Males of dragonflies and damselflies are especially adapted to displace the sperm of the previous male from a female. The discovery of sperm displacement in odonates by Prof. Jonathan Waage in 1979 is considered a significant finding in odonatology. Since then, it is now known there are four distinct ways a male can displace a rival male’s sperm: 1) physical removal by means of hooks or horns on the penis; 2) moving rivals’ sperm to sites in the females where its least likely to be used; 3) stimulation of female to induce sperm expulsion; 4) flushing out of rival’s sperm using the copulating male’s sperm.
These are fascinating behaviours. An earlier post mentioned this casually. Recently, I observed the copulation of Devadatta argyoides, enabling me a better understanding of sperm displacement.
Devadatta argyoides is from the family Amphipterygidae. This is a small and primitive family with only one species present in Peninsular Malaysia and Singapore. In fact Singapore is the type locality for this damselfly. It is rather common and usually found perching near small forest streams.This couple had just gotten into tandem when I first spotted them. The male then flew with the female in tow for a short distance before perching above the stream. Slowly the female bent her abdomen to form the 'wheel’ thus interlocking their genitalia.
Almost immediately, the male started displacing rivals’ sperm. This can be seen clearly by the male abdomen’s active movement. It lasted for about 2-3 minutes before the male stopped moving to transfer in his own sperm.After copulation, the couple separated with the female flying off a distance away. The male did not seem interested in mate guarding nor did the female oviposit after I followed her for almost 10 minutes. I’m not familiar with the mating system of D. argyoides. Perhaps during this post-copulatory rest, the female was assessing the male’s guarding capacity, or the suitability of ovipositing site, or she’s manipulating the recently received sperm for fertilisation and evaluating its quality. 
The mating systems in odonates are varied with six systems currently recognised by scientists. There are lots more to discover on odonates mating behaviour especially species rarely encountered due to their elusive nature.
Pictures and video taken at: Bukit Timah Nature Reserve, October & November 2008
References:
Corbet, P. S. & S. J. Brooks, 2008. Dragonflies, HarperCollins Publishers, London, UK.
Lieftinck, M. A., 1954. ‘Handlist of Malaysian Odonata’, Treubia, vol 22, pp. 1-202.
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
As forests degradation occurs, silt and sediments become accumulated causing streams to flow slower thus making it a more suitable habitat for V. amethystina. Historical records show that V. amoena was once found in Ulu Pandan. This is a perfect case in point of how much forests we have lost and how vulnerable forest damselflies are. 
Few months back, an Asian Toad (Duttaphrynus melanostictus) made an appearance in my office. More precisely, it paid homage to a small corner. It was certainly a strange one. Throughout the whole time, it just sat there facing the wall with a contemplating look. It seemed overwhelmed by the wall and can’t decide what to do next. And it just stayed there the whole day and was so engrossed it totally ignored the mosquito sucking blood from its lower back.
There must be a scientific reason why it chose to sit at the corner throughout the day. But animals do strange things. Not all behaviour has to be explained and it is this erraticism that makes wildlife so fascinating.
Within this family, the genus Drepanosticta is represented by eight species in Peninsular Malaysia. They usually fly close to streams, flitting within the forest understory. Both males and females typically have a blue spot at the abdomen base in which the shape of the spot can serve to identify some of the species from Peninsular Malaysia. 
Drepanosticta quadrata has a blue spot with a triangular pointed tip. This species was described from Singapore and according to references is known only from Singapore. This would thus make this damselfly a Singapore endemic. Even so, the website 
Many inter-tidal inhabitants are small. This octopus, with its arms fully extended, would be about the size of my two palms. For many people, all they see of octopuses is a blotch of black ink as the animal retreats into their hiding places at the first sign of danger. But any observer with patience and sensitivity will no doubt be rewarded with glimpses into the lives of our inter-tidal Singaporeans.
This is a Robber Fly from the Order Diptera (true flies). True flies are distinguished from other flying insects by having only a single pair of wings while their hind wings are greatly reduced into flight balancing organs called halteres. Robberflies belong to the Asilidae family but we are not sure what this particular species is.
Not sure how well robber flies are studied in Singapore. But unsurprisingly, there’s tons of information on the web. This website 
Perhaps the elders from the documentary would be glad to know “kilah” can still be found in our waters.
Another odonate survey with the gang, this time to the ponds of Marina East. The habitat is dominated by thin grass-like vegetation. Not very sure what plant it is but most probably belongs to the Cyperaceae family. The water itself is full of brownish algae and there’s a slight smell typical of eutrophic waters.
Nevertheless, this is an excellent habitat for odonates. They are in high abundance and are very active thanks to the warm morning sunshine. The most numerous species is Diplacodes nebulosa. They are very distinct due to the dark tips on their wings. All the males are defending a small territory and chasing each other, zipping all over the water surface.
The most striking dragonfly there has to be Rhyothemis triangularis, aptly named due to the deep metallic blue triangular patch on its hind wings. Dragonflies from the genus Rhyothemis characteristically have short abdomens with broad hind wings. Some of them are quite common in open countries or streams in swampy forest. R. triangularis is common and widespread in Asia. However in Singapore they are rather uncommon as habitats akin to the Marina East ponds are few and far between.
But odonates are not the only creatures inhabiting the ponds. From afar, a Lesser Whistling-duck (Dendrocygna javanica) made an appearance. This is a nationally vulnerable bird. Once again habitat loss is the main cause as freshwater ponds are destroyed when urbanisation encroaches. This bird has an estimated population of 250 in Singapore.
As we left Marina East, I sensed a “melancholy in the wind and sorrow in the grass” (Charles Kuralt). How much longer will this location remain as it is? Its neighbour at Marina South is already morphing into the Integrated Resort. Rumour has it that Marina East will become a golf course. “Another golf course?!” Tang sighed.
The scenic Kranji Marshes hug along much of Kranji Reservoir’s perimeter. Marshlands are an increasingly rare habitat in Singapore as many have been lost to urban development.
Purple Swamphen is a member of the Rail family which also includes the more common White-breasted Waterhen (Amaurornis phoenicurus). They inhabit mostly swampy and marshy habitats. These birds have a clearly distinguishable robust stout body, short tail and are rather weak fliers. Their huge red bill, red frontal shield, red legs and purplish-blue plumage make them one of Singapore’s most attractive marshland birds.
Purple Swamphens have a very conspicuous white undertail covert. The birds will constantly flash this white rump patch by jerking their tail up and down. Research suggests that this behaviour is a form of prey-predator communication whereby a bird’s state of alertness is communicated to a potential predator, thus discouraging the predator from a vigilant prey. Perhaps that was exactly what the bird was trying to tell us that Christmas afternoon. We certainly would not have the heart to harm such a fine-looking creature. 