Life History of the Pale Fourline Blue

Life History of the Pale Fourline Blue (Nacaduba hermus swatipa)

Butterfly Biodata:
Genus: Nacaduba Moore, 1881
Species: hermus C. Felder, 1860
Subspecies: swatipa Corbet, 1938
Wingspan of Adult Butterfly: 27-30mm
Caterpillar Local Host Plant: Barringtionia racemosa (Lecythidaceae, common name: Common Putat, Fish-Killer Tree, Fish-Poison Tree, 水茄笗, 玉蕊).

A female Pale Fourline Blue resting on a flower of Bidens alba (Spanish Needle).

A male Pale Fourline Blue resting on a flower of Tridax procumbens (Coat Buttons).

A female Pale Fourline Blue visiting inflorescence of Leea indica (Bandicoot Berry).

Physical Description of Adult Butterfly:

As a member of the pavana group, the adult does not have a basal pair of lines in the underside forewing cell. Above, the male is violet blue (with a slightly frosted appearance) with a thread-thin border; the female is pale shining blue with broad brown borders. Underneath, both sexes are greyish brown with the bands (post-discal, discal and basal) composed of a double series of whitish striae inwardly lined with dark striae. Forewing postdiscal band is usually not dislocated at vein 6. On each hindwing, there is an orange-crowned tornal spot in space 2 lightly speckled with bluish-green metalic scales. Next to the tornal spot, a pair of filamentous white-tipped tails occurs at end of vein 2. Marginal and submarginal spots are dark greyish brown, and submarginal spots are mostly broadly lunulate. In the hindwing, the postdiscal band is usually close to the submarginal band.

A male Pale Fourline Blue resting on a tree trunk in a nature park.

A male Pale Fourline Blue showing its violet blue upperside.

A male Pale Fourline Blue resting on a broken stem.

A male Pale Fourline Blue feedinig on a flower of Tridax procumbens (Coat Buttons).

Field Observations of Butterfly Behaviour:

The Pale Fourline Blue was recorded by early researchers in Singapore, but the species has been rarely sighted in the past two decades. However, in the second half of this year, sightings have increased markedly, thanks to the keen eyes of a few devoted young naturalists. These recent sightings are confined to the central and northern parts of the Singapore island where the local host plant, Barringtonia racemosa, is growing in abundance. The adults have been seen flying in the vicinity of the host plant, visiting flowering plants, puddling on wet grounds and performing oviposition rituals at developing inflorenscences of the host plant.

A male Pale Fourline Blue resting on a tree trunk in a nature park.

A Pale Fourline Blue checking out a flower bud of Barringtonia racemosa.

A female Pale Fourline Blue perching on a leaf surface in a nature park.

Another female Pale Fourline Blue perching on a leaf surface in a nature park.

Early Stages:

The Pale Fourline Blue is polyphagous. In other countries/regions, plants such as Entada rheedii, Embelia subcoriacea and Nephelium lappaceum have been recorded as larval hosts. However, for Singapore, only one local host plant, Barringtonia racemosa, has thus far been recorded. The caterpillars of the Pale Fourline Blue mainly feed on flower buds of Barringtonia racemosa, but at times, also feed on the rachis and pedicel of the inflorescence. As in the case for most lycaenidae species, the caterpillars of the Pale Fourline Blue are tended by a number of ant species.

Local host plant: Barringtonia racemosa. Left: leaves in clusters. Right: an inflorescence bearing flower buds.

A mother Pale Fourline BLue ovipositing on a flower bud of Barringtonia racemosa.

A mother Pale Fourline BLue ovipositing on a young flower bud of Barringtonia racemosa.

Eggs are laid singly on a flower bud or the rachis of an inflorescence of Barringtonia racemosa. It is not uncommon for a number of eggs to be found in the same inflorescence. Each egg is whitish with a green undertone. It has a thick discoid shape, and features a depressed micropylar on top. The egg surface is finely reticulated, slightly raised at the intersections of criss-crossing ridges. Th egg has a diameter of about 0.5mm.

Eggs on flower buds of Barringtonia racemosa.

Two views of an egg of the Pale Fourline Blue.

It takes about 3 days for the egg to hatch. The young caterpillar consumes part of the egg shell to emerge. With a length of about 0.9mm, it has a pale yellowish body with long setae (hairs) dorsally and sub-spiracularly. The head is black in colour in this instar. The body color changes gradually to a brighter shade of yellow as growth progresses. The first instar lasts for 2-3 days and the body length reaches about 1.8mm before the moult to the 2nd instar.

