25 December 2021

Butterfly of the Month - December 2021

Butterfly of the Month - December 2021
The Yellow Flat (Mooreana trichoneura trichoneura)

A Yellow Flat sunbathing on a leaf with its wings spread open flat

And the final month of 2021 is here! It's the festive season, and the world needs to look ahead with more optimism. I am sure that we've had enough talk of COVID19 for the past 2 years, and it is something that everyone has grown tired of. Letting it continue to steal our precious time and control our lives will only make us more miserable. Despite a new variant and potentially more mutations, life has to go on. Measures are put in place, and risks are mitigated, and let us look forward to 2022 with greater optimism.


The month of December is a time for holidays, sharing time with our loved ones and a time for reflection and making resolutions for the new year ahead. In the northern hemisphere, the weather is generally colder and when birds fly south to warmer climes. But it is a time which gives meaning to a "White Christmas" and for us to revel in the beauty of Mother Nature's seasons.

A Yellow Flat feeding on pink Lantana flowers

Speaking of the weather, it is the monsoon season in Southeast Asia, and it has been particularly wet in neighbouring Malaysia. Inundated by floods over the past week, it is a grim reminder of climate change where extreme weather phenomenon affects many countries all around the world. The heavy rains continue unabated and it is likely that the floods will continue into the coming weeks. Strangely, the weather has been rather dry in Singapore with occasional thundery showers, but thus far, not enough to cause floods yet.


And over the past week or so, Singapore's news portals - both mainstream and social media have been filled with an uncommon "celebration" of sorts. News that a relatively unknown Singaporean badminton player - Loh Kean Yew, managed to upset higher ranked players, including World #1 Viktor Axelsen, on his way to win the BWF World Championship in Huelva, Spain. For the first time in its history, a Singaporean has won the BWF World Champion title - one that even neighbouring Malaysia (more of a badminton nation than Singapore) has never won before!

A Yellow Flat puddling on a concrete kerb

Our Butterfly of the Month for the final month of 2021 is the Yellow Flat (Mooreana trichoneura trichoneura). A newly discovered species for Singapore when it was spotted about nine years ago, the Yellow Flat is one of the species from the subfamily Pyrginae, often referred to as "Flats and Spread-Winged Skippers". It is described as a rare forest-dependent species in Malaysia, often flying in the lowlands.


Thus far, the species has only been spotted on the western side of Singapore, in the vicinity of the Nanyang Technological University (NTU). The Yellow Flat displays the typical behaviour of other species in the Pyrginae subfamily.  It is often observed perched on the tops of leaves to sunbathe or feeding on flowers. But when alarmed, it flies quickly under a leaf and perches with its wings opened flat.

The underside of the hindwing of the Yellow Flat is predominantly white

The upperside of the Yellow Flat's wings is dark brown with veins strongly dusted in white or pale yellow. The forewing bears a number of round and streaked hyaline spots in the distal half of the wing. The hindwing has a large yellow patch at the tornal area with yellow coloured cilia reaching up to vein 6. When viewed from the top, the abdomen is striped with pale yellow.


On the underside, the forewing is dark brown with the same set of spots as on the upperside. The hindwing is predominantly white from the dorsum to vein 6 with the white colouration diffusing into space 7 and beyond. Males of this species has a hair tuft on the mid- and hind tibiae.


The caterpillars have been successfully bred on a locally common plant, Mallotus paniculatus (Turn-In-the-Wind). This host plant is shared by several other local butterfly species. The caterpillar of the Yellow Flat creates a unique leaf shelter and makes it easy to spot when on the host plant. The adult butterfly, however, is not often seen in the field.


Wishing all our members and readers from around the world a Merry and Joyous Christmas and a Happy New Year!!

Text by Khew SK : Photos by Federick Ho, Huang CJ, Khew SK, Lim CA, Loh MY, Nelson Ong and Simon Sng

19 December 2021

Life History of the Julia Heliconian

Life History of the Julia Heliconian (Dryas iulia modesta)


Butterfly Biodata:
Genus: Dryasa Hübner, 1847
Species: iulia Fabricius, 1775
Sub-species: modesta
Wingspan of Adult Butterfly: 82-92mm
Caterpillar Local Host Plant: Passiflora suberosa (Passifloraceae, common name: corky-stemmed passion flower).






