The Small Pincertail is a relatively common & widespread species in the Iberian Peninsula, though apparently absent from the west coast regions of Portugal & the north coast regions of Spain.
There are three subspecies of Onychogomphus forcipatus with Onychogomphus forcipatus unguiculatus being the one that occurs throughout the Iberian Peninsula. It is a predominantly black & yellow, medium size dragonfly, with blue eyes in the Mediterranean area, (though greenish eyes further north in Europe). It is very similar in appearance to the Large Pincertail - Onychogomphus uncatus and the two species cannot be reliably separated by colour markings alone.
For instance the black stripes on the upper surface of the thorax are usually connected via the black central keel in the Small Pincertail, whereas the Large Pincertail there is a gap between the two, sadly however that is not always the case!
The anal triangle on the hind wings of a male also offers a method of separating the two species, usually comprising of 3 cells in the Small Pincertail (see photo) and 4 cells in the Large Pincertail.
However the male anal appendages offer a more reliable feature to separate the two species with the Small Pincertail having a subterminal knob on the inferior anal appendage (see photo). This feature can only really be seen clearly by examining the insect in the hand, or perhaps a little more easily, by taking a digital photo, concentrating on a side view of the anal appendage and enlarging it on the camera's LCD screen.
The Small Pincertail frequently occurs along rivers & streams, often with very shallow water, peppered with large boulders & rocks from where mature males sit with their claspers raised defending small transient territories perhaps 2.5 to 3 metres apart.
Scientific name: Onychogomphus forcipatus (Linnaeus, 1758)
English common name: Small Pincertail
Total length: 46 to 50mm
Hind Wing length: 25 to 31mm
Flight period in Iberia: May to mid September
Habitat: Usually rivers & streams with regularly protruding rocks or boulders, occasionally larger still water bodies.
Distribution: Europe (except Britain), North Africa & the Near East. Widely distributed throughout the Iberian Peninsula, though apparently absent from the coastal fringes of Galicia, Asturias & Cantabria. Similar species: Very similar to the Large Pincertail - Onychogomphus uncatus which contrary to it’s name is only marginally bigger than the Small Pincertail.
This article first appeared on the Wildside Holidays website at: http://www.wildsideholidays.com/natural/insects-and-creepy-crawlies/97-dragonflies/320-small-pincertail-onychogomphus-forcipatus-.html