Life History of the Horsfield's Baron

Life History of the Horsfield's Baron (Tanaecia iapis puseda)

Butterfly Biodata:
Genus: Tanaecia Butler, 1869
Species: iapis Godart, 1824
Subspecies: puseda Moore, 1858
Wingspan of Adult Butterfly: 65mm
Caterpillar Host Plants: Melastoma malabathricum (Melastomataceae).


A female Horsfield's Baron giving us a view of its upperside.


A male Horsfield's Baron displaying its wing upperside.

Physical Description of Adult Butterfly:

T. iapis puseda exhibits sexual dimorphism. Above, the male is dark velvety black with its hindwing hosting a broad greenish-blue distal border which is continued narrowly along the termen of the forewing. The larger female is pale ochreous brown, and has a post-discal series of helmet-shaped white spots and a less distinct marginal series of spotts on both fore- and hindwings. Underneath, the male is pale ochreous brown with a series of dark striae in the forewing cell, but without any white spots. The female has additional marginal and post-discal series of whitish spots on both fore- and hindwings.

A puddling male Horsfield's Baron.


A male Horsfield's Baron perching with a closed-wing posture.
Field Observations of Butterfly Behaviour:

The Horsfield's Baron is relatively common in Singapore. They are mainly found in the nature reserves, but at times adults can be seen flying in public parks and wastelands where the host plants are growing in abundance. Both sexes have the habit of resting on perches with wings open. The male exhibits territorial behaviour of chasing intruders in the vicinity of its perch. On rare occasions, the male have been observed to puddle on damp ground. Refer to this earlier butterfly-of-the-month article for a more detailed write-up on this species.

Early Stages:

The host plant, Melastoma malabathricum, is a widespread weed in Singapore. An earlier blog article has a detailed write-up of its characteristics and its relationship with other local butterfly species. Caterpillars of Horsfield's Baron feed on the middle-aged to mature leaves of this amazing plant.

Host plant : Melastoma malabathricum. Leaves, flower buds and flowers are shown.


A mating pair of the Horsfield's Baron.


A mother Horsfield's Baron laying an egg at a leaf tip of the host plant.

The eggs are laid singly at the leaf tip of the host plant. Each egg has a tall dome shape with a base diameter of about 1.8mm. The surface is covered with large hexagonal depressions with hair-like protuberances emerging from adjoining corners. When freshly laid, the surface is moist and in pale green. Within hours, the moisture evaporates and the color turns to a darker shade of green.

Two views of an egg of the Horsfield's Baron.


Two views of a near-mature egg of the Horsfield's Baron, one day prior to hatching.

After about 4.5-5 days, the 1st instar caterpillar emerges and proceeds to eat the eggshell as its first meal. The caterpillar is yellowish green in body colour and has a pale yellowish brown head capsule adorned with two brownish lateral stripes. Its body sports ten pairs of long and "fleshy" dorso-lateral protuberances. Black setae emanate from the body below these long protuberances and from a series of short dorsal protuberances. Frass pellets are usually seen attached to the tip of these setae in this instar. The caterpillar grows from an initial length of about 4mm to 6mm in 1.5-2 days. The subsequent moult takes it to the 2nd instar.

Two views of a newly hatched 1st instar caterpillar. Top: taking a pause after emergence; Bottom: nearly done with eating its own egg shell.
Two views of a 1st instar caterpillar, early in this stage, length: 4mm.

1st instar caterpillar, late in this stage, dormant prior to the moult, length: 5.5mm

The body of the 2nd instar caterpillar is predominantly yellowish green. All ten pairs of short protuberances seen in the 1st instar have lengthened considerably. Each is projected horizontally with numerous branched spines and is almost always pressed to the leaf surface. The protuberance is mainly pale yellowish in color with some spines colored black in the middle and the tip portion. On the dorsum, pairs of white patches appear between the 3rd to the 10th protuberances. As growth progresses in this instar, each pair of white patches become conjoined to appear as an eye-shaped patch. The 2nd instar lasts for 3-4 days with the body length reaching about 9.5-10mm before the moult to the 3rd instar. Note that the length given here and for later instars is measured between the head and the posterior end of the last body segment, excluding the length of protuberances projected head and behind the body segments.

Two views of 2nd instar caterpillar, early in this stage, length: 8mm

A 2nd instar caterpillar, length: 8.5mm


A 2nd instar caterpillar, late in this stage, dormant prior to its moult, length: 8mm.

