Sunday, February 27, 2011

22. Aciagrion pallidum (Selys, 1891)

Number: 22
Family: Coenagrionidae
Genus: Aciagrion
Species: Aciagrion pallidum
Common name(s): N/A
Thai name(s): แมลงปอเข็มเรียวสามสี
Habitat: Widespread - edge of forested uplands streams to exposed lowland lakes
Province(s) sighted: Widespread (Khon Kaen); Nam Nao NP (Petchabun); Khao Yai NP (Nakhorn Ratchasima); Khao Soi Dao NP (Chantaburi); Widespread (Chiang Mai); Pang Sida NP (Sa Kaew); Mukdahan NP (Mukdahan).
Sightings (by me): Very common and widespread
In flight (that I have seen): February-January (though commonest in the cool season)
Species easily confused with: None

A common winter species (even though it's still about 8 million degrees) is Aciagrion pallidum. It can be seen throughout Thailand and I have seen specimens pretty much in every corner - both lowlands and uplands. They tend to prefer flowing water, but I have seen them near lakes with no river for a good distance. 
According to Noppadon, even this species is split into two sub-species and should be up for revision. However, until that time I will refer all sightings as one. This really is a tough genus!

The male
The male changes slightly as it matures. The end segments change from white to orange (unless I've got it the wrong way round). I have also spotted males in Chiang Mai with blue end segments... Noppadon Makbun seems to think this could be a new sub-species. Let's hope!

The mature male
As above, but now boasts dashingly handsome orange end segments.

The female
The female is almost identical to the younger male, but the abdomen is more robust.

This one I saw ay Nam Nao recently has a blacked ovipositor. Has it just been ovipositing?

Mature female ...
This older female has a metallic purple/pink sheen to its thorax.

The 'other' A. pallidum
As noticed by Noppadon Makbun, there is, what seems to be, a different form of this species. The male is distictly blue and the female is also blueish with a more reddish abdomen. As of now it is simply A. pallidum. Hopefully, one day, someone will revise this species.

The 'blue' male (though not the best shot in the world)

... and the 'blue' female (though its abdomen is distinctly reddish)

The copula
I saw my first ever copula recently at Phu Wiang NP, Khon Kaen and ironically it turned out to be the 'blue' variety - the first and only time I have seen it in Khon Kaen. 

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