Sunday, January 16, 2011

Barred Kukri Snake, Striped Kukri Snake

Snakes of the genus Oligodon are commonly known as Kukri snakes. They are so-named due to the curved hind fangs at the back of their mouth. Those fangs evolved to suit Kukri snakes’ diet of chiefly eggs. As the eggs are swallowed, they would be pierced open by the special fangs. The fangs’ shape reminds one of the famous Kukri knife used by Nepalese.

Singapore has three types of Kukri snakes: Brown Kukri (Oligodon purpurascens), Striped Kukri (Oligodon octolineatus) and Barred Kukri (Oligodon signatus).

Of the three, Striped Kukri snake is the most common and can inhabit suburban areas. Sometimes road kills are encountered, like this poor soul from 2006.

The other two species prefer forests in the nature reserves and thus rarer. Local books list them as ‘restricted to a few areas and rare’ and ‘critically endangered’. Perhaps of the two species, Barred Kukri snake is of more significance because Singapore is the type locality and knowledge on its biology is scarce.

So it was with great pleasure that a Barred Kukri snake was seen recently during a survey. The bright reddish-brown bands on its back are certainly attractive. And as the cameras clicked away, this elusive forest dweller slowly slipped back into the forest darkness. Thus ending a rare glimpse into another one of nature’s mysteries.

Pictures taken at: Eng Neo, June 2006; Central Catchment Nature Reserve, December 2010.


Baker, N. & K. K. P. Lim, 2008. Wild Animals of Singapore. A Photographic Guide to Mammals, Reptiles, Amphibians and Freshwater Fishes, Draco Publishing and Distribution Pte Ltd, Singapore.

Davison, G. W. H., P. K. L. Ng & H. C. Ho (eds), 2008. The Singapore Red Data Book: Threatened Plants and Animals of Singapore. 2nd Edition. The Nature Society (Singapore), Singapore

Sunday, January 02, 2011

Agrionoptera insignis , Agrionoptera sexlineata

Different dragonflies species adopt different survival strategy during the vulnerable stage of metamorphosis and emergence from larva to adult. The majority of species leave the water either partly or completely before emergence. This behaviour is most likely meant to expose the thoracic spiracles to air respiration. But the amount of time a pharate adult (one that has changed from larva to adult but still within the old larval skin) spent outside of water before emergence varies. For most species, the time spent is usually on the day before emergence but some species have been known to stay out of water for up to 14-20 days. I’m not exactly sure the reasons behind this time variation and haven’t read up enough literature on this aspect of dragonflies biology. Thus recent emergence of two closely related species is interesting to note.

The first to emerge is Agrionoptera insignis (Grenadier). The larva was completely out of water for up to three days. During this time, it explored various spots on the driftwood, usually resting at a spot (blue arrows) for a few hours before moving on. In those three days, it seemed to be selecting an emergence spot meticulously. Either that or some parts of the larva was still undergoing changes to adulthood and so not yet ready for emergence.

Emergence into an adult female finally occurred on the fourth day.

Next up is a close relative from the same genus: Agrionoptera sexlineata (Handsome Grenadier). For this larva, the emergence was quick and straightforward. I spotted it out of water at early evening and by the next morning, the fine-looking adult male has emerged.

Its interesting how two similar and related larvae assumed different pre-emergence behaviour. But this is just a one-off observation and thus can’t constitute any concrete conclusion. Hopefully future larvae studies by other odonatologists can provide clearer understandings. The larvae emergence of both species is captured beautifully by Dr. Choong here:

Agrionoptera insignis (Grenadier)

Agrionoptera sexlineata (Handsome Grenadier)

Although both A. insignis and A. sexlineata are listed as uncommon in the Singapore dragonfly book, the former is definitely more often encountered in the field and widely distributed while the latter species is more localised.

A. insignis female

A. sexlineata male

Pictures taken at: ex-situ, December 2010; Central Catchment Nature Reserve, August 2009 & December 2010.


Corbet, P. S., 1999. Dragonflies: Behaviour and Ecology of Odonata. Cornell University Press, New York.

Tang, H. B., L. K. Wang & M. Hämäläinen, 2010. A Photographic Guide to the Dragonflies of Singapore. Raffles Museum of Biodiversity Research, Singapore.