Physical Description of Adult Butterfly:
Julia Heliconian is a narrow-winged butterfly with elongated forewings. On the upperside, the wings are bright orange in the male and duller orange in the female. There are black borders along the wing margin, with those in the female broader and more extensive. On the underside, the wings for both sexes are paler compared to the upperside, and are adorned with brown markings in the cell, in post-discal area as well as along the wing margins. A small pinky red patch occurs in the basal area of both wings.




Field Observations of Butterfly Behaviour:
The Julia Heliconian is a recent addition to the Singapore butterfly checklist, with the first sighting reported in June this year. Similar to Tawny Coster, Julia Heliconian follows the same southward migration path from Thailand, through Malaysia and reaching Singapore in a few years. The first known local population is found in Lazarus and St. John islands where the adults can be sighted easily since August. Recently, the new emigrant has also been sighted with increasing frequency on the mainland. The adults are rapid in flight and not easy to photograph. Typically, photography opportunities arise when the butterflies visit flowers such as those of Lantana or Leea indica.




Early Stages:

A video clip showing the various early stages and key developments of a Julia Heliconian caterpillar.

Locally, caterpillars of the Julia Heliconian have been found to feed on leaves and stems of Passiflora suberosa. This plant is a fast growing weed and commonly found in many parts of Singapore in both urban and forest settings. It is also used as the larval host plant by the Tawny Coster.

Local host plant: Passiflora suberosa.

A mating pair of the Julia Heliconian.

Eggs of the Julia Heliconian are laid singly on a narrow stem or a tendril of the host plant. The stem or tendril where the egg is deposited on quite often is part of the dead portion of the passiflora vine.

A female Julia Heliconian ovipositing on a stem of its host plant, Passiflora suberosa, in Kuala Lumpur in 2015.

The yellowish egg is barrel-shaped and its surface is marked with small rectangular to hexagonal pits. The micropylar sits atop the egg. Each tiny egg has a diameter of about 0.9mm, and a height of about 1.2mm. After one day, the egg becomes mottled with reddish brown paches.

An egg of the Julia Heliconian laid on a dead stem of the host plant.

Maturing egg of the Julia Heliconian. Left: one day old; Right: three days old. The egg was laid on live stem of the host plant.

The egg takes about 3.5 days to hatch. The young caterpillar emerges by eating away part of the egg shell. The rest or part of the remaining egg shell becomes the first meal for the newly hatched which is about 2.4mm in length. It has a cylindrical and yellowish brown covered with many small tubercles and moderately long setae. The dorso-lateral and lateral bands of tubercles are indistinctly whitish. The head capsule is yellowish brown with no markings.

Two views of a newly hatched caterpillar of the Julia Heliconian, length: 2.4mm.

The 1st instar caterpillar feeds on the lamina of leaves. It has the habit of cutting a narrow strip from the leaf blade and rest on it between feeds. The body colour takes on a pale yellowish green undertone as it grows. The white tubercles because much more prominent as the the body grows. After reaching about 5-5.5mm in 2.5 days, the caterpillar moults to the 2nd instar.

Two views of a 1st instar caterpillar, length: 3.8mm.

Two views of a 1st instar caterpillar, length: 5.4mm.

A 1st instar caterpillar resting on a long strip of lamina cut from the side of a leaf.

A late 1st instar caterpillar, prior to its moult.

The body of the 2nd instar caterpillar is yellowish brown. Moderately long processes, black in colour, run along the length of the body. Each process has a number of short spines emanating from it laterally. On each side of the body, there are three series of such processes: One series occurs dorso-laterally, another lateraly and the last sub-spiracularly. Most of the tubercles at the base of these processess are whitish. There are also small white patches lying between these tubercles. The head capsule is yellowish brown with two short and black cephalic spines. The second instar caterpillar retains the same habit of cutting a strip of lamina and resting on it. This instar lasts about 2 days with the body length reaching about 8mm.

Two views of an early 2nd instar caterpillar, length: 6mm.

Two views of a 2nd instar caterpillar, length: 8mm.