Two views of a newly hatched caterpillar having its few meal on a flower bud

Two views of a 1st instar caterpillar, length: 1.1mm.

An early 1st instar caterpillar exploring a flower bud. Inset: a close-up view.

Two views of a 1st instar caterpillar, late in this stage, length: 1.8mm.

In the second instar, dorsal setae are much shortened proportionately compared to those in the first instar. Moreover, there are numerous short setae present all over the body surface. The body color is mainly yellow with a hint of reddish brown in the anterior and posterior segments. In some individuals, the pale reddish brown coloration is more extensive. The 2nd instar lasts for 2-3 days and the caterpillar grows to a length of about 3.3mm to 3.5mm.

Two views of a 2nd instar caterpillar, freshly moulted to this instar.

Two views of a 2nd instar caterpillar, early in this instar, length: 1.9mm.

Two views of a 2nd instar caterpillar, length: 3.4mm.

A 2nd instar caterpillar observed in the field feeding on a flower bud.

A 2nd instar caterpillar observed in the field with an ant attending to it.

Two views of a 2nd instar caterpillar, dormant prior to its moult.

As in the 2nd instar, the 3rd instar caterpillar is yellowish with varying extent of pale reddish brown coloration on body segments. In most individuals, the pale reddish hue is present in the thoracic segments and the last 4-5 abdominal segments, as well as in the dorsum of first 4-5 abdominal segments. The prothoracc shield is whitish in color. The dorsal nectary organ and tentacular organs are also easily discernible. After 3 to 4 days in this instar with the body length reaching about 6.8-7mm, the next moult brings the caterpillar to its final instar.

Two views of a newly moulted 3rd instar caterpillar, feeding on its exuvia.

Two views of a 3rd instar caterpillar, length: 3.5mm.

Two views of a 3rd instar caterpillar, length: 5.9mm.

Two views of a 3rd instar caterpillar, dormant prior to its moult.

A 3rd instar caterpillar with an attending ant in the field.

The 4th instar caterpillar are similar to the 3rd instar caterpillar but with all red and reddish brown patches much more prominently marked and in strong contrast to the ground color. Some individuals can even be entirely reddish brown to pinky red in all body segments. As in the 3rd instar, the prothorcic shield is whitish and the dorsal nectary organ and tentacular organs are prominent on the posterior segments. Tentacular organs are readily everted when the caterpillar senses a threat (such as from a competing caterpillar) or when attending ants are present.

Two views of a newly moulted 4th instar caterpillar, with exuvia yet to be eaten.

Two views of a 4th instar caterpillar, length: 7.8mm.

A 4th instar caterpillar attended by several ants in a nature park.

Two views of a 4th instar caterpillar, length: 12mm.

Two views of a red-form 4th instar caterpillar, length: 13mm.

A 4th instar caterpillar attended by a large ant.

The 4th instar lasts for 3-4 days and the body grows up to a length of about 13-13.5mm. On the last day of this stage, the caterpillar ceases food intake and its body shrinks in length and decolorises to a dull shade of yellowish to pinky brown. The fully grown caterpillar finally comes to rest on a spot among leaves where it readies the site for pupation by spinning a silk pad and a silk girdle to secure itself.

Two views of a 4th instar caterpillar, late in this stage, with color change taken place.

Two views of a girdled-down pre-pupa of the Pale Fourline Blue.

About 0.75 day later, pupation takes place. The pupa has the typical lycaenid form, and is 9.6-10.2mm in length. It is mostly yellowish brown and speckled with black spots of various sizes and shapes.

Two views of a pupa of the Pale Fourline Blue

Four to five days later, the pupa becomes darkened in color signaling the imminent emergence of the adult. The markings on the forewing upperside becomes increasing obvious through the pupal skin. The next day the adult butterfly emerges from the mature pupa.

Two views of a mature male pupa showing the extensive purplish blue coloration in the wing pad.

Two views of a mature female pupa showing the much less extensive bluish coloration in the wing pad.

A newly eclosed male Pale Fourline Blue.

A newly eclosed female Pale Fourline Blue.

References:

• [C&P5] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, G. and N. van der Poorten (Eds.), 5th Edition, Malayan Nature Society, 2020.
• Butterflies of Thailand, Pisuth Ek-Amnuay, 2nd Edition, 2012.
• Kawthankar N, Nitin R, Balakrishnan VC, Churi PV, Kalesh S, Satya Prakash & Kunte K (2023) Larval host plants and other hosts of Indian butterflies. In Kunte K, Sondhi S & Roy P (eds.). Butterflies of India, v. 4.12. Indian Foundation for Butterflies. https://www.ifoundbutterflies.org/larval-hosts.

