29 September 2012

Butterfly of the Month - September 2012

Butterfly of the Month - September 2012
The Acacia Blue (Surendra vivarna amisena)

The month of September blows past, bringing in the colder winds of autumn in the northern hemisphere as the year 2012 move towards its final three months. As the 9-11 (Sep 11) anniversary came and went without much incidents, the month of September 2012 featured unrest again in the Islamic world, as Muslims protested rather violently against an ill-conceived film produced by an amateurish zealot in the US who definitely wasn't using his brain (if he had one).

Elsewhere nearer in Asia, disputes erupted between China and Japan over a few little uninhabited rocks in the sea - the Senkaku Islands (to the Japanese, or Diaoyu Islands, to the Chinese). The Senkaku Islands are located in the East China Sea between Japan, the People's Republic of China, and Taiwan. The archipelago contains five uninhabited islands and three barren rocks, ranging in size from 800m2 to 4.32km2.

In various cities in China, protesters damaged Japanese-owned establishments and objects of Japanese origin.  Again, a senseless display of violence and destructive nature of human beings, stirred up by nationalistic fervour and challenge to a nation's sovereignity.  One can only hope that diplomacy and common sense will prevail to end such unrest, in a turbulent world that is already unstable in the face of economic crisis.

Back in Singapore, concerns of a recession looms, as indicators show some evidence of a softening economy across many sectors.  Will Singapore be able to take another storm so quickly?  Or will it be another short-lived downturn that will pass quickly? On another pressing issue, that sparked active national "conversations" it has been estimated that Singapore's population has increased to 5.31 million, and growing. That's 7,257 persons per sq km! From the Department of Statistics' site, only 61.8% of the population are Singapore citizens, with the other 38.2% non-citizens. What should Singapore's 714 sq km carrying capacity be? The jury is still out on that.

September's Flower is usually associated with the Aster. There are roughly 180 species within the genus, all but one being confined to Eurasia. The name Aster comes from the Ancient Greek word ἀστήρ (astér), meaning "star", referring to the shape of the flower head. The Aster is unique for its delicate purple colour.  Legend has it that burning the Aster leaves will keep away snakes. In French tradition it is said that placing the flowers on the grave of a dead soldier is a tribute to his bravery.

Our feature butterfly for September is the Acacia Blue (Surendra vivarna amisena).  This small Lycaenid (wingspan about 28-32mm) is not rare. It is more often encountered in the forested areas than urban Singapore, although it is quite widespread in distribution, and occurs in parks and gardens as well.  It has a rapid flight and can be quite skittish.  Females are often encountered in the vicinity of its favourite host plant, the Albizia.  

The English common name "Acacia" suggests that the butterfly has some sort of association with the Wattles (Acacia spp.).  Indeed, upon checking up on the genus Surendra, there are related species like S. quercetorum (a species that does not occur in Singapore) does feed on species of Acacia like Acacia pennata. This could have been the rationale for the origin of the name Acacia Blue, although here in Singapore, the species has thus far not been known to be associated with any Acacia plants.

Sunbathing Acacia Blues showing off their uppersides - top female; bottom male

The male Acacia Blue is deep purple-blue above, with a thick jet-black apical border on the forewing.  The female is steely blue, and generally unmarked on both wings above.  The underside is a hair brown with small and obscure dark spots and striae on both wings.  The tornal area of the hindwing has silvery-green markings.  There is a short stubby tail at vein 2 of the hindwing and another short tooth at vein 3.

This green-eyed species' caterpillars are usually found on the host plants co-existing with a species of ants.  The well camouflaged caterpillar has been successfully bred on at least three different species of Leguminosae in Singapore.  Both sexes are observed to open their wings to sunbathe at certain hours of the day, showing off their blue uppersides.

Text by Khew SK : Photos by Sunny Chir, Chng CK, Federick Ho, Khew SK, Henry Koh, Koh CH, Loke PF, Nelson Ong, Jonathan Soong & Horace Tan