29 February 2024

Butterfly of the Month - February 2024

Butterfly of the Month - February 2024
The White Royal (Pratapa deva relata)

On this special once-every-four-years day of 29 Feb, we feature one of our "royal" butterflies from the Lycaenidae family. The Lycaenidae, often referred to as the Blues and Hairstreaks, is represented by the largest number of species in Singapore. As many of the species are cryptic and superficially very similar-looking, more species are being added to the Singapore checklist as new information becomes available, or observations of species which were previously missed are included to the list.

Our Butterfly of the Month for February 2024 is the moderately rare White Royal (Pratapa deva relata). This species was a recent re-discovery back in 2007 when it was first photographed at an urban area near Telok Blangah Hills Park. It was subsequently observed that the caterpillars of this species depends on the parasitic mistletoe, Rusty Mistletoe (Scurrula ferruginea) as its host plant. With a more targeted observation of habitats where this parasitic plant grows, it was observed that the species is often present in the vicinity of the host plant.

The White Royal is widely distributed across Singapore and found in urban parks and gardens, as well as the nature reserves and areas where the caterpillar host plant can be found. The distinctive parasitic plant can often be spotted growing on other plants where its "rusty" undersides of its leaves stand out. The adult butterflies are often spotted singly where they occur, but females have been seen in small numbers, ovipositing on its host plants.

Male (top) and Female (bottom) White Royal showing their upperwings

The upperside of the male White Royal is a deep lustrous blue with broad black borders, particularly at the apical area, on the upperside of the forewings and a series of black marginal spots on the hindwings. The females feature paler blue uppersides, also with broad black apical borders on the forewings.

A female White Royal sunbathing with open wings
A "rear view" of the White Royal showing its tornal lobe

The underside of both sexes is greyish white with a series of post-discal narrow black streaks. The underside of the hindwing has a prominent orange-crowned black marginal spot in space 2. There is a pair of white-tipped tails at the ends of veins 1b and 2. The tornal lobe on the hindwing is black and orange with white cilia on pristine individuals.

The eyes of the White Royal are transparent instead of jet black, as in the case with many of the related species. The legs are greyish-white throughout. The antennae are black-and-white banded, and orange tipped at the club.

A female White Royal resting on the leaf of the Rusty Mistletoe after ovipositing

The complete life history of the White Royal has been successfully recorded in Singapore on its single caterpillar host plant, the Rusty Mistletoe (Scurrula ferruginea). This host plant, one of only a few parasitic and hemi-parasitic plants found in Singapore, is featured in an earlier blogpost about Mistletoes and their importance to the butterfly fauna in Singapore. At least 4 species of Lycaenidae caterpillars depends on the Rusty Mistletoe for survival and continued existence in Singapore.

Text by Khew SK : Photos by Khew SK, Loh MY, Richard Ong, Horace Tan, May Yap and Yip Jen Wei