Sunday, 24 January 2016

My third Vestalaria species in Vietnam: V. vinnula

In September last year I visited the mountains west of Da Nang close to the Laotian border and one of the objectives was Vestalaria vinnula, which had been recorded there by Toan previously. Interestingly on the stream where it was supposed to occur I found the very similarly looking V. miao. This is not to say that V. vinnula there had been a misidentification. I have seen the specimens and the identity is beyond doubt. Apparently in a different season a different Vestalaria inhabits the same stream. Very interesting. But I was of course also disappointed.

But when in December we visited Lam Dong Province near Da Lat one of the few damselfly species around was in fact Vestalaria vinnula (co-occurring there with similar looking Mnais mneme, a species that has pterostigmata and thus is easily separated from Vestalaria species upon a closer look). Here a few photos from V. vinnula. This species has longer inferior appendages, unlike V. miao, in which the inferiors are very much reduced. The shape of both the superiors and inferiors is much like those of V. smaragdina from the northern mountains and difficult to separate on the basis of these even on close inspection, but unlike V. smaragdina and very much like V. miao, V. vinnula has darkened crescents along the wingtips. The combination of long inferiors and dark crescents help easily establish its identity.

V. vinnula was described from the Lam Dong Province and subsequently also found further north, near Nha Trang, and, as indicated above, also occurs west of Da Nang. Given its widespread occurrence and the close proximity of some of the locations where it has been seen to the Lao PDR, it is probably not endemic to Vietnam. Apparently is survives well into December and it is thus conceivable it can be observed year round.

Vestalaria vinnula male. Note the darkened crescents on the wing apex and the in this photo just visible obvious lower appendage.
Appendages in lateral view. In this way it cannot be separated from V. smaragdina (on ventral or dorsal view it can, but not with ease), but the combination with the wing pattern helps clinch the ID.
Another male, this specimen with some pruinosity on the ventral side, very much like hyaline-winged Mnais mneme, which lacks the dark crescents and has dark pterostigmata.

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