01 October 2016

Butterfly of the Month - October 2016

Butterfly of the Month - October 2016
The Plain Tiger (Danaus chrysippus chrysippus)

It's the eighth month of 2016 already! Celebrated across the world wherever there are Chinese communities, the Mid-Autumn Festival (Zhong Qiu Jie) falls on the 15th day of the eighth lunar month of the Chinese calendar (although this actually fell in Sep according to the Gregorian calendar). This coincides with the autumn equinox when the moon is at its roundest and brightest. It is a time for family and friends to gather with their colourful lanterns and to admire this beautiful sight and give thanks for harmony, happiness and the fullness of life.

It was also a time where offerings of mooncakes and pomelos are made to the moon. In modern times, however, mooncakes come in more creative (but fattening!) forms from durian and chocolate fillings to multi-coloured snowskin and quadruple preserved eggyolk varieties. There were even recent comparisons of how many calories one would consume in a mooncake, compared to Singapore's local gastronomic delights (of the 'sinful' types like char koay teow, chicken rice and roti prata). No matter, this once-in-a-year indulgence is probably worth it!

The previous month also saw an unprecedented weather phenomenon in the most powerful typhoon recorded in 2016, called Meranti. With estimated wind speeds of up to 285 km/h, the super-typhoon struck the Philippines, Taiwan and China, causing widespread damage and fatalities. Hot on the heels of Meranti, another typhoon, Megi, albeit less powerful, made landfall in Taiwan, smashing into the island and causing at least four deaths and numerous injuries.

In Singapore, we saw the ninth edition of the Formula 1 Singapore Grand Prix. Reputed to be the only night F1 race in the world, the 2016 Singapore GP saw German Nico Rosberg on the winner's podium. One wonders if the interest in F1 waning in Singapore, as it was reported that ticket sales for 2016 was possibly the lowest ever, since the F1 came to Singapore in 2007. Nature buffs were treated to a sight where a Water Monitor ran across the F1 track and caused some ruckus amongst the race officials.

Back to nature, and we feature October's Butterfly of the Month 2016, the Plain Tiger (Danaus chrysippus chrysippus).  This common but pretty butterfly has become a dominant species in our urban butterfly gardens where its caterpillar host plants, the Blood Flower (Asclepias currasavica) and the Crown Flower (Calotropis gigantea) are cultivated. At times, it can almost be considered abundant, as many Plain Tigers flutter freely amongst the nectaring plants.

Back in the mid-90's when I was participating in butterfly biodiversity surveys with the National Parks Board, the Plain Tiger was not as common as it is today. One might even consider the species a relatively rare species, as few individuals were sighted. Today, with the widespread cultivation of its caterpillar host plants in urban gardens, the Plain Tiger is now a regular feature species in many of these butterfly gardens.

The Plain Tiger has rich fulvous orange forewings with a broad black apical border bearing a series of white spots. Two forms occur in Singapore - form-chrysippus, where hindwings are unicolourous with the orange forewings; and form-alcippoides, which has white hindwings. The white-hindwinged form is by far the commoner of the two forms in Singapore.

Whilst it is considered common, the Plain Tiger tends to be quite local in that it is always found not far from where its caterpillar host plants are cultivated. It is seldom seen in the forested nature reserves and is more of an urban butterfly species.

Like many other species of the Danainae sub-family, the Plain Tiger displays aposematic colouration which advertises its impalatability to would-be predators. It serves as a model to the female of the Danaid Eggfly (Hypolimnas missippus missippus). The latter species has been found in Singapore, but extremely rare. However, thus far, there is no sighting of the female of the Danaid Eggfly in Singapore.

The Plain Tiger flies with a slow and unhurried flight, fluttering from flower to flower and frolicking amongst other individuals of the same species. It is partial to the semi-dried plant of the Indian Heliotrope (Heliotropium indicum). The male Plain Tiger is also attracted to the Rattlebox Pea (Crotalaria retusa), where it claws the pea pod and then feeds on the fluids that the damaged pea pod exudes.

The male Plain Tiger can be distinguished from the female by an extra 'sex brand' on the hindwing. The white spot which is surrounded by black ring, is quite distinct and obvious and easily tells apart the males from the females. This spot, which bulges slightly, consists of a cluster of specialised scent scales used to attract females.

The colourful caterpillar feeds quite openly and can defoliate the host plant quite quickly. As the caterpillars sequester the poisonous sap from the host plant, they are distasteful to predators and birds tend to leave them alone.

Text by Khew SK : Photos by Bob Cheong, Sunny Chir, Chng CK, Brian Goh, Khew SK, Loke PF, Bobby Mun, Anthony Wong, Mark Wong and Benjamin Yam