As if Gomphus weren’t a strange enough name, now we’ve got Onychogomphus. These are good-looking medium-sized dragonflies with the most fearsome-looking anal appendages – on the males, anyway.
These are rather difficult to identify by description, especially to separate from O. uncatus. The vernacular names don’t help much: Small vs. Large Pincertail is no use in isolation and eye colour is apparently not consistent enough for Green/Blue-eyed to be reliable. Detailed diagrams tend to be necessary and there are some very good ones here. It’s also worth checking out dragonflypix.com.
Just to make things even more fun, O. forcipatus has a couple of subspecies. In France, there’s O. f. forcipatus and O. f. unguiculatus, the so-called subterminal knob (see Dijkstra/Lewington) on the male’s lower anal appendage being one of the main distinguishing features. Fortunately, there are few areas where both subspecies coexist (see Grand/Boudot). A combination of physical features and location makes me reasonably confident about my classification below.
Our first Onychogomphus forcipatus encounter was at the wonderful Pinail Trail in a less-than-wonderful year, 2011; many pools were all but dried up after a long, hot spring. We saw one again near the Pinail in 2012, together with one at the even more superb Tourbières de Vendoire. These would be O. f. forcipatus. Our latest is O. f. unguiculatus at Montesquieu des Albères in 2014.
- blue-green eyes, greener in the north
- often a yellow bar on th evertex between frons and occiput
- the yellow anterior ridge of the thorax divided by a black line along the mid-dorsal keel
- see diagrams referred to above for the antehumeral stripe shapes
- ♂ – fearsome hooked appendages (the pincers), the lower one with a subterminal knob
- normally 3-celled anal triangle
|O. f. forcipatus|
|O. f. unguiculatus|