclosion takes place after 5-6 days in the pupal stage. The mature pupa gradually darkens in colour the day before. Bluish patches on forewing upperside become clearly visible in the wing pads of the mature pupa, and the extent of blue coloration will now tell us the sex of the soon to emerge adult.

Two views of a mature pupa of a male Common Hedge Blue.

Two views of a mature pupa of a female Common Hedge Blue

  • [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 Jonathan Soong, Koh Cher Hern, Cai Jin Huang, Anthony Wong, Chng CK, Loke PY and Horace Tan

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