02 April 2016

Butterfly of the Month - April 2016

Butterfly of the Month - April 2016
The Two Spotted Line Blue (Nacaduba biocellata)

All too soon, it's the fourth month of 2016 already! The weather in the northern hemisphere is rapidly warming up, as spring vegetation begins to emerge from the cold winter months. Over in Southeast Asia, temperatures appear to be warming up a tad faster than we would have preferred, with the mercury zooming past 38, 39 and 40ºC in Bangkok, Chiangmai, Penang, Kuala Lumpur and Singapore. In Japan, the Cherry Blossoms bloom heralding the start of the sakura or hanami time of the year.

Even in Singapore, visitors to the Flower Dome at the Gardens by the Bay queued up to partake in the visual treat of blooming Prunus sp. Cherry trees imported from various parts of the world. These trees were horticulturally "tricked" into flowering within the climate-controlled glass dome, creating Singapore's own sakura for visitors to enjoy.

Up north in Beijing, where I was attending a business conference, the weather was a crispy 13-16ºC in the daytime, dropping to a chilly 2-4ºC at night. Even so, the winds blew away the pollution and the air was clean and clear. The hotel where we had the conference at was about 100km away from the city centre, and the surrounding views were spectacular! Magnolia buds have started appearing on their leafless trees, all ready to bloom as springtime temperatures trigger renewed life, as it does year after year.

On the global front, the spectre of religious extremism and radicalisation continues with terrorist acts claiming innocent lives of women and children. Two recent suicide bombings in Brussels, Belgium and Lahore, Pakistan claimed the lives of over 100 people. Other than these high profile cases which are featured internationally, it is terrifying when one is informed about the number of less well-known terrorist attacks all over the world, all in the first 3 months of 2016 alone!

The construction industry in India was thrust into the limelight when a massive flyover collapsed in Kolkata (formerly Calcutta) and killed more than two dozen people. The purported lack of inspections and quality of material used by the "blackmarked" contractor was cited as possible causes. This led me to think about how we architects and engineers often lament about the highly regulated construction industry in Singapore where the Building and Construction Authority (BCA) and many other agencies tend to "over-regulate". Perhaps we have to be thankful for that after all!

Workplace safety was in the limelight in Singapore, where two engineering technicians were killed when they were knocked down by a moving train whilst en route to check a track fault. This brings into question, the level of workplace safety procedures in such hazardous industries. In the engineering and construction industry, where foreign workers make up a higher proportion of the workforce, workplace health and safety is always a concern where 'one life lost is one life too many'.

Speaking of foreigners and immigrants, we feature a non-local butterfly species that was discovered some time back in 2004 - the Two Spotted Line Blue (Nacaduba biocellata). This immigrant species is a diminutive 16-22mm in wingspan and is unlikely to have made it all the way from Australia, its native home, to Singapore. The fact that its caterpillar host plants are also non-native invasives - the Black Wattle (Acacia auriculiformis) and the Silver Wattle (Acacia mangium) makes it curious as to how these "foreigners" got to Singapore.

Both the host plants are considered invasive "weeds" and often removed by parks managers due to their brittle trunks and branches and are susceptible to breaking and collapsing. Surely they could not have been imported by horticultural companies where the caterpillars and pupae of the butterfly may have stowed away on? If so, then how did the butterflies appear in Singapore?

The male Two Spotted Line Blue is lilac with dark blue basal area while the female is dull brown with varying degrees of blue in the basal area. Both sexes have two brown-black subtornal spots on the hindwing. Underside, both sexes are similarly marked. The underside is pale greyish-orange in base colour with a short band at cell-end, and a longer post-discal band, both of which are narrowly edged with brown and white. The hindwing features two black subtornal spots with a few iridescent green scales and ringed with pale yellow-brown.

The species is skittish and often flies erratically for long periods of time without resting. An interesting phenomenon about the Two Spotted Line Blue is that its appearance in Singapore is highly seasonal. It suddenly appears as a outbreak, where literally hundreds of individuals may be observed over a few days, fluttering around the vicinity of its host plant. And then it disappears for the rest of the year, with not a single individual seen until the next outbreak!

It is often mistaken for the more commonly found Tailless Line Blue (Prosotas dubiosa lumpura) which displays a similar behaviour and outbreak over the year. Until an individual stops to rest and shows its distinctive two tornal spots, the two different species are usually difficult to distinguish when it flight.

Sightings of the Two Spotted Line Blue have been quite regular over the years so as to conclude that this species has somehow been naturalised and considered a "permanent resident" in Singapore. Its caterpillar host plants, as mentioned earlier, grows easily and appears in undeveloped areas all over Singapore. The full life history has been documented and can be found on this blog here.

It is hoped that this species will continue to survive in Singapore, despite the mystery of how it immigrated to Singapore. Being seasonally common, it is also a mystery of nature how its caterpillars or pupa is able to 'hibernate' and appear again the next season. This species has not been recorded in Malaysia yet, and should be looked out for in Singapore's neighbouring state of Johor.

Text by Khew SK : Photos by James Chia, Sunny Chir, Khew SK, Koh CH, Horace Tan and Anthony Wong

Cross References on this Blog :