The White Fourline Blue (Nacaduba angusta kerriana)
A White Fourline Blue perched on a leaf in the forest understorey
We are into the 2nd half of the year 2025, and the summer is in full swing in the northern hemisphere. The weather has been mercilessly hot but yet there have been countries that have been inundated with heavy rains and even suffered fatalities. Over in Singapore, it has been a very hot July with few days of rains in between and we are getting temperature highs in the mid-30's for the month.
A newly eclosed White Fourline Blue perched on its pupal case
It was alarming that even over in our generally peaceful ASEAN region, disputed territorial claims have led to a war level conflict between Thailand and Cambodia. The military on both sides exchanged fire at the border between the two neighbours and escalated to heavy artillery, rocket fire and air strikes on 24 July. There were fatalities, unfortunately affecting civilians where up to 43 people were killed in the crossfire. Ceasefire talks are in progress, although tensions remain high.
It was a generally uneventful month in Singapore, perhaps except for a sinkhole incident that swallowed a car. Fortunately, the lady driver managed to get out of her car and was rescued by some migrant workers from a construction site adjacent to the sinkhole before a burst water mains flooded the hole. The authorities are still investigating the cause of the soil failure and the road remains closed to traffic whilst repairs are in progress.
A mating pair of White Fourline Blue
Over in the US, the topic of tariffs, threats and negotiations are still ongoing with many countries as the deadline of 1 Aug looms. Many trade representatives are pushing negotiations hard to ensure that the proposed tariffs are not imposed on their countries' goods to the US. Despite the volatility and uncertainty, world financial markets appear to be still on a bull run as if these tariffs have been already factored into their projections.
Back to our Butterfly of the Month for July 2025 - a diminutive but extremely rare Lycaenidae called the White Fourline Blue (Nacaduba angusta kerriana). It was re-discovered in late 2008 at Telok Blangah Hills Park when the late ButterflyCircle member Sunny Chir stumbled on a mating pair along the trails and suspected that it was a species that he had not encountered before. Subsequent trips to the location continued and for a few days, the species was flying in the same area.
The White Fourline Blue was on the early authors' checklists but has eluded butterfly watchers until that year. However, besides that very short period, it has been absent again and never reliably seen since. Classified as 'data deficient' in the Singapore Red Data Book 3rd Edition, its mysterious appearance, and disappearance is still unexplainable. Perhaps it is still flying around somewhere in Singapore just waiting to be encountered again someday soon.
Upperside of male White Fourline Blue (top) and female White Fourline Blue (bottom)
The male White FourLine Blue is purplish blue above with a thin black border, which is about 1mm broad towards the apex. The hindwing is unmarked but with a thin submarginal black border. The hindwing cilia is white. The female has broad black border on the forewing and has a light blue ground colour with diffuse greyish markings on both wings.
Beneath, both sexes have greyish ground colour with very broad and diffuse whitish-grey stripes. On each hindwing, there is an orange-crowned tornal spot lightly speckled with bluish-green metallic scaling. i Next to the tornal spot, a pair of filamentous white-tipped tails occur at end of vein 2. Marginal and submarginal spots are black and stand out against the whitish background. The prominent rounded black sub-marginal spot in space 6 of the hindwing serves as an important identification key for this species.
A White Fourline Blue puddling on damp muddy footpath
The White Fourline Blue has an erratic but rather weak flight, and prefers to stay under shade, fluttering amongst thick vegetation along the forest edge. Males tend to stay higher up in the forest canopy, and descend lower to find a mate, or to feed. Males are also observed puddling on damp forest paths in Malaysia.
A female White Fourline Blue ovipositing on its caterpillar host plant, Entada spiralis
Text by Khew SK : Photos by Sunny Chir, Khew SK, Low JK and Horace Tan.
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