31 March 2024

Butterfly of the Month - March 2024

Butterfly of the Month - March 2024
The Indigo Flash (Rapala varuna orseis)

A pristine female Indigo Flash perches on a dew covered grass blade in the early morning hours. Note the slight purplish wash on the wing bases.

March 2024 has whizzed past in a flash, and on this final day of the month, we feature one of our "Flash" butterflies that exists in Singapore. A butterfly that belongs to the Lycaenidae family, called the "Blues and Hairstreaks", these species found in Singapore are mainly classified under the genus Rapala. The Flash butterflies are fast-flying skittish species and are difficult to spot when they flash from perch to perch.

Our feature butterfly for March 2024 is the Indigo Flash (Rapala varuna orseis). It is one of nine extant species from the genus Rapala that have been found in Singapore. Only recently, the early stages of the species were recorded on the local caterpillar host plant, Bridelia tomentosa. The Indigo Flash is often encountered in urban parks and gardens as well as within the nature reserves of Singapore.

The species is skittish and is usually quite alert. It is widely distributed across Singapore, where it is regularly encountered singly but at times more than one individual is spotted in the same location. At certain hours of the day, both sexes are sometimes observed perched on the uppersides of leaves with their wings opened almost flat to sunbathe.

Upside-down behaviour of both sexes of the Indigo Flash where the butterfly perches upside down on leaves and stems

It is sometimes encountered feeding on flowering plants and weeds like Mile-A-Minute, Spanish Needle and Stringbush. When it is resting in the shade, the Indigo Flash sometimes displays an upside-down behaviour where it perches on the undersides of leaves to rest. Both males and females are observed to behave this way.

A female Indigo Flash perched with open wings to sunbathe
A male Indigo Flash showing a glimpse of its deep indigo-blue upperside 

The Indigo Flash belongs to the varuna group of the genus Rapala, where the males and females are a shade of blue or bluish-green on the upperside. Males of the Indigo Flash is indigo blue above and unmarked, whilst females are steely blue and also unmarked. The underside is dark brown in the male and is strongly purple-washed. The female is a lighter brown and usually lacks the purple wash found in the males.

The post discal bands are white-edged, and broader than usual compared to other species in the genus, and darker than the ground colour of the underside. There is a large orange-crowned eyespot at the tornal area of the hindwing, with iridescent blue-green scales adjacent to it. On the hindwing, the cell-end bar is angled towards the post-discal band and closer, often touching each other. There is a white-tipped black filamentous tail at vein 2 of the hindwing.

Note the circular disc on the underside of the hindwing that houses the scent brand in the male Indigo Flash

The eyes of the Indigo Flash are jet-black and smooth. The legs are black-banded. The antennae are also black-banded and orange-tipped at the antennal club. There is a scent brand within space 7 on the hindwing and appears as a prominently raised circular disc on the underside of the males of the Indigo Flash.

Text by Khew SK : Photos by David Chan, Khew SK, Horace Tan, Bene Tay and Mark Wong