Species: Coeliccia didyma
Common name(s): Twin-spotted Sylvan
Habitat: Shaded, forested streams (uplands & lowlands)
Province(s) sighted: Kaeng Krachan NP; Nam Nao NP (Petchabun); widespread (Chiang Mai); Phu Rua NP (Loei); Khao Yai NP (Nakhorn Ratchasima); Kanchanaburi.
Sightings (for me): Common
In flight (that I know of): April-October
Species easily confused with: Coeliccia sp.
Coeliccia is one of my favourite genus of damselflies and Coeliccia didyma is the one I have spotted the most. There are twelve known Coeliccia species in Thailand and I have now spotted six, so I am half way there! C. didyma likes very shady forested areas along slow moving rivers and streams.
The male is far more common than the female and is easily recognisable with its blue markings / stripes on the thorax and the end segments and caudal appendages are also blue.
Male with a difference...
This male has tiny additional markings on the thorax. According to Noppadon, there can be minor differences in population, even in the same population. So don't start jumping for joy thinking you've just discovered a new sub-species (like I did).
The young male
The male differs in appearance as it ages. Below is a sub-adult male. You can see the markings on the thorax are slightly different than those of the adult and the colour is also different.
An even younger male...
This very young male is similar to the one above, but hasn't yet developed any of the blue colouration differs in appearance as it ages. Below is a sub-adult male. It also has the same markings as the one above.
I haven't seen too many female C. didyma, but I was lucky to spot two females at Nam Nao National Park. The specimen below is an adult female. It is very similar to many other female Coeliccia species but the markings on the end segments are distinct. Younger females are yellow instead of blue.
The young female
I have spotted C. didyma at a number of places throughout the year. The best place I have seen them was Nam Nao National Park, mainly because there are 4 species of Coeliccia that reside there, including C. didyma, C. chromothorax, C. poungyi and a species very similar to that of C. loogali.