Text by Horace Tan, Photos by Sebastian Ow, Zick Soh, Low JK, Khew SK  and Horace Tan.

Life History of the Jewelled Grass Blue

Life History of the Jewelled Grass Blue (Freyeria putli)

Butterfly Biodata:
Genus: Fryeria Courvoisier, 1920
Species: putli Kollar, 1844
Wingspan of Adult Butterfly: 12-16mm
Caterpillar Local Host Plant: Indigofera spicata (Fabaceae, common name: Creeping Indigo).

A Jewelled Grass Blue resting on an inflorescene of the Creeping Indigo.

A Jewelled Grass Blue resting on an inflorescene of the Creeping Indigo.

A Jewelled Grass Blue resting on a leaflet of the Creeping Indigo.

Physical Description of Adult Butterfly:
With a wing span of only 12-16mm, the Jewelled Grass Blue is a small and tailess butterfly, easily overlooked by casual observers. On the upperside, both sexes are dark brown with a row of black marginal spots in the hindwing. On the underside, both wings are gray to pale brown in ground colour, and feature brown cell-end bars. On the forewing, there is a post-discal series of white-bordered spots and a submarginal series of white-bordered spots. Each hindwing has a row of prominently orange-crowned marginal spots speckled with shining metallic scales. There is also a series of white-bordered post-discal spots, a white-bordered black costal spot, four transverse black subbasal spots and one small black basal spot in space 1.

A sunbathing Jewelled Grass Blue showing its brown upperside.

A Jewelled Grass Blue resting on an inflorescene of the Creeping Indigo.

A Jewelled Grass Blue feeding on a flower of the White Heads.

Field Observations:
The Jewelled Grass Blue was recently recorded in early September this year by local naturalist Fiora Li. Although the species is extant across a wide region ranging from India, Hong Kong, Taiwan and even to Australia, it has never been observed previously in Singapore. A small population was observed to be flying and breeding in an open grassy field where the host plant, the Creeping Indigo (Indigofera spicata), is growing in abundance. The adult butterflies typically fly at a low height above ground, feeding on flowers of the host plant as well as those of other weeds such as the White Heads (Eclipta prostrata) and Coat Buttons (Tridax procumbens). The male has also been observed to puddle on wet grounds in the same field.

A Jewelled Grass Blue puddling on a mud trail.

A Jewelled Grass Blue feeding on a tiny flower.

A Jewelled Grass Blue feeding on a flower of the Coat Buttons.

Early Stages:

A video clip showing the adult and immature stages of Jewelled Grass Blue.

Thus far, only one plant, Indigofera spicata (Creeping Indigo), has been recorded as the local host plant for the Jewelled Grass Blue. In other countries/regions, the larval host plants also include other Indigofera species, and a number of species in other plant families. The caterpillars of the Jewelled Grass Blue feed on flowers and leaves of the Creeping Indigo, with a strong preference for the former.

Local host plant: Indigofera spicata (Creeping Indigo).

A mating pair of Jewelled Grass Blue.

A mother Jewelled Grass Blue attempting to oviposit on an inflorescence of the Creeping Indigo.

A mother Jewelled Grass Blue ovipositing on an inflorescence of the Creeping Indigo.

A mother Jewelled Grass Blue resting on an inflorescence of the Creeping Indigo where an egg has earlier been oviposited.

The mother butterfly lays her eggs singly on the host plant, either among young floral buds on a developing inflorescence or on the surface of a young leaflet. Each greenish egg is about 0.5mm in diameter. It is discoid-shaped with a depressed micropylar at the center of the upper surface. The egg surface is reticulated with a fine pattern of whitish ridges and indentations.

Two views of an egg of the Jewelled Grass Blue laid on leaf surface.

Two views of an egg of the Jewelled Grass Blue laid among floral buds. Left: a few hours after oviposition. Right: a few hours before hatching.

It takes about 2 to 2.5 days for the egg to hatch. The newly hatched has a pale yellowish body with a length of about 0.7-0.8mm. The body also features long setae dorso-laterally and along body fringe. Its head capsule is black in color, and will remain so for all four instars. Depending on the oviposition site, the young caterpillar either feeds on the floral buds or the leaf lamina of leaflets near the empty egg shell. After about 1.5-2 days of growth in the first instar, and reaching a length of about 1.6mm, the caterpillar moults to the next instar.

A newly hatched caterpillar of the Jewelled Grass Blue after it emerges from the egg shell.

Two views of a 1st instar caterpillar feeding on a floral bud, length: 1.2mm.

