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:

http://odonata-malaysia.blogspot.com/2009/05/emerging-agrionoptera-insignis.html
http://odonata-malaysia.blogspot.com/2009/01/agrionoptera-sexlineata-larval.html

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.



References:

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.

Singapore dragonflies & their African relatives

Three months back, I was on work assignment in Nairobi Kenya for 13 days. Most of the work time was spent in the United Nations compound. Within the huge UN complex, many artificial but well vegetated ponds exist. It thus gave me the opportunity to explore African dragonflies. Although common species in Africa, they nevertheless filled me with joy and a sense of adventure upon seeing something new. I can now make a comparison on Singapore’s dragonflies and their relatives across the Indian Ocean.

Damselflies from the genus Pseudagrion come from a large widespread subfamily Pseudagioninae. We have four species here including a very rare one, Pseudagrion rubriceps (Orange-faced Sprite) which now seems to exist only at the pond in Toa Payoh Town Park.

I saw three relatives in Nairobi. One of them is Pseudagrion salisburyense (Salisbury Sprite) that has a range from interior South Africa to east, central and western Africa.

Pseudagrion massaicum (Masai Sprite) is an extremely beautiful damselfly. Males have red eyes, orangey thorax, green markings along the abdomen and blue abdomen tip. Surely one of the most colourful damselfly I’ve seen.

The last Pseudagrion species can’t be identified with certainty. Its either P. spernatum or P. kersteni.
Ceriagrion is another large genus but only two species are in Singapore. Ceriagion chaoi (Fiery Coraltail) in Singapore is very much like Ceriagrion glabrum (Common Citril) from Africa. Their colour scheme is very similar but C. chaoi has a brighter red abdomen and olive thorax.

Dragonflies of the genus Trithemis are from the subfamily Trithemistinae or commonly called Dropwings. There are more than 50 Trithemis species worldwide, and they are essentially African but five have made it to Asia. Singapore has three species. One example is Trithemis festiva (Indigo Dropwing). Here, this species is predominately stream loving and have adapted very well to large canals and storm drains.

In the UN compound, I observed four species, one more than the whole of Singapore. The four are: Trithemis arteriosa (Red-veined Dropwing), Trithemis cf. dorsalis (Dorsal Dropwing), Trithemis stictica (Jaunty Dropwing) and the prettiest of the lot Trithemis kirbyi (Kirby’s Dropwing).

The widespread genus Brachythemis is from the subfamily Sympetrinae. Singapore has one representative, Brachythemis contaminata (Common Amberwing). Wherever B. contaminata occurs, they are always in great numbers and have a habit of flying close to the ground especially the females and immature males.

In Africa, Brachythemis dragonflies are also known as Groundlings. One species from Nairobi is Brachythemis leucosticta (Banded Groundling). Males have banded wings while females have clear wings.

Probably the most common dragonfly genus in Singapore is Orthetrum (subfamily Libellulinae). We have five species, all of which can be easily seen. In Asia, some Orthetrum species have evolved reddish colour in mature males. However pruinosed blue in mature males is more common in the genus, for example our Orthetrum luzonicum (Slender Blue Skimmer).

African Orthetrum species are mostly pruinosed blue Skimmers thus making their identification much more difficult compared to in Singapore. I saw one species in Nairobi, Orthetrum julia (Julia Skimmer) where an immature male has greenish thoracic markings.

Aeshnids of the genus Anax are highly territorial. While in Nairobi, I spotted one big dragonfly speeding around a pond in a patrolling flight and immediately I knew it is an Anax. Very fortunately, it perched and I got a clear picture of this handsome Anax imperator (Blue Emperor). It is positively more colourful than Singapore’s Anax guttatus (Emperor). And a bonus, an ovipositing female was sighted the next day.

Aside from those highlighted here, I observed 15 species in total. It was great to see those African relatives. There’s much more to learn on dragonflies knowledge beyond Singapore. Furthermore through these sightings I got acquainted with Klaas-Douwe B. Dijkstra and Viola Clausnitzer. Both of them are experts in African dragonflies and very friendly in helping to confirm the species. Not forgetting Warwick and Michele Tarboton who generously sent me their guidebooks before I left for Kenya.

Hence local dragonfly lovers should take all opportunities to spot dragonflies beyond Singapore. Remember, there’s about 5700 species in the world!

Pictures taken at: Toa Payoh Town Park, January 2009; Venus Trail, September 2009; Nairobi Kenya, May 2010; Bishan Park, July 2010; Kranji Marsh, July 2010

References:

Silsby, J., 2001. Dragonflies of the World, CSIRO Publishing, Victoria, Australia.

Tarboton, W. R. & M. Tarboton, 2005. A Fieldguide to the Damselflies of South Africa. Privately published.

Tarboton, W. R. & M. Tarboton, 2009. South African Dragonflies. A Quick Guide. Graphic Touch Guides, South Africa

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.

Orthetrum chrysis ; Larva Emergence

Although dragonfly larvae have been studied widely, this aspect of their life history still harbours unsolved mysteries. For example, there’s several dragonfly genus whose larvae are still unknown and not found or described. The best way to study larvae ecology is to rear them ex-situ. This requires patience, time and acquired knowledge through practice. Inspired by the excellent work by Dr. Ian Choong from Malaysia and encouragement from Yeh Wen-Chi in Taiwan, I decided to take on this challenge whole heartedly.

Two to three days prior to emergence, a typical larva will stop feeding and climb partially out of the water. This is when aquatic respiration slowly change into atmospheric respiration. Once ready it will leave the watery environment into an aerial existence. After rearing this larva for 20 days, a miracle of nature finally unfolded.
Tropical dragonflies mostly emerge at night to pre-dawn. There are four stages of emergence. The first is when the larva search for a suitable support, climbing upwards and away from water. At this stage, the cuticle is still intact.

At second stage. the cuticle of the head and thorax split with the adult now pushing itself out of the moult (known as exuvia in dragonflies). Looking at the process, I actually sensed the dragonfly’s physical exertion. Slowly, the head, thorax and legs emerged with only the abdomen still inside the exuvia. Normally, a dragonfly would then rest for a while.
When it has regained energy, it swung forward to hang onto the exuvia and pulled its abdomen out. This is the third stage. The dragonfly is now fully emerged but looks all wriggled and fragile.

Finally in stage four, bodily fluids are pumped throughout the body to expand the abdomen and wings and also gaining full colour. Just like an ugly duckling, its wings open and transformed into a beautiful reddish female Orthetrum chrysis.
The entire four stages require 1-2 hours. Sacrificing sleep from 4-6am to witness this event is certainly worth it. For a dragonfly, it now enters an aerial lifestyle of hunting, territorial fights and procreating the next generation.

Orthetrum chrysis is a common dragonfly. Although mostly encountered at forest margins, we can also find them in well-vegetated park ponds. Of the several red-coloured dragonflies in Singapore, males of O. chrysis can be recognised by its red abdomen and blackish-brown thorax.

Pictures taken at: ex-situ, May 2009 (larva and emergence); Bishan Park pond, September 2008 (adult male).

References:

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

Silsby, J., 2001. Dragonflies of the World, CSIRO Publishing, Victoria, Australia.