Monday, 16 September 2013

Macrogomphus revisited

Martin Schorr was kind enough to send the Foerster article, so I could check the description of M. rivularis. The description has some interesting points. The anal triangle is not mentioned, but Chao says that M. guilinensis has 4 cells in the triangle. The specimen has only 3. The description of Foerster mentions that the yellow line over the frons is constricted from the backside, a feature absent in the drawings of M. guilinensis, but shown by the female specimen. Moreover, the drawings of M. guilinensis show an oval spot on the vertex, the female specimen has only a line, as described by Foerster. On the other hand, Foerster says the width of segment 8 at the rear edge is 3 mm and at the rear of segment 9 2 mm. The photos of the male show that the width of S8 is twice that of S9. Chao does not mention the width ratios. Then there is the issue of the relative length of S7-9. Foerster gives 5.5/4/7 for rivularis, Chao 7.5/4.5/11 for guilinensis. The male specimen is approximately 5.5/4/8.5 and the female 5/4/8.5, both closer to rivularis, but not the same, especially evident in the female, although that was not described by Foerster. It is all little to go by and I cannot even by sure that M. rivularis is not the same species as M. guilinensis. Chao does not mention differences between M. rivularis and M. guilinensis, although he does mention identifying characteristics in relation to M. matsuki, M. borikhanensis and M. annulatus. Anybody any suggestions?

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