Butterfly of the Month - June 2023

Butterfly of the Month - June 2023

The Darky PlushBlue (Flos anniella anniella)

Half of the year 2023 is almost over, as we wind down towards the last days of June. Did you manage to achieve what you targeted to do? As far as resolutions go, what have you ticked off your to-do list for the year? Not to worry, there are six more months to go! The month of June belongs to the astrological sign Gemini. For those born between 21 May and 21 June, your zodiac sign is Gemini. We featured Capricorn, Aquarius, Pisces, Aries and Taurus in the preceding Butterfly of the Month blogposts and will now move into the next in the series. The 12 zodiac signs are Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.

Gemini (♊︎) (/ˈdʒɛmɪnaɪ/ JEM-in-eye, Greek: Δίδυμοι, romanized: Dídymoi, Latin for "twins") is the third astrological sign in the zodiac. Under the tropical zodiac, the sun transits this sign between about 21 May to 21 June. Gemini is represented by the twins, Castor and Pollux, known as the Dioscuri in Greek mythology. Gemini is represented by a set of twins (or in Egyptian astrology by a pair of goats and in Arabian astrology by a pair of peacocks).

Those born under this zodiac sign are very versatile and multifaceted. They do not miss the opportunity to comprehend everything and, if possible, even more. Playful and intellectually curious, Gemini is constantly juggling a variety of passions, hobbies, careers, and friend groups. They are the social butterflies of the zodiac. Despite their unfair reputation for being two-faced, once a Gemini is in your life, they're loyal for life — but they aren't afraid to voice their opinion if they feel you're doing something they disagree with or if they perceive you as not being loyal to them.

Gemini can sometimes be very inconsistent and can change their attitude, opinions, and affairs several times a day. They often do not "close the loop" as they are engaged in several things at once, and jumping from one thing to another. This perpetual motion machine needs frequent changes in their social circle. He usually knows a lot of people, but they often don’t have a "best friend forever" type of friends. Most often, representatives of this sign become lawyers, journalists, public figures, or choose creative professions – designers, artists, poets, etc.

Our feature butterfly for the month of June 2023 is the Darky Plushblue (Flos anniella anniella). This species is often considered the rarest of the four (now five, with the addition of Flos abseus abseus after a recent taxonomic reclassification) Flos species in Singapore. Its preferred habitat is the heavily-shaded forest understorey in Singapore's nature reserves and nature parks. It can sometimes be spotted feeding at flowering trees at the forest edges.

A female Darky Plushblue opens her wings to sunbathe

The upperside of the Darky Plushblue is a lustrous violet-blue with a thin black border in the males, but with broad black border in the females. The underside is mostly dark purple blue with cryptic markings and white streaks typical of the other species in this genus. The apical area of the underside of the forewing is whitened.

A male Darky Plushblue perches on a twig showing a glimpse of its lustrous purple-blue upperside

The Darky Plushblue is tailless, although the hindwing is slightly toothed at veins 2 and 3. It also lacks the red patch at the base of the underside of the fore- and hindwings unlike some of its relatives in the genus. The tornal spots on the underside of the hindwing are smaller than the other Flos species and the iridescent blue/green scaling is very much reduced.

The Darky Plushblue is skittish and a strong flyer. They typically perch with their wings closed in heavily shaded habitats. But in sunny weather the females have been observed to open their wings fully to sunbathe in between ovipositing runs. Individual adults have also been seen visiting flowers and ripened fruits of the Singapore Rhodendron (Melastoma malabathricum).

Text by Khew SK : Photos by Federick Ho, Khew SK, Loke PF, Jonathan Soong, Horace Tan and Benjamin Yam.

Life History of the Cowan's Flash

Life History of the Cowan's Flash (Rapala cowani)

Butterfly Biodata:
Genus: Rapala Moore, 1881
Species: cowani Corbet, 1939
Wingspan of Adult Butterfly: 31-33mm
Caterpillar Local Host Plant: Xylocarpus granatum (Meliaceae, common names: Mangrove Cannonball Tree, Nyireh Bunga, 木果楝).

A female Cowan's Flash.

A male Cowan's Flash.

A male Cowan's Flash.