A 2nd instar caterpillar resting on a long strip of lamina.

A late 2nd instar caterpillar, prior to its moult.

The 3rd instar caterpillar has the dorso-lateral, lateral processes and cephalic processes proportionately longer and black in color. The body base colour is dark yellowish brown and the white patches covering the body surface is more extensive than in the 2nd instar. The head capsule is still yellowish brown with the adfrontal area in a much paler shade of yellowish brown. This instar takes about 2 days to complete with body length reaching about 11-12mm. In the 3rd instar, the caterpillar swith from cutting a strip of leaf lamina to cutting the apical portion of a leaf.

An early 3rd instar caterpillar. Inset: another view of the head.

Two views of a 3rd instar caterpillar, length: 13mm.

A 3rd instar caterpillar resting on the cut-out fragment at the apex of a leaf.

A late 3rd instar caterpillar, prior to its moult.

The 4th instar caterpillar closely resembles the 3rd instar caterpillar. It has proportionately longer processes, and much more extensive and prominent whitish markings on the body as compared to those in the 3rd instar. In this instar, the caterpillar retains the habit of cutting the apical portion of the leaf. This penultimate instar lasts about 2 days with the body length reaching about 18-19mm.

A newly moulted 4th instar caterpillar. Inset: a frontal view of the head.

Two views of a 4th instar caterpillar, length: 18mm.

A 4th instar caterpillar resting on a leaf fragment cut from the apical part of the leaf.

A late 4th instar caterpillar, prior to its moult.

The 5th (and final) instar caterpillar differs from the 4th instar caterpillar in having the frontal side of the head black in colour, adfrontal area whitish and the rest (back of the head) yellowish to orangy brown. In addition, the body base collour is now pale pinky to purplish brown. The body surface is decorated with many small and transvese black patches/bands. Large and whitish patches line the lower side of the body.

A newly moulted 5th instar caterpillar of the Julia Heliconian.

A 5th instar caterpillar feeding on a stem of the host plant. Inset: front view of the head.

Two views of a 5th instar caterpillar, length: 34mm.

The 5th instar lasts for 3.5-4 days, and the body length reaches up to 34-35mm. On the last 0.5 day, the body shortens and the caterpillar ceases feeding and wanders around. Eventually it stops at a spot on the underside of a stem, and spins a silk pad from which it hangs vertically to take on the pre-J-shaped pupatory pose.

Two views of a pre-pupatory larva of the Julia Heliconian.

Pupation takes place about 10-11 hours later. The pupa suspends itself from the silk pad via the cremaster attachment. It is almost entirely white and bears a few small, black patches dorsally. The thorax is prominently keeled. Dorso-laterally, along the body length, there are pairs of short dorso-lateral processes. There are also pairs of silverish dorso-lateral patches on the first two abdominal segments. Length of pupae: 23-24mm.


The pupation event of a Julia Heliconian caterpillar .

Three views of a pupa of the Julia Heliconian. Left: lateral view. Middle: ventral view. Right: dorsal view.

Three views of a mature pupa of the Julia Heliconian.

After about 5-6 days of development, the pupal color darkens, especially so in the wing pads and thorax. The eclosion event takes place the next day, typically in the morning hours.


The eclosion event of a female Julia Heliconian.

A newly eclosed male Julia Heliconian resting on its pupal case.

A newly eclosed female Julia Heliconian resting on its pupal case.

The eclosion sequence of a Julia Heliconian.

References:
  • The Julia Heliconian's Samba Continues, Khew SK, ButterflyCircle Blog, May 2015.
  • Inferring the Provenance of an Alien Species with DNA Barcodes: The Neotropical Butterfly Dryas iulia in Thailand. Burg NA, Pradhan A, Gonzalez RM, Morban EZ, Zhen EW, et al. PLoS ONE 9(8): e104076. doi:10.1371/journal.pone.0104076, 2014.
  • Butterflies of Thailand, Pisuth Ek-Amnuay, 2nd Edition, 2012.
Text by Horace Tan, Photos by Tai Lung Aik, Gavin Gareth Chan, Loh Mei Yee, Khew SK and Horace Tan, Videos by Loh Mei Yee and Horace Tan.