31 March 2010

Dazzling Dragonflies of Singapore!

Rapacious predators on gossamer wings, these jeweled aerial acrobats play a key role in the habitat and are a delight to observe.
Crimson dropwing by Tang Hung Kei

A study of Singapore's dragonflies and damselflies reveals that we have now more than 120 species (124 to be precise)! This is as large as the number in the whole of Europe.

What's special about Singapore's dragonflies?

A two-year survey found that despite Singapore's highly urbanised environment, one third of all our dragonflies can still be found in our parks. 40 species were found living in our park ponds with the majority at key locations such as Bishan Park, Kent Ridge Park, and Toa Payoh Town Park.

In fact, a rare damselfly species, Pseudagrion rubriceps, was found at Toa Payoh Town Park! This was first recorded in Singapore by a single specimen from the nature reserves in 1993. 18 species have been recorded in this park.
Photo by Leslie Day on Tang Hung Bun's website

In addition, Bishan Park is the only urban park that harbours two damselflies, Ceriagrion chaoi (first recorded in Singapore in 2005) and Pseudagrion austalasiae, which have previously been known to exist only in the nature reserves.

The two-year study by NParks involved volunteers, naturalists and dragonfly specialists from our universities and special interest groups. They conducted surveys of 19 parks, as well as the nature reserves, and covered more than 30 freshwater habitats ranging from small ponds to lakes and streams. In addition to collecting baseline data on the dragonflies, they also linked the results to information about plants and water quality at each site. This gives a good picture of the requirements for each species.

What does this mean?
It shows that NPark's efforts over the years to integrate wild areas into urban parks have paid off. The dragonfly study will now help NParks further enhance and protect dragonflies, and create new habitats for them. For example, rather than having boring monotonous open water, a variety of habitats can be provided in future parks using different plants as well as ponds of different depths, to enable dragonflies to thrive.

What is a dragonfly?
You can learn more about our dragonflies and damselflies from Tang Hung Bun's awesome Singapore Odonata website with checklists, gorgeous photos and more; and Robin's field stories and observations on his fabulous Creatures Big and Small blog.

Like many insects, dragonflies and damselflies undergo metamorphosis. A young dragonfly looks nothing like the glorious winged adult. A typical dragonfly spends its larval stage near or submerged in freshwater. Its wingless form is often hideous and repulsive, resembling evil alien monsters depicted in movies.
It is a voracious predator, striking terror among its prey which includes small fishes. Here's an awesome photo of the larva of Tetracanthagyna that Robin studied. In its ferocious jaws is a shrimp. Tang Hung Bun has a video clip of a larva devouring a fish!

Eventually, this monster of the water transforms into a creature of the air! Robin shared the results of his arduous observation of this miraculous transformation in Orthetrum chrysis. As he describes it so well, "Just like an ugly duckling, its wings open and transformed into a beautiful reddish female".
The adult dragonfly is also a predator! As Tang Hung Bun shares, the adult has "strongly biting mouthparts and are active and aggressive carnivores, preying mostly on other insects. They catch insects on the wing." They can catch and eat insects bigger than themselves! Robin has stories and video clips of some in action. They are indeed fearsome 'dragons' of their realm!

Nature's little jet-fighters, these insects are sleek and snazzy: like this gorgeous Scarlet Pygmy by Tang Hung Bun. And they have the top-of-the-line equipment needed for life in the fast lane.
Humungous eyes, each containing up to 30,000 individual lenses, so they can react to activities more than 10 metres away. They have two pairs of wings. As Tang explains on his website, they "can flap or beat their wings independently. This means the front wings can be going down while the back ones are coming up. Dragonflies are excellent fliers, hover and fly backwards quite easily". Robin shares more about how dragonflies fly, and may sometimes gather in groups to forage on flying insects.

Mating is what being an adult is all about. And mating in dragonflies is a complicated business. Before inserting his sperm, the male usually scrapes out any sperm that is already existing in the female's special "sperm container". Robin shares all the gruesome details of sperm displacement in this post. But she in turn can still choose which sperm to use. So mating can take a long, long time. Robin shares more in this post.

Mating dragonflies and damselflies form a typical 'circle' when they mate. There is a 'lock and key' system between the male and female of the same species. This makes it impossible for different species to mate, as Robin's post of a case of mistaken identity shows. The male and female dragonfly can look very different, as this pair of Variable wisps by Tang Hung Bun illustrates.
Males are territorial and have fights over good spots, as Robin's post shares.