The 3rd instar caterpillar is still greenish in body color. There are a few small spots on the body. The protuberances have all become much longer in proportion. The branched spines appear almost like a bird's feather, with the secondary spines arranged neatly around the main spine. Dorsally the series of eight white-oultined patches become more prominent, and toward the later part of this instar, the central portion of each patch becomes darkened. The 3rd instar lasts for 3.5-4 days and reaches a length of about 15-16mm before the next moult. Towards the end of this instar, the body color gradually changes to jade green.

A newly moulted 3rd instar caterpillar. Note the exuvia lying nearby.

Two views of a 3rd instar caterpillar, length: 11mm.

3rd instar caterpillar, late in this stage, length: 15mm

The 4th instar caterpillar has similar appearance as in the 3rd instar but with a pale yellowish green body color. Horizontal spines on each long protuberance are mostly pale green while shorter vertical spines are black in color. The distal portion of the protuberance is mostly colored white. The dorsal marks becomes more shield-like in appearance with the central portion taken up by a large purplish/pinkish patch encircling a small dark bluish spot. After 5-6 days in this instar, with its length reaching 22-24mm, the caterpillar moults to the 5th and final instar.

A 4th instar caterpillar which has just shed its old skin.


Dorsal view of a 4th instar caterpillar, length: 22mm.


Another view of the 4th instar caterpillar.

Essentially similar to the 4th instar caterpillar, the 5th instar features a darker shade of jade green. The number of small white spots on the body has increased. The dorsal shield-like spots are also larger and more prominent visually.

5th instar caterpillar, early in this stage, length: 25mm.


5th instar caterpillar, first 2 dorsal spots.
5th instar caterpillar, last 3 dorsal markings.
5th instar caterpillar, late in this stage, length: 35mm.

This final instar lasts for 7-9 days with the caterpillar reaching a mature length of about 35-38mm. On the last day, the caterpillar ceases its feeding activity and its body becomes shortened. It then seeks out a spot on the underside of a mature leaf and stays put. There it laboriously spins large quantity of silk threads to make a silk mound, to which its posterior claspers are then attached to. Now the pre-pupa hangs from this anchor point in a head-down posture. By this time, each dorsal shield-like markings has decolorized to become just a ring of white surrounding a central green to dark blue patch. A short transverse white band appears on the dorsum about mid-body. Nearing the end of the pre-pupal phase, all traces of dorsal markings are nearly gone except for the very first one which becomes a yellow spot. The short transverse band turns yellow by this time too.

Two views of a pre-pupa of the Horsfield's Baron. Left: early pre-pupa; Right: late pre-pupa.

After 0.75-1 day of the pre-pupal stage, pupation takes place. The pupa is suspended with its cremaster firmly attached to the silk mound. It has a smooth body which tapers steeply towards each end from a high transverse dorsal ridge which is lined with an interrupted golden transverse band. The green pupa has a series of golden-colored spots symmetrically arranged. Two short golden-colored cephalic horns are also featured. Length of pupae: 18-20mm.

The pupation event of a Horsfield's Baron caterpillar.

Two views of a newly formed pupa of the Horsfield's Baron.

Two views of a pupa of the Horsfield's Baron.

Nine days later, the pupa becomes considerably darkened, especially in the wing case area, signaling the end of the development of the adult still encased within. The next day, the adult butterfly ecloses and stays near the empty pupal case for an hour or two before taking its first flight.

Two views of a mature pupa of the Horsfield's Baron.

A newly eclosed male Horsfield's Baron clinging on its empty pupal case.

A newly eclosed male Horsfield's Baron.

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, 1st Edition, 2006

Text by Horace Tan, Photos by James Chia, Ellen Tan, Sunny Chir, Khew SK and Horace Tan

Observation Notes on the Variability of the Baron

Observation Notes on the Variability of the Baron


A typical male Baron sunbathes with its wings opened flat

The Baron (Euthalia aconthea gurda) is a relatively common butterfly in Singapore. It can be found in urban areas, as well as in forested areas and even at coastal parks. The preferred caterpillar host plant, the Mango (Mangifera indica) is cultivated in home gardens, as roadside trees, and can even be found at abandoned fruit orchards and nurseries at the fringes of our nature reserves.

An underside shot of a male Baron. Note the five distinct postdiscal spots on the forewing

The species is quite widespread but is usually found close to the vicinity of its host plant (of which there are probably more than one host plant besides Mango). The butterfly is robust and skittish and has a powerful flight where it flaps and glides quickly amongst the foliage in parks and gardens.

