Brachygonia oculata male is a small, very spectacular dragonfly, which we have encountered several times, always at the edge of swampy forests or peat bogs in the forest, for mature males.
It is impossible to confuse it with another species because of the bright white spot on the dorsal side of its abdomen.
It has large eyes and measures only 21 to 24 mm (1).
Below, the individual on the right is probably young, with a thorax even more white than yellow and largely green eyes capped with red.
Its habitat is limited to the forest or its immediate surroundings, in peat bogs, marshy areas, or even along sluggish streams with bottoms covered with debris and leaves.
It is noted that the white pruinosity extends precisely on the dorsal face of segments 3, 4 and 5. However, Kirby, who created the genus Brachygonia (2) and takes Brauer’s Tetrathemis oculata as his type, writes: « In all the specimens of the male the abdominal segments 2 (behind the carina), 3, and 4 to the middle are dusted with pale blue. On all the specimens of males, the abdominal segments 2 (behind the carina), 3 and 4 to the middle, are powdered with pale blue. » Probably a
calami slip , because Kirby, we can trust him, knew the anatomy of odonates very well !
The females, above, have no pruinosity on the abdomen and are much less spectacular. We find roughly the same coloration on the thorax, but the eyes are quite bright red above, green below, like the young male shown above.
The photo below is typical of what happens with these dragonflies that live in the forest, in the shade; all the photos are taken with flash and to adjust the lighting, the flash emits a micro flash that allows the sensor to measure how powerful the main flash will have to be to correctly expose the scene. Many forest dragonflies are sensitive to this first flash and take off very briefly, the main flash that follows the first by a few milliseconds finds them in flight. If we repeat the shot, the dragonfly can take off and rest 4, 5, 6, 10 times… and all the photos are usually blurred. Most often, the dragonflies get used to it and end up staying quiet.
We are often only a few dozen centimeters away and I have always wondered how they manage to fly properly after such repeated glare!
The species is found from southern Thailand, through the Malaysian Peninsula, to Borneo (Sarawak, Brunei, Sabah and Kalimantan) and Sumatra.
IUCN Red List.
Etymology
Brachygonia (Kirby, 1889) from the Greek brachy , for short, and the ancient Greek gonia for generation (from which we made gonad ) certainly related to the secondary genital apparatus not very prominent under the second segment. Kirby writes: » appendages of the second segment distinct, not very prominent. « .
Oculata ; I have not managed to find the original description by Brauer, where he describes the species under the name Tetrathemis oculata. Oculatus, in Latin, means provided or endowed with an eye or eyes, no doubt to emphasize the oversized eyes of this species.
The Anglo-Saxons simply call it Pixie ( goblin ). And, I discover with this species, the Malaysians have defined Malay names for the species that populate their territory (3); that of our species is Penyiring Dewi Oren. I should also mention that there are only 9 entries on a popular search engine for this name.
1- Robin Ngiam & Marcus Ng – A photographic guide to the Dragonflies and D.f Singapore – John Beaufoy Publishing – 2022.
2- W. F. Kirby, 1889 – A Revision of the Subfamily Libellulinae, with Descriptions of New Genera and Species. Transactions of The Zoological Society of London, in 1889, in volume 12, pages 249-348. P. 310.
3- Checklist Odonata: Scientific, English, and Malay Names.