Physical Description of Adult Butterfly:
On the underside, the markings on both forewing and hindwing are common in most Rapala spp., featuring a cell-end bar, a black post-discal band and indistinct submarginal fascia. The male is pale greyish brown while the female is pale greyish. On the hindwing, an orange-crowned black marginal spot is present in space 2 and on the tornal lobe. Between the two spots, the marginal area in space 1b is covered with pale bluish silvery scales. There is a white-tipped black tail at the end of vein 2. On the upperside, the male is bright orange-red with very broad dark brown borders on both wings, and the female is yellowish brown with brown border on the forewing. As with other Rapala spp., the male has in its hindwing a prominent oval-shaped brand at the base of space 7, and a secondary brand at the base of vein 6.

A female Cowan's Flash.

Upperside view of a female Cowan's Flash.

A male Cowan's Flash.

Field Observations:
The Cowan's Flash is rare in Singapore. Since its discovery in 1938 at the mouth of Sungei Jurong, no sightings have been reported for several decades in the mainland. Its recent sightings are confined to mangrove areas in Pulau Ubin and Sungei Buloh Wetland Reserve, in the vicinity of its larval host plant. The adults are fast flyers and take rapid flights among foliage at the water edge.

A recent sighting of a male Cowan's Flash at the Sungei Buloh Wetland Reserve.

Another recent sighting of a female Cowan's Flash at the Sungei Buloh Wetland Reserve.

Another Cowan's Flash sighted recently at the Sungei Buloh Wetland Reserve.

Early Stages:
Thus far, only one local larval host plant, namely, Xylocarpus granatum, a mangrove plant, has been confirmed. The caterpillar of the Cowan's Flash has also been found feeding on leaves of another mangrove plant, Allophylus cobbe, but did not survive till the adult stage. Hence further observations are required for the confirmation of this second plant.

On the host plant, caterpillars of the Cowan's Fash feed on young leaves and young stems. In the 1st to the 4th instar, the caterpillar feeds by grazing the leaf surface. At times in the 4th instar and in the entire 5th intar, the caterpillar switches to feeding along the leaf edge. In their natural habitats, the caterpillars are typically found in the company of a species of small black ants in a symbiotic relationship.

Local host plant: Xylocarpus granatum.

Young leaves of Xylocarpus granatum.

The eggs are laid singly on the surface of a stem of the host plant, usually on or near a node. Each egg is about 0.8mm in diameter, 0.5mm in thickness and green in colour. It is burger-shaped with a depressed micropylar at the pole. The egg surface is covered in a finely reticulated pattern.

A female Cowan's Flash attempting to oviposit on a leaf of the host plant.

Two eggs of the Cowan's Flash laid near the node of a stem of the host plant.

Two close-up views of an egg of the Cowan's Flash.

It takes about 3 days for the egg to hatch. The newly hatched is pale yellowish with moderately long dorsal and lateral setae. Its body has a length of about 1.6mm. Reddish brown patches can be seen on the 1st, 6th-8th abdominal segments and on the anal plate. It also has a black prothoracic shield and a black head. After about 2 days of growth in the first instar, and reaching a length of about 2.6mm, the caterpillar moults to the next instar.

Two views of a fully developed egg of the Cowan's Flash.

1st instar caterpillar, newly hatched, length: 1.1mm.

Two views of a 1st instar caterpillar, length: 2.6mm.

A 1st instar caterpillar begin tended by an ant.

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

The 2nd instar caterpillar has dark reddish brown patches on the thoracic segments, as well as in the 1st, 6th-8th abdominal segments. There are also two brown spots on the anal plate. From above, the 7th to 10th segments appear to have fused together to form a saucer-like structure. The dorsal nectary organ on the 7th abdominal segment is now discernible. There are short black setae emanating from rows of conical projections occurring dorso-laterally. Numerous pale yellowish short setae occur sub-spiracularly along the body fringe. The 2nd instar caterpillar reaches a length of about 4.2mm, and after about 2 days in this stage, it moults again.

Two views of a newly moulted 2nd instar caterpillar.

Two views of a 2nd instar caterpillar, length: 3.6mm.

