185: Aciagrion occidentale Laidlaw, 1919

Number: 185 / Family: Coenagrionidae / Genus: Aciagrion   

Species: Aciagrion occidentale / Green-striped Slender Dartlet  

Habitat: Well-vegetated Ponds   

Province(s) sighted: Chaiyaphum

In flight: October / Sightings (by me): Rare

Species easily confused with: All Aciagrion species

Tiny, blue and all look the same! Talk to any dragonfly lover about Aciagrion and they instantly wince. It is an incredibly difficult and confusing genus that needs to be resolved - though anyone who dares to do it is a brave individual indeed. There are several known species in Thailand, though one or two of them could have been misidentified (possibly even by the original authors). That said, it seems that there are possibly several more out there that are yet to be described. One of which, I may have spotted last week. It is an Aciagrion species that seems to fall between A. hisopa and A. borneense with a sprinkling of A. pallidum thrown in for good measure. Superficially, it looks like A. borneense. However, the striking difference is the solid blue patch on the abdomen (save a tiny "v" nick) and the appendages are white. The colouration of the rest of the male seems to match that of A. borneense. 

Since posting this, and after a lot of hard work by a number of ode experts, it seems that there is a little light at the end of the Aciagrion tunnel of mess. Most species in Thailand, at least, can now be identified through different characteristics. And it turns out that this is, indeed Aciagrion occidentale. Commonly known as the Green-striped Slender Dartlet. I thought I had seen this on numerous occasions but no. However, this one I saw in October at Phu Khieo Wildlife Sanctuary in Chaiyaphum is correct. Yaay! I am very happy indeed. Furthermore, looking at iNat, someone has found it in Khon Kaen (where I live), so I will be looking for the female there this September onwards - it's a late season specialist.

The Male

Looks similar to all male Aciagrion species. However, the tiny 'V' nick is the giveaway, along with the white appendages. The nick or groove is variable and can be much larger.

Here is another I found, I think...