Monday, 14 October 2013

Three grayish Orthetrum species from Vietnam

As described previously, up to know I found 6 species of Orthetrum in Vietnam. The blue gray ones gave me a little headache right in the beginning, but soon pattern started to evolve in the mist. The most robust and contrastingly coloured one is Orthetrum triangulare triangulare, with almost blackish thorax and head, S1-2 also blackish, S3-6 light grayish, S7 somewhat intermediate, S8-10 and appendages blackish again. This is a common dragonfly of muddy pools in forested environments. The second one is blue gray pruinose O. glaucum, a common species of small and somewhat larger shallow streams. A strikingly patterned insect when young, they soon become completely pruinose. Still easily separated from the next species, because their faces are dark. The last species is Orthetrum luzonicum. Males are somewhat more slender than O. glaucum and a shade lighter blue grey, but easiest separated due to their whitish faces and greenish blue eyes. Immatures are just like O. glaucum more strikingly patterned with stripes on the thorax. All have basal patches to the wings, dark brown in O. triangulare, brown in O. glaucum and amber in O. luzonicum.

Orthetrum glaucum, male

Orthetrum glaucum, male, note dark face

Immature male of O. glaucum

Orthetrum luzonicum, male. You can just about see the light face. The lighter eyes are another easy ID feature.

Copula of younger luzonicum, showing partial thorax pattern

Orthetrum triangulare triangulare, male, much darker than the other two

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