The Yellow Flash (Rapala domitia domitia)
A Yellow Flash feeding on the flower of Syzygium sp.
As the month of October 2026 comes to a close, we look back at a rather hazy month that is reminiscent of the very polluted month in 2015 when the PSI indicator of air quality exceeded 200. Air quality is considered unhealthy when the PSI is above 100. During these times, the National Environment Agency (NEA) advises the public to cut down on outdoor activities, especially those vulnerable individuals suffering from respiratory conditions. However, over the course of this October, the PSIs were not as bad as previous years, but still hovered into the unhealthy range nevertheless.
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The annual haze is caused by the slash-and-burn agriculture practice in our neighbouring countries, and over the past two decades or so, the practice extends to the larger companies who needs to clear large tracts of land for oil palm cultivation. Whether or not the fires were deliberately started and who the culprits are, is often difficult to prove and when the fires spread, it is hard to contain, particularly during the dry months. Livelihoods and even lives are at stake, and there have been photos of the extreme polluted air in parts of Indonesia where the heart of the haze hotspots showing almost surreal and out-of-this-world landscapes with extremely hazardous air quality.
A Yellow Flash feeding in the flower of Mile-A-Minute
Singapore, being the "little red dot" is usually the victim and when the wind conditions are unfavourable, we will experience high PSIs and poor air quality. The only recourse the general public can resort to, is to stay indoors, limit exercise and outdoor activities and wear N95 face masks. In the last few days of October, the rains came, and the air quality improved somewhat as we hope for cleaner air days again.
Someone asked me if the haze and poor air quality affects butterflies. Whilst there hasn't been any specific research on this, anecdotal evidence of lower butterfly counts is quite evident. But the lower counts could also be due to the low seasons after the peaks from Mar to Jul each year. Hence there are currently no definitive evidence that the haze triggers a higher mortality rate in butterfly survivability. There is also speculation that the larger particles in the air affect the early stages of butterflies where the caterpillars, which breathe through spiracles along their bodies, could be choked by these particles.
A Yellow Flash perched on the flower of Syzygium sp.
Our Butterfly of the Month for October 2026 is the Yellow Flash (Rapala domitia domitia) which is often regarded as the largest species of the Rapala genus. The Yellow Flash is considered moderately rare and classified as "Near Threatened" in the Singapore Red Data Book 3rd edition. It is usually encountered singly, feeding on flowering plants or just perched on leaves amongst low level shrubbery and resting with its wings folded upright. When alarmed, it is skittish and takes off rapidly to the treetops.
A Yellow Flash feeding on the flower of a Spanish Needle
A Yellow Flash puddling at a sandy streambank
The Yellow Flash is predominantly a forest-depended species and usually stays within the sanctuary of the forested nature reserves in Singapore. Whilst its distribution is quite widespread around the forested areas and edges of the nature reserves, sightings are irregular. It is often encountered feeding at flowering trees like Syzygium or the fruits of the Singapore Rhododendron. There are rare occasions when males have been observed puddling at damp sandbanks.
A Yellow Flash showing its uppersides as it sunbathes on a sunny day
The Yellow Flash uppersides feature light brown wings with paler costal areas on the fore- and hindwings. The underside is a bright lemon yellow in pristine individuals and sparsely marked with jet-black markings on the forewings. The hindwings are generally unmarked with the exception of black tornal markings edged with metallic blue scaling. The tornal lobe is black with a hint of blue scales, and there is a filamentous white-tipped tail at vein 2 of the hindwing.
The eyes are jet black and smooth, whilst the antennae are black-and-white banded and the tips of the club of the antenna are orange. Its legs are also black-and-white banded. The caterpillar host plant in Singapore is currently unknown and will continue to be searched for.
Text by Khew SK : Photos by David Chan, Federick Ho, Khew SK, Henry Koh, Low JK, Low SC, Michael Soh, Jonathan Soong, Bene Tay, Yam TW and Angela Yeo.