Two views of a late 1st instar caterpillar, dormant prior to its moult.

In the 2nd instar, besides the long setae which occur dorso-laterally and along body fringe, there are short and fine setae covering the body surface, and tiny black spots scattered across the body surface. The caterpillar is yellowish or greenish. Whitish and narrow intermittent bands occur dorsally, dorso-laterally and sub-spiracularly. The 2nd instar caterpillar reaches a length of about 2.5-2.6mm, and after about 1.5-2 days in this stage, it moults again.

Two views of a newly moulted 2nd instar caterpillar, lying next to its exuvia.

Two views of a 2nd instar caterpillar feeding on a floral bud, length: 1.7mm.

Two views of a 2nd instar caterpillar feeding on a leaflet, length: 2.4mm.

Two views of a late 2nd instar caterpillar, dormant prior to its moult, length: 2.2mm.

Compared to the 2nd instar caterpillar, the 3rd instar caterpillar bears a denser coat of proportionately shorter setae on its body. The body could be pale yellowish green entirely or featuring reddish shading dorsally and along body fringe. The dorsal nectary organ and the pair of tentacular organs, on the 7th and 8th abdominal segments, are now readily observed. The 3rd instar takes about 1.5 to 2 days to complete with the body length reaching about 5-5.3mm.

Two views of a newly moulted 3rd instar caterpillar, exiting from its old larval skin.

Two views of a 3rd instar caterpillar with reddish markings, length: 3mm.

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

Two views of a late 3rd instar caterpillar with reddish markings, dormant prior to its moult, length: 4.5mm.

Two views of another late 3rd instar caterpillar, dormant prior to its moult, length: 5mm.

While having similar body markings as in the 3rd instar, the 4th instar caterpillar has a more distinctive appearance, featuring a dense coat of short whitish setae all over the body surface. The body coloration could be entirely greenish or pale yellowish green with reddish dorsal and sub-spiracular bands.

Two views of a 4th instar caterpillar with reddish markings feeding on floral buds, early in this stage, length: 5.5mm.

A 4th instar caterpillar of the Jewelled Grass Blue feeding on a leaflet.

Two views of a 4th instar caterpillar of the Jewelled Grass Blue with reddish markings feeding on floral buds, late in this stage, length: 9.8mm.

Two views of a 4th instar caterpillar of the Jewelled Grass Blue with reddish markings, late in this stage, length: 9.5mm.

After about 2-2.5 days of feeding and reaching a length of about 9.5-10mm, the caterpillar stops feeding and seeks out a pupation site. During this time, its body gradually shortened and markings decolorised to pale greenish. Typically the caterpillar chooses a leaflet of the host plant, on either side for its pupation site. The pre-pupatory caterpillar prepares for pupation by spinning a silk girdle and a silk pad to which it attaches itself via anal claspers.

Two views of a pre-pupa of the Jewelled Grass Blue on the uperside of a leaflet.

After about 0.75-1 day as a pre-pupa, pupation takes place. The fresh pupa is predominantly yellowish green to green. It has a typical shape of a lycaenid pupa. With the exception of the wing pads, there are long whitish fine setae on the entire pupal body. Pupal length: 6.8-7.2mm.

Two views of a pupa of the Jewelled Grass Blue.

Four days later, the pupa starts to turn black, first in the wing pad and thorax, then progressively in the abdomen. The next day, the pupal stage comes to an end (pupal period: 5 days) with the emergence of the adult butterfly.

Two views of a mature pupa of the Jewelled Grass Blue on the underside of a leaflet of the host plant.

A newly eclosed Jewelled Grass Blue.

References:

• Butterflies of Thailand, Pisuth Ek-Amnuay, 2nd Edition, 2012.
• A Photographic Monograph on Hong Kong Butterflies, Volume 3, p.388, Hong Kong Lepidopterists' Society.
• Li FY (2023) Biodiversity Record: New record of the butterfly, Freyeria putli, in Singapore. Nature in Singapore, 16: e2023102. DOI: 10.26107/NIS-2023-0102.
• Kawthankar N, Nitin R, Balakrishnan VC, Churi PV, Kalesh S, Satya Prakash & Kunte K (2023) Larval host plants and other hosts of Indian butterflies. In Kunte K, Sondhi S & Roy P (eds.). Butterflies of India, v. 4.12. Indian Foundation for Butterflies. https://www.ifoundbutterflies.org/larval-hosts.

Text by Horace Tan, Photos by Koh Cher Hern, Sebastian Ow, Zick Soh, Low JK, Khew Sk and Horace Tan