A typical female Baron with five distinct post-discal spots on the forewing

The wings of both sexes are dark brown with a broad but rather obscure post-discal band on both wings, the inner edge of this band is defined by a few white spots on the forewing. The female is paler in appearance and the post-discal white spots are larger than in the male. The underside is a paler brown with space 7 of the forewing whitened.

Another female Baron with the typical five post-discal spots on the forewing with those in spaces 2 and 3 are smaller and moved out of line with those in spaces 4-6.

The post-discal spots in spaces 2 & 3 of the forewing are moved inwards out of line with the spots in spaces 4-6. In the female the spots in spaces 2 & 3 are generally much smaller than in spaces 4-6.

One of the variants of the female Baron, where the post-discal spots in spaces 2 and 3 are missing. On the upperside of this individual the spots in spaces 4-6 are sullied and almost obscure

Over the years, ButterflyCircle members have taken shots of the species in various locations where the characteristic white post-discal spots are either missing or of varying sizes. In the identification of butterflies, where even a single spot can suggest a totally different species this wide variability in the Baron, particularly in the females, is most intriguing.

The first variant displays only three post-discal spots in spaces 4-6 with the spots in spaces 2 & 3 totally missing. This is consistent on both the upperside and underside of the butterfly. Whilst the males display more consistency in the post-discal spots, the females have shown a whole range of permutations in the presence (or absence) of the post-discal spots. These variations appear to even suggest a totally different species!

The variant shown above displays the typical five spot arrangement, but with the spots in spaces 2 & 3 almost in line with the other three spots in spaces 4-6.

Another example of a female Baron shown above where the spots in spaces 2 & 3 are missing, but the spots in spaces 4-6 are small and indistinct.

A rather unique individual of the female Baron where the post-discal spot in space 3 is very small and almost obscure, whilst there is an additional spot in space 1b of the forewing! Also note that the spot in space 2 is larger than those in spaces 4-6.

Whilst the differences in the post-discal spots in the female Baron suggests that the species is highly variable in these physical characteristics, further field observations have indicated that they are not of a different species.

Text by Khew SK : Photos by Goh LC, Khew SK, Anthony Wong & Mark Wong

Life History of the Common Imperial

Life History of the Common Imperial (Cheritra freja frigga)

Butterfly Biodata:
Genus: Cheritra Moore, 1881
Species: freja Fabricius, 1793
Sub-species: frigga Fruhstorfer, 1912
Wingspan of Adult Butterfly: 30-42mm
Caterpillar Local Host Plants: Adenanthera pavonina (Leguminosae, common name: Red Saga), Callerya atropurpurea (Leguminosae), Cinnamomum iners (Lauraceae, common name: Wild Cinnamon), Duabanga grandiflora (Lythraceae)






A male Common Imperial displaying its upperside

Physical Description of Adult Butterfly:

Above, the male is purplish brown and the female is dark brown. Both sexes have large quadrate tornal spots in spaces 1b and 2 of the hindwing. These spots are outlined in white, more broadly so in the female than in the male. Underneath, both sexes are mostly white and have orange brown shadings on nearly the entire forewing and just the apical area of the hindwing. There is a narrow, indistinct ochreous brown post-discal line on the forewing. On the hindwing, the post-discal line occurs in short stripes and becomes darker and bolder towards the lower half of the wing. In addition, there is an interrupted dark submarginal line, a series of tornal spots on the tornal lobe and spaces 1b, 2 and 3. Metallic bluish green scalings overlay these spots. A long filamentous tail, up to 25mm, occurs at the end of vein 2. In contrast, a much shorter tail occurs at the end of vein 1b.

Field Observations of Butterfly Behaviour:

The Common Imperial is moderately rare in Singapore. The adults are more commonly sighted in the Southern Ridges, in addition to sporadic sightings in the nature reserves and other urban parks and gardens. It frequents forested areas and flies in a similar manner as its more common relative, the Branded Imperial. As the adult butterfly flies from one perch to the next, the long tails trails elegantly behind the butterfly.

Early Stages:

The immature stages of Common Imperial are polyphagous. To date 4 plants have been recorded as its local hosts. Caterpillars of all instars feed on young and tender leaves of the host plants. They are also polychromatic, occurring mainly in either a green form or a pink form.

Local host plant #1: Duabanga grandiflora.


Local host plant #2: Adenanthera pavonina


Local host plant #3: Cinnamomum iners

A mating pair of the Common Imperial.

A mother Common Imperial laying an egg on a young leaf of the Wild Cinnamon.

Eggs are laid on the underside of a young leaf or other parts of a young shoot of the host plant. The white egg, about 0.9mm in diameter, is shaped like a slightly flattened chinese bun. The surface is covered with numerous pits of varying sizes. The polar pit holds the depressed micropylar.