A 2nd instar caterpillar being tended by ants.

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

The 3rd instar catepillar resembles the 2nd instar caterpillar closely, but with the hair-like setae replaced by paddle-like setae. These paddle-like setae are brown to black for those occuring dorso-laterally and on the posterior segments, while remaining ones along the body fringe are pale yellowish brown. On the 7th abdominal segment, the dorsal nectary organ is now more readily observed. The 3rd instar takes about 3 days to complete with the body length reaching about 8.5-9mm before the next moult.

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

Two views of a 3rd instar caterpillar, length: 8mm.

A 3rd instar caterpillar feeding on a young leaf while being tended by ants.

Two views of a late 3rd instar caterpillar, dormant prior to its moult, length: 8mm.

The 4th instar caterpillar has a more strking appearance, featuring broad triangular to semi-circular yellowish green or pale yellowish brown dorsal markings on the 2nd to 5th abdominal segement, and brown to dark brown lateral patches on almost all body segments. All body setae, whether occuring dorso-laterally or along body fringe are now much shorter in proportion to the size of the body segments. Tentacular organs on the 8th abdominal segments can now be easily observed being everted from time to time. The 4th instar takes about 3 days to complete with the body length reaching 13.8 to 14mm.

Two views of a Cowan's Flash caterpillar, in th midst of moulting to the 4th instar.

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

A 3rd instar and a 4th instar caterpillar of the Cowan's Flash, with ants in attendance.

Two views of a late 4th instar caterpillar, dormant prior to its moult.

The 5th and final instar caterpillar is much larger with increases in both body length and width. It has similar markings as in the previous instar. In this instar, the caterpillar mostly feeding along the leaf edge.

Two views of a 5th instar caterpillar, newly moulted.

An early 5th instar caterpillar with yellowish green dorsal markings, feeding on the leaf edge, length: 15.5mm.

Two views of an early 5th instar caterpillar with yellowish brown dorsal markings, length: 14.5mm. Note the everted tentacular organs on the 8th abdominal segment.

Two view of a late 5th instar caterpillar, length: 21mm.

After about 3 to 4 days of feeding and reaching a length of about 22mm, the caterpillar stops food intake and wanders around for a pupation site. During this time, its body gradually shortened and body color darkens. Typically the caterpillar chooses a concealed space in a leaf litter for its pupation site.

Two views of a late 5th instar caterpillar with a darkened appearance. An ant can be seen tending to it.

The pre-pupatory caterpillar prepares for pupation by spinning a silk girdle and a silk pad to which it attaches itself via anal claspers. After about 1 day as a pre-pupa, pupation takes place. The pupa has a shape typical of most lycaenid species with a length of 13.8-14.2mm. It is pale reddish to yellowish brown in base colour, and its surface bears numerous small dark speckles.

Two views of a pre-pupa of the Cowan's Flash.

Two views of a fresh pupa of the Cowan's Flash, moments after the pupation event.

Two views of a pupa of the Cowan's Flash.

Eight to nine days later, the pupa darkens, first in the wing pad and thorax, then progressively in the abdomen. The presence and absence of the reddish patch in the wing pads gives an early indication of the sex of the soon-to-emerge adult. The next day, the pupal stage comes to an end with the emergence of the adult butterfly.

Two views of a mature pupa of the Cowan's Flash.


Video: A female Cowan's Flash emerging from its pupal case.


Video: A male Cowan's Flash emerging from its pupal case.

A newly eclosed male Cowan's Flash resting on its pupal case.

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.
• Biodiversity Record: Rediscovery of the butterfly, Rapala cowani, on Singapore Island, Loh J, Low JK & Soh ZS-H, Nature in Singapore, 15: e2022113. DOI: 10.26107/NIS-2022-0113, 2022.

Acknowledgment:
I would like to express my gratitude to Lim Cheng Ai and Sebastian Ow for sharing sighting information of an ovipositing Cowan's Flash and identification of the larval host plant.

Text by Horace Tan, Photos by Sebastian Ow, Lim Cheng Ai, Low Jian Kai, Loh Mei Yee, Khew SK and Horace Tan, Videos by Loh Mei Yee and Horace Tan.