Dragonflies & damselflies of Thailand: 40. Prodasineura autumnulis (Fraser, 1922)

No: 40 / Family: Platycnemididae / Genus: Prodasineura

Name: Prodasineura autumnulis / Black Threadtail

Habitat: Forested streams
Province(s): Widespread
In flight: Year-round / Sightings (by me): Very common

Easily confused with: Prodasineura humeralis

When I first visited the River Chi, Khon Kaen back in early 2008, I spotted my first ever Prodasineura species - Prodasineura autumnulis. I took a number of photographs of both the male and female. In this area they are in small numbers, but you often see one or two there. For over a year, I thought that the sub-adult male was fully grown. It wasn't until I went to another place south of Nakhon Sawan that I noticed the adult males are jet black. At first I thought it was a different species, but research proved otherwise.

The Male

The adult male is black on the thorax and abdomen and also becomes slightly pruinosed with age. It is easily frightened and quite hard to photograph. This is the most common stage.

As the male ages, it changes slightly. This specimen, I captured in Nakhorn Nayok, has slight pruinescence to the side of the thorax (photo 28/03/2011 - added 02/04/2011) ...

... and this one is completely pruinosed save a small greenish-bronze? part of the thorax. I must admit, this is the only specimen I have seen like this. It was at a largish waterfall in Lomsak province, Petchabun (14/07/12). Though it looks right, it acted differently to all the others around it and the colours add to the mystery. Maybe, just maybe, it may be a slightly different form. Can anyone shed light on this?

The Female

The female is almost identical to the sub-adult male, but the abdomen is far more robust. Like the sub-adult male, it tends to hide away and is less commonly seen.