24 July 2010

Butterfly of the Month - July 2010

Butterfly of the Month - July 2010
Horsfield's Baron (Tanaecia iapis puseda)

The month of July is famous in that it is the only month of the year that was first named after a human being - Julius Caesar in 46 BC. The month has 31 days, and in the northern hemisphere, it is usually the peak of the summer months and is the hottest month of the year.

However, in Singapore, like in 2009, the weather has been rather wet - exceptionally wet actually, where floods occurred persistently following some of the wettest days on record. It had some residents up in arms when flood waters inundated their homes and commercial premises more than once during the month! A symptom of global warming and climate change? We'll have to wait and see. In the meantime, park your cars on high ground!

If the first of July be rainy weather,
It will rain, more or less, for four weeks together.
Source: English Proverb

Despite the rainy weather, our butterfly friends continue to thrive. A moment's respite from the bad weather will see our winged jewels up and about, feeding hungrily at flowers and other sources of food.

This month, we feature the sexually dimorphic species, the Horsfield's Baron (Tanaecia iapis puseda). This species prefers the sanctuary of the forested areas in Singapore, although they are sometimes found in public parks and gardens. Males are more often seen than females. The male of this species exhibits 'territorial' behaviour, where it perches on a few favourite locations and dives to chase away any intruders into its space - even a stone thrown into its domain of supervision will be similarly chased away!

The male Horsfield Baron is a rich velvety black above with a broad bright blue marginal border on the hindwing and reaching the tornal area of the forewing. The underside is a pale buff with light brown markings.

The female is a pale ochreous brown resembling the Malay Viscount. The submarginal “V” shaped markings are less distinct than those of the associated species. In some individuals, light blue washes can be more distinct on the wings, especially on the white areas of the wings.

The male Horsfield Baron has a flap-glide flight and is skittish and alert to movements. Often, individuals are encountered where they return persistently to a few favourite perches time and again, even after being disturbed. It appears to prefer stopping to rest with its wings opened flat rather than with its wings closed upright. Very rarely, males have also been observed to puddle at roadside seepages.

A male Horsfield's Baron puddling at a roadside seepage

The female, on the other hand, is usually found flying amongst shrubbery and particularly its preferred caterpillar host plant - the Singapore Rhododendron (Melastoma malabathricum). The female is more often found feeding on flowering plants, rotting fruit and the ripened fruit pods of the Singapore Rhododendron.

The caterpillar is unique in appearance, with its 'spiky' processes making it appear much larger and sinister than it really is. It is actually quite harmless.

Where the species is found, sometimes several individuals are encountered. Whilst it cannot be said to be common, the Horsfield's Baron makes a regular appearance in many parts of the nature reserves and even in public parks and gardens.

Text by Khew SK ; Photos by James Chia, Sunny Chir, Federick Ho, Khew SK, Koh Cher Hern & Sum CM

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