Monday, 6 October 2014

Planaeschna cf.(not quite) tomokunii - a great find at Pia Oac*

*Subsequently (October 18) a male was caught and it appears to be P. tomokunii after all.

After the splendid male Planaeschna gressitti at the pass of Pia Oac, we saw another Planaeschnid at the gold digger stream, where it was hunting above the stream in a dark corner under a rock and tree near a rapid. Netted it turned out to be a female. A slight disappointment, but I carried it home anyway. It was very small with a total length of only 63mm, small for the genus. But it also had some interesting characteristics. It had for instance quite a bland face, without clear bright and dark patterning. It also had very reduced abdominal markings on S4-7, with only a pair of medio-dorsal markings, but nothing anterior or posterior. These markings were also unconnected to the ventral spots. S8 had only a small yellow ventral anterior spot and S9-10 were all dark. On the other hand, S2 was completely yellow in the ventral half, and S1 largely so (but dark on the dorsum). The ventral projection of S10 is spine rich, in the words of Sasamoto et al. (2013).

This species is very close to Planaeschna tomokunii (Asahina 1996 and Sasamoto et al 2013) in general appearance, for instance the facial pattern, the pattern of the abdomen and thorax, and the spine rich projection. There are however several differences as follows: 1) S1 is not all yellowish, but has dark dorsum, 2) The medio-dorsal markings on S2-4 are not connected to the ventral spots, the nodal index is rather different (which may be due to the smaller size) but is 15-22/22-16:19-16/16-18 whereas in Sasamoto et al. it is given as 21-24/27-21:24-19/19-21, 4) the anal loop is 7-celled versus 11-celled in Sasamoto et al for P. tomokunii and 5) the FW triangle is 3-celled, against HW 4-celled, which is strange in the genus where normally the FW has more cells than HW. In sasamoto et al it is FW 5-celled against HW 4-celled. The overall size of only 63mm against 72mm for P. tomokunii could be an aberration, something that also explains the differences in number of cells, but the additional differences in color pattern and the fact that the FW triangle number of cells is smaller than that of the HW makes me want to postulate this is in fact a different species, albeit similar. All other Vietnamese Planeaschnids can be excluded and I have not been able to find a Chinese species of similar appearance.

The female Planaeschnid cf. (not quite) tomokunii. Note the reduced abdominal markings, with even on S2-3 the medio-dorsal spots unconnected to the ventral markings

In dorsal view, showing the distinct Planaeschnid venation

The rather plain facial pattern, very good for P. tomokunii

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