Saturday, 23 April 2016

Sarasaeschna minuta - superb addition to the Vietnamese list

 I was very excited when I bumped into a hovering Sarasaeschna species on April 17 at a stream near Tuyen Lam Lake near Da Lat in South Vietnam. I missed when I tried to catch it, but later caught another specimen and still later a second. Indeed, a small Sarasaeschna species. My fifth species of the genus for Vietnam.

Checking against Asahina's description of Sarasaeschna minuta it matched very well. He described Sarasaeschna minuta in 1986 from a specimen collected in north-east Thailand. As far as I know this is the only record and it is thus also known from only one location. This is therefore a very exciting discovery. The original record was from 1000asl, the current locality about 1350asl.

In fact there are two discrepancies. The first it that the superior appendages have a ventral tooth at the start of the broader section, which is not evident from Asahina's drawings. But otherwise the shape of the appendages is just too good. Also, Asahina described the abdomen as 30mm and HW 28mm. My specimen has HW 28mm, but the abdomen is 36mm. It would need verification against his type specimen, but I think the description may be faulty on this point.

Male Sarasaeschna minuta in hand
Scan of the same male

Appendages in ventral view. Note the long epiproct, which is incised apically in a horse shoe shape

Here in dorsal view you can see that the broader section of the superiors starts with a tooth

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