Onychogomphus uncatus
Onychogomphus uncatus (Charpentier, 1840)
Local names: Large pincertail, Große Zangenlibelle, Grote tanglibel, Gomphe à crochets
Species Information
Description
Yellow and black pincertail similar to Onychogomphus forcipatus. Eyes are light blue in females and blue-green or green in males. The males are easily recognised by the appendages that are shaped like pincers.
O. forcipatus and O. uncatus is best distinguished as follows:
- The vertex of O. forcipatus is not all black. There is a yellow bar between the frons and occiput. However, this is sometimes unclear.
- The lower appendage on males bears a subterminal knob in O. forcipatus but not in O. uncatus.
- On O. uncatus, The 'collar' (the transverse yellow area on the anterior ridge of the thorax) is severed by the black area along the mid-dorsal keel.
- On O. uncatus, The yellow antehumeral stripe dorsally connects with the broader yellow stripe before it. Thus the black stripe separating them is not connected with the black along the mid-dorsal keel.
- The black on the side of the thorax is more extensive on O. uncatus; the stripes are not broken, but often partly confluent. Especially in southern O. forcipatus these stripes are reduced.
- On females the distinctive character is the absence of two small yellow tubercles behind the eyes on O. uncatus
Size
Habitat
Onychogomphus uncatus tolearates higher water velocity than O. forcipatus, and is more frequently found in fast-flowing stony streams and rivers than the latter, with a preference for partially shaded habitats. It is common in rapid headwaters in hilly and mountainous landscapes usually up to 800 m, locally up to 1 300 m in Europe and 2 340 m in Morocco, but it also often occurs in large slow-flowing, lowland rivers in the west of its range.
Distribution
Onychogomphus uncatus is endemic to the Western Mediterranean. In north Africa it is found in the hills and mountains of northern Morocco, Algeria and Tunisia. The main range in Europe is from the south-western half of France west to the Iberian Peninsula and east to Italy. It is absent from the Mediterranean islands with the exception of Sicily. The highest density of populations is found in the south-west of France and parts of the Iberian Peninsula, and in these areas the species is generally common. It has a scattered distribution in the Iberian Peninsula, being regionally absent in the driest parts. It is relatively uncommon in Italy, with populations confined to areas in the north and the western half of the country.
Flight Period
May to September
Conservation Status
Similar Species
Onychogomphus forcipatus
External Links
Genus: Onychogomphus
Onychogomphus is a genus of dragonflies in the family Gomphidae. They are commonly known as Pincertails.
Identification
These dragonflies are best known for the male's large appendages. The upper and lower appendages are both distinctly longer than S10 and are curved strongly inwards, like pincers. All species, except O. costae, have a yellow abdomen ringed with black markings, and a yellow thorax with black stripes O. costae is more brown and less distinctly marked. The hindwing has a small anal loop consisting of 1-3 cells. Therefore there is not a straight perpendicular vein running directly to the wing's hind margin from the last thick lengthwise vein in the wing base.
Separation from other genera
The males can hardly be misidentified because of their conspicuous appendages, but females are less obvious. They may be mistaken for Gomphus, Ophiogomphus or Paragomphus. Only Ophiogomphus also has an anal loop, but in this genus the thorax is largely green and the female has two crests on top of the occiput. Paragomphus species are smaller. The male has broad flaps on S8-9 and the female has a row of small black denticles on the rear of the occiput. Gomphus is marked differently, the abdomen generally blacker and is lenghtwise striped, rather than ringed.
Family: Gomphidae
The Gomphidae are a family of dragonflies commonly referred to as clubtails or club-tailed dragonflies. The family contains about 90 genera and 900 species found across Europe, Asia, North and South America and Australia. The name refers to the club-like widening of the end of the abdomen (S7-S9). However, this club is usually less pronounced in females and is entirely absent in some species.
Characteristics
Clubtails have small, widely separated compound eyes, a trait they share with the Petaluridae and with damselