Pseudagrion microcephalum; Ceriagrion cerinorubellum; Ischnura senegalensis; Pseudagrion australasiae; Podolestes orientalis; Euphaea sp.

It is easy to recognise the larvae of damselflies. Compared to a typical dragonfly larva they are slimmer and less robust. More notably, damselfly larvae have three very distinctive caudal lamellae, also called external or larval gills, at the end of the abdomen. These are absent in dragonfly larvae.

The caudal lamellae have a variety of functions. They aid in respiration, function as fins during motion and can even break off in times of escape much akin to the discarded tail of a fleeing gecko. And just like a gecko’s tail, a larva can grow back its lost lamellae. The lamellae aid, but are not essential in respiration. Thus it is not unusual to see larvae missing one, two or even all of its lamellae just like the larva of Pseudagrion microcephalum below.
The shape and size of caudal lamellae will change as a larva grows. In many species, the lamellae will become smaller relative to abdomen length but expanding in width and more tracheated, hence having a bigger role in respiration.

Size, length, shape and patterns of caudal lamellae are essential tools in identifying species. Most damselfly larvae have lamellae which are flat and vertical like those of Ceriagrion cerinorubellum, Ischnura senegalensis and Pseudagrion australasiae. The brownish spots on the lamellae of C. cerinorubellum are examples of patterns which can occur.

Meanwhile, damselflies of the Euphaea species have their caudal lamellae in the form of swollen saccoids with a terminal filament.

Recently larva of the damselfly Podolestes orientalis is described. The species is from the family Megapodagrionidae and members from this family have their caudal lamellae in a horizontal plane. This character is unique to the family although not all species in the family have horizontal lamellae. I find the fan-like shape and banded patterns of P.orientalis lamellae very eye-catching. The larvae are now known to inhabit submerged leaf litter at the edge of shallow pools where they raised their abdomen upwards and have their lamellae splayed near the water surface. In this way, horizontal lamellae may be better adapted to aid respiration near the water surface in an otherwise low oxygen leaf litter forest pool. P. orientalis is a rather common species in our forests.

The larvae of many odonate species remain unknown and undescribed. Further discoveries will help scientists shed more light on the evolutionary history of this wonderful insect group.

Pictures taken at: Ex-situ, June 2009; September 2009; October 2009

References:

Choong, C. Y. & A. G. Orr, 2010, ‘The larva of Podolestes orientalis from West Malaysia, with notes on its habitat and biology (Odonata: Megapodagrionidae)’, International Journal of Odonatology, vol. 13(1), pp. 109-117.

Corbet, P. S. & S. J. Brooks, 2008. Dragonflies. HarperCollins Publishers, London, UK.

Kalkman, V. J., C. Y. Choong, A. G. Orr & K. Shutte, 2010, ‘Remarks on the taxonomy of Megapodagrionidae with emphasis on the larval gills (Odonata)’, International Journal of Odonatology, vol. 13(1), pp. 119-135.

Orr, A. G., 2005. Dragonflies of Peninsular Malaysia and Singapore, Natural History Publications (Borneo) Sdn. Bhd, Malaysia

Brahminy Blind Snake

Nature never fails to astound me. It is not always necessary to venture into forests to see some of the most amazing creatures, they can be right here in our backyard.
A gardening session by a colleague unearthed this incredible Brahminy Blind Snake (Ramphotyphlops braminus). This is one of the smallest snakes in the world, with a total length averaging about 13cm only. It is easily mistaken for an earthworm but trained naturalists will be able to tell it doesn’t have a segmented body. Instead the body is smooth, cylindrical and on closer examination, the presence of scales. And it is much more active than an earthworm is.

Apparently it is not blind but has tiny eyes. Eyesight is not of utmost importance since this snake spends its time burrowing in the dim world of root masses and soil, hunting small insects especially ants and termites. I tried to see the eyes under a microscope. It’s a thrill to see two black minute eyes staring back.

Another amazing aspect is this species is parthenogenetic, meaning females reproducing females asexually without fertilisation of eggs by males. In fact the Brahminy Blind Snake is an all female species. This is a common reproductive strategy in insects but not so in vertebrates. Some fishes, amphibians and of course snakes are known to be parthenogenetic.

This snake is said to originate from Sri Lanka or southern India, but is now very common in most regions including Singapore thanks to our horticultural practices. Though common and widespread, its ecology hides it away from humans most of the time making this wonderfully intriguing creature a hardly seen rarity…..…unless we start digging through all garden plots.
So if you are an avid gardener, do be gentle when encountering this snake. It is harmless, can be handled safely and is deserving of a home in our gardens.

Pictures taken at: National Biodiversity Centre, December 2009.

References:

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.

Wallach, V., 2008, ‘Range extensions and new island records for Ramphotyphlops braminus (Serpentes: Typhlopidae)’, Bulletin of the Chicago Herpetological Society

, vol. 43(5), pp. 80-82.

Tetracanthagyna larva

An impressive larva I’m currently rearing has provided very fascinating insights into terrestrialism in dragonflies larvae.
This aspect of larvae ecology is rather well known. There are several studies showing larvae inhabiting small streams or seepages in forest can have a diminished dependence on water. Some species in Japan live among wet rock and mosses beside streams, a species in Himalaya hang around wet ferns near waterfalls and one species from New Caledonia clings onto the underside of moist leaves away from any water body.

Closer to home, larvae of the genus Tetracanthagyna exhibits semi-terrestrial behaviour. Tetracanthagyna degorsi from Borneo apparently leaves the water at night to perch head down near water surface, seemingly to catch surface swimming fishes. T. waterhousei is another species with similar habits. There’s a picture of its larva catching a fish while completely out of water in the Field Guide to Dragonflies of Hong Kong 2nd edition (page 211).

The larva I have now also shows identical behaviour. Its hunting strategy is ambush. Most of the time it clings out of water with only the head partially submerged. From this position it waits, and when a shrimp moves near, wham! The forceful impact of its labium capturing the hapless shrimp fatally.
After capturing, the larva will occasionally move completely out of water to consume the prey. I notice the bigger the shrimp, the more likely it’ll move above water for consumption. And this becomes more frequent as the larva grows.
Those with a phobia for things creepy and crawly will find this larva utterly hideous. It is now almost entirely black, having adapted its colour to the surroundings; it currently measures about 6cm in length; and has a dragon-like frontal appearance. It might look monstrous but once emerged into adult, it will become the biggest dragonfly in the world in terms of wingspan and weight.

Tetracanthagyna plagiata is the only species from the genus recorded in Singapore so this larva should be of the species. I didn’t have the chance to establish its gender accurately so hopefully it’ll emerge into a male as very few male specimens of T. plagiata exists in museums worldwide. It should emerge very soon as it has stopped feeding for the past few days.

Pictures taken at: ex-situ, November, December 2009 & January 2010.


References:

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

Norma-Rashid, Y., L. F. Cheong, H. K. Lua & D. H. Murphy, 2008. The dragonflies (Odonata) of Singapore: Current status records and collections of the Raffles Museum of Biodiversity Research. Raffles Museum of Biodiversity Research, Singapore. 24 pp. Uploaded 07 Nov 2008 [http://rmbr.nus.edu.sg/raffles_museum_pub/Dragonfly_of_Singapore.pdf]

Orr, A. G., 2003. A Guide to the Dragonflies of Borneo. Their Identification and Biology. Natural History Publications (Borneo) Sdn. Bhd, Malaysia.

Orr, A. G., 2005. Dragonflies of Peninsular Malaysia and Singapore. Natural History Publications (Borneo) Sdn. Bhd, Malaysia

Wilson, K. D. P., 2004. Field Guide to the Dragonflies of Hong Kong 2nd edn. Agriculture, Fisheries and Conservation Department, Hong Kong SAR.

Kopstein’s Bronzeback (Dendrelaphis kopsteini )

A recent survey at the Central Catchment turns out to be one of the best I’ve had this year. Rare creatures sighted, good weather and good companions made a perfect morning in the forest. We spotted three snakes that day. The stand out has to be this Kopstein’s Bronzeback (Dendrelaphis kopsteini).
Also known as Red-necked Bronzeback, this species has always been confused with Elegant Bronzeback (Dendrelaphis formosus). It was only in 2007 that scientists sorted out the taxonomy and designated it as a separate species. We now know Kopstein’s Bronzeback can be distinguished from other Bronzeback snakes by its bright orangey red colour at the back of its neck. The species is widespread locally, being also present in rural or suburban areas. Although widespread, it is considered rare by Baker & Lim (2008) and has a status of vulnerable in the Red Data Book. Its distribution is from Thailand down to Peninsular Malaysia and Sumatra.

We were very lucky indeed to chance upon this individual consuming a lizard. When we first saw it, it had already captured the prey. After a brief struggle, the snake proceeded with lunch, swallowing the lizard in a matter of minutes. Our presence did not bother it at all thus enabling me to get a close video. Spotting creatures in the wild is always great but a window into the midst of their daily activity is unquestionably a huge bonus.

Kopstein’s Bronzeback is named after the Austrian herpetologist Dr. Felix Kopstein (1893-1939).

Pictures and video taken at: Central Catchment Nature Reserve, November 2009.

References:

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.

Vogel, G. & J. Van Rooijen, 2007. ‘A new species of Dendrelaphis (Serpentes: Colubridae) from Southeast Asia’, Zootaxa 1394: 25–45.

Neurothemis fluctuans; Trithemis aurora

How do dragonflies recognise members of their own species? Recognition of conspecifc is primarily through visual cues for dragonflies. They can recognise flight style, size, colours and patterns as well as ultraviolet reflection and optical density. The ability to recognise their own species is important as it enables dragonflies to defend territory and for a male to find the right female.

But sometimes, mistakes do occur. On a recent sunny morning in Singapore Botanic Gardens, a whole lot of dragonflies were active. There was about six species present and the area was buzzing. It seemed like an orgy was taking place as males grasped females for copulation and inseminated females were ovipositing. The males were also fighting each other for the females. Suddenly a tandem pair crashed onto a plant. A male Neurothemis fluctuans had grasped a female Trithemis aurora. The pair made several attempts to fly off but failed.

Tandem link between different dragonflies species is prevented because of the incompatibility between a male’s anal appendages and a different female’s head. It is like a lock and key system; the right key must fit the right lock. In this case, it is obvious the male N. fluctuans couldn’t grasp the female properly. After several tries, the male realised its mistake and released the female.
Both Neurothemis fluctuans and Trithemis aurora are very common species here. Both species are sexually dimorphic. Mature N. fluctuans males are reddish while the females are light brownish. For T. aurora, mature males are pink while females are yellowish.

Pictures taken at: Singapore Botanic Gardens, 2009; Toa Payoh Town Park, 2009 & 2008.

References:

Corbet, P. S. & S. J. Brooks, 2008. Dragonflies. HarperCollins Publishers, London, UK.