After the mating, the female lays her eggs on submerged vegetation. Robin shares a video clip of one female going underwater to lay her eggs, and a video clip of a female flying at high speed, literally firing off her eggs into the water. Awesome! Some dragonflies cut a slit into vegetation to insert their eggs, as Robin's post shares.

Of what use are dragonflies to people?
Dragonflies (like all nature's creatures) have their role in the ecosystem. And of course are 'useful' whether humans are present or not. As predators, both as larvae and adults, they keep the populations of their prey in check. And thus help maintain the balance of nature.

People will inadvertently find it useful that dragonflies control the populations of disease-bearing insects like mosquitoes. As dragonflies depend on good quality freshwater to survive, their presence is also an indicator of water quality. Being colourful and active, they "now form a new type of visitor attraction in the parks."

Dragonflies teach a lot to those who take the time to observe them.

Natural flyers like birds, bats and insects outperform man-made aircraft in aerobatics and efficiency. A dragonfly, researchers found, has remarkable resilience to wind, considering how light it is. This is attributed to its wing structure and flight control. (Birds, Bats And Insects Hold Secrets For Aerospace Engineers ScienceDaily Feb. 9, 2008) Another scientist points out that the best way to learn about flight is by first looking at what happens naturally. By understanding the dragonfly's flight, engineers hope to use these ideas to build a flapping machine as efficient as a fixed-wing aircraft (Scientist Uses Dragonflies To Better Understand Flight ScienceDaily, Feb. 21, 2006)

Indeed, a prototype flapping machine was revealed that weighed only 3 grammes. It looks very much like a dragonfly!
The basic principle of the DelFly is derived from nature. The 'dragonfly' has a tiny camera (about 0.5 grams) on board that transmits its signals to a ground station. With software developed by TU Delft itself, objects can then be recognised independently. The camera transmits TV quality images, and therefore allows the DelFly II to be operated from the computer. It can be manoeuvred using a joystick as if the operator was actually in the cockpit of the aircraft. (Micro Air Vehicle: Three Gram 'Dragonfly' Takes Flight ScienceDaily, July 23, 2008)

Dragonflies can even shed light on human diseases! A study found that dragonflies infected with parasites suffer the same disorders that have led to an epidemic of obesity and type-2 diabetes in humans. The study found links between metabolic disease to a supposedly harmless parasite living in the dragonfly's gut. The parasites belong a group of microorganisms that includes protozoa, which cause diseases like malaria and cryptosporidiosis. The microbes disrupting the dragonfly metabolism may hold clues for scientists looking for the root causes of metabolic diseases in humans.(Dragonfly's Metabolic Disease Provides Clues About Human Obesity ScienceDaily, Nov. 21, 2006)

Dragonflies in Singapore
Dr Geoffrey Davison, Assistant Director at NParks' National Biodiversity Centre, said:"Singapore is located within a region of high dragonfly diversity. It is particularly exciting when we can see biodiversity in the places where we live or visit for recreation, like parks. We are thrilled to discover that many of the common species have adapted to ponds and wetlands in our parks and gardens. We are even more intrigued to learn that many of Singapore's parks have become refuges for rare species of dragonflies. We believe that the wide spread of parks through Singapore's landscape; the large variety of ponds and other waterbodies inside the parks; and conscientious management of water quality are key reasons for the dragonflies' presence."

He concluded, "Urban parks do play an important role in dragonfly conservation. The results of this two-year study are valuable insights for us in our planning and development of parks, current and future, so that we create suitable habitats where the dragonfly population can thrive. The information will also be relevant to other agencies managing water, drains and ponds in Singapore, or anyone who owns a pond."

What's next?
NParks is currently working on a book to document the dragonfly project findings and to further share with the public about the dragonfly diversity in Singapore's parks and gardens. This will be published by the end of the year.

We can also look forward to a photo identification fieldguide of dragonflies with Tang Hung Bun as the main author. This will surely be invaluable those wanting to learn more about our dragonflies!

In addition, NParks will also be publishing "A Selection of Plants for Greening of Waterways and Waterbodies in the Tropics" next month. This book, which is the first of its kind, features plants suitable for aquatic landscapes in the tropics, including a selection of plants that can attract dragonflies, cleanse the water, and absorb specific chemical elements from the environment.

Some members of the dragonfly project team are due to give a workshop for nature guides at the Leafmonkey Workshop. Join the Leafmonkey Workshop facebook page or subscribe to the blog to get updates!

Meanwhile, go out and observe our dragonflies. With renewed respect for these awesome predators!

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