Sunday, January 15, 2012

Agriocnemis minima

Agriocnemis minima - first record of this species in Singapore! This tiny damselfly hasn't been spotted in Singapore (nor Peninsular Malaysia, if I'm not mistaken) before.

At the survey sites is at Chestnut Marsh, and on our second survey there we found a female individual which did not look like the more common A. femina. Upon checking with experts in the field we were not able to do a proper identification due to extreme similarity in colouration between several species, and also the individuals of this genus tend to have a huge range of different colour forms. Female Odonata individuals is generally hard to differentiate to a species level if there is no good documentation or clear differences in the appendages.

On a survey yesterday morning we found two males and a female after much time spent searching and tracking, because these damsels are really small! (even for damselflies) Also, they tend to perch on the base parts of the reed, near the water surface, thus its easy to miss them if you just do a quick glance.

 We're now able to identify it as the Agriocnemis minima because the male appendages for this genus are rather different for each species. It can be differentiated from the other Agriocnemis species by the structure at the end of its appendage - the A. minima has a hook-like structure, which can be seen in this photo.

For more info: and you can see that the other forms are really different! The female colouration tends to be duller, but this little guy has really brilliant markings :)

Tuesday, January 10, 2012

Amphicnemis gracilis / bebar

At a recent survey in the Central Catchment Reserves we had a pretty good haul!

Species found:
Vetalis amethystina
Amphicnemis bebar
Libellago aurantiaca
Prodasineura notostigma
Euphaea impars
Coeliccia octogesima
Prodasineura collaris
Libellago hyalina
Drepanosticta quadrata
Orthetrum chrysis
Orchithemis pulcherrima

We had our first sighting of the Libellago hyalina in that area! It is quite commonly found at the upstream segments of the same stream system but we have never seen it along this particular trail, although it is frequented by the L. aurantiaca.

An interesting find would be the Amphicnemis bebar. Only recently described, it is completely similar to the A. gracilis on the outside. The only viable way of differentiating the two on the field is to consider the appendages as follows:

The left is the bebar, the right gracilis.

The habitat in which they reside are slightly different as well. Prof Murphy has a specimen of A. bebar collected years ago, before its description, mislabelled as A. gracilis. With this proof that Singapore had this species before, it was soon rediscovered again in the Central Catchment Reserves.

Both species have various colour forms - a green/black thorax, black abdomen form and a red thorax, black abdomen form. The red form is pretty striking! We recently saw both forms of the A. gracilis at another survey in the Petaling stream system.