Tyriobapta torrida

Females of different dragonfly species have different ovipositing modes. Scientists classify the different modes into three broad categories: endophytic (oviposition inside plants), exophytic (oviposition on anything except plants, which is water or substrate) and epiphytic (ovipositing on plants).

I’ve seen females ovipositing several times while out in the field. The most recent encounter gave me a chance to record videos of a particular female ovipositing in ultra speed mode.

This is the female of Tyriobapta torrida. She was flying in a circular motion at high speed and using the trajectory force to project water droplets and her eggs onto the water edge. Its amazing how fast she was flying and I can only imagine the aerodynamics involved. The lift and drag forces must be rather intense as well as the wings locomotion in overdrive to maintain the flight pattern. Not only that, she was going at it for almost 7-8 minutes. This is a lot of energy expended to produce the next generation. If only I can view this video in slow motion, which will certainly give an insight into the flight mechanics.

All the while, the mate-guarding male was hovering nearby. T. torrida males are easily recognised by the dark iridescent patch on the hind wing base. This species is rather common in our forests. T. torrida is the largest species within its genus. Where they occur, they are usually abundant with several individuals occupying and disputing small territories. Sexual activities are known to peak at around noon.

Corbet’s book described females from some other species diving underwater and ovipositing while submerged. Some species have been recorded to descend down to 1m depth. Now that is really a sight I want to behold.

This post is dedicated to Professor Philip Corbet who passed away on 13th February 2008 aged 78.


Pictures and videos taken at: Western Singapore, October 2007 & Venus Trail, March 2008.

References:

Corbet, P. S., 2004. Dragonflies: Behaviour and Ecology of Odonata. 2nd edition, Harley Books, Colchester.

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

Robber Fly

I was on Petai Trail recently and chanced upon this weird insect perching on a twig. It was motionless and thus perfect for a macro shot. It is about half the size of a palm and at first sight, looked rather fragile with its long abdomen hanging in mid-air. The poor insect seemed to be hanging for dear life.

It was only after I took a closer look at the picture and identification by Yixiong that I realised I’ve caught a glimpse of a fearsome predator of the insect world.

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.

Taxonomic classification aside, it is the ecology of robber flies that’s really fascinating. They prey on all sorts of insects, from easy ones like butterflies to prey that can put up a good fight like wasps, bees, spiders and dragonflies. In fact, some species are specialist hunters who target specific prey. Upon successful capture, a robber fly will inject its prey with saliva containing neurotoxin and other enzymes which immobilise the prey and liquify the tissue. Thereafter, the robber fly will suck on the soupy meal.

Not sure how well robber flies are studied in Singapore. But unsurprisingly, there’s tons of information on the web. This website http://www.geller-grimm.de/general.htm is one of the more comprehensive.

Pictures taken at: Petai Trail, March 2008.

References:

Geller-Grimm, F., T. Dikow & R. J. Lavigne. Robber Flies (Asilidae).
http://www.geller-grimm.de/asilidae.htm

Voluta nobilis

The second episode of Once Upon A Tree: Tides and Coastlines brought us back to nostalgic Singapore. Those were the days when people live much of their lives connected to the sea, for work as well as for play.

Work because, for example, The Raffles Hotel once stood just by the beach and would even be flooded during times of extreme high tides. Play, because trips to the sea then mean clear water, good fishing and excellent exploring on the seashore. The elders interviewed on the show mentioned big corals, huge fishes and dolphins were a regular sight. I’m quite sure one of the creatures they would have seen often too is this magnificent seashell, Voluta nobilis.

Voluta nobilis or “kilah” in the local language was once very common. They are now rarely encountered but still exists, mainly on our offshore islands. This pretty individual was spotted at Pulau Semakau recently. It’s been a while since I saw a live one, most of the time I found them as empty shells inhabited by hermit crabs. This individual’s siphon was fully extended as it searched for prey like bivalves. It will use its huge foot to suffocate and force its prey to open their shelves for oxygen. Once that occur, then its mealtime for V. nobilis.

Perhaps the elders from the documentary would be glad to know “kilah” can still be found in our waters.


Pictures and videos taken at: Pulau Semakau, February 2008.


References:

Tan, K. S. & L. M. Chou, 2000. A Guide to Common Seashells of Singapore. Singapore Science Centre, Singapore

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