Two views of an egg of the Common Imperial. Diameter: 0.9mm.

A Common Imperial caterpillar emerges from its egg shell.

Each egg takes about 2 to 2.5 days to hatch. The young caterpillar emerges after nibbling away sufficiently large upper portion of the egg shell. Measured at a length of about 1.1-1.2mm, its pale yellow green body is roughly cylindrical in shape. Dark and long setae run dorso-laterally and whitish long setae run laterally. Its head capsule is pale yellowish, and both its prothoracic shield and anal plate are colored as per the body base colour.

Two views of a newly hatched caterpillar of the Common Imperial, length: 1.2mm

As the caterpillar grows, raised tubercles become apparent on the dorsum, one pair to each of 2nd-3rd thoracic segments, and one to each 1st-7th abdominal segments. Body color is whitish alongside this row of tubercles, forming two white bands visually. Another two yellowish green bands line the outer sides of these white bands. This instar lasts for 2.5 to 3 days with the body length reaching up to 2.7mm.

Two views of a 1st instar caterpillar, length: 2mm.

Covered with numerous short setae, the body of the 2nd instar caterpillar is either whitish with a yellowish green tone or pinky tone. Each of the 2nd and 3rd thoracic segments has a pair of dorso-lateral conical projections, whilst each of the first six abdominal segments have a tall conical projections, taller than those on the thoracic segments. These projections are yellowish brown around the tip and whitish at the base. The 7th abdominal segment is broadened laterally compared to the other segments. In addition to the dorso-lateral white bands, a lateral white band also become discernible along the rim of the body. The growth in this stage brings the caterpillar to a length of about 5mm, and after about 2 days in this stage, it moults again.

Two views of a 2nd instar caterpillar, lengths: 4mm.


Two views of a 2nd instar caterpillar, late in this stage, length: 4.9mm.

The 3rd instar caterpillar resembles the 2nd instar caterpillar closely with minor changes observed. The dorsal projections on the abdominal segments are now much longer and pointed than those on the thoracic segments. The lateral projections on the 7th thoracic segments are also much more pronounced than in the earlier instar. both the prothoracic shield and the anal plate are black and well developed. This instar takes 2.5-3 days to complete with the body length reaching about 10.5mm before the next moult.

Two views of a 3rd instar caterpillar, length: 5mm.


Two views of a 3rd instar caterpillar, late in this stage, length: 10.5mm.

The 4th instar caterpillar bears a few changes from the 3rd instar. One visual difference is the missing white bands flanking the dorsal projections on the abdominal segment. The body base color is either green (green form) or pink (pink form). The dorso-lateral pairs of projections seen on the 2nd-3rd thoracic segments in earlier instars are no longer discernible. Furthermore, yellowish brown to dark brown patches occur laterally in 3rd-5th abdominal segments, increasing in size from the 3rd to the 5th segment. This instar lasts about 3-4 days with length reaching 20-22mm.

Two views of a 4th instar caterpillar, length: 14.5mm.

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


Two views of a 4th instar caterpillar, green form, late in this stage.

Towards the end of the 4th instar, the caterpillar ceases eating and chooses a spot on an inclined leaf surface or a stem for its pupation site. At this time, the caterpillar's body shrinks in length and its body changes to a shade of green color (even for the pink form). The lateral patches surrounding the dorsal projections also decolorise drastically. It spins a silk pad and then anchors itself on it in a head-down posture.

Two views of a pre-pupatory larva of the Common Imperial.

Pupation takes place after one day of the pre-pupal stage. The pupa has the typical lycaenid shape, yellowish green in base colour with pale yellowish brown markings on the first 6 abdominal segments. The wing case and the dorsum of the thorax is greyish brown to greenish brown. Length of the pupa: 10-12mm.

Two views of a pupa of the Common Imperial.

5.5-6 days later, the mature pupa turns dark in the dorsal and wing case areas, and yellowish brown elsewhere. The next day the adult butterfly emerges from the pupa.

Two views of a mature pupa of the Common Imperial.

A newly eclosed Common Imperial resting near its pupal case.

References:

• [C&P4] The Butterflies of The Malay Peninsula, A.S. Corbet and H.M. Pendlebury, 4th Edition, The Malayan Nature Society.
• Butterflies of Thailand, Pisuth EK-Amnuay, 1st Edition, 2006.

Text by Horace Tan, Photos by Anthony Wong, Federick Ho, Sunny Chir, Khew Sin Khoon and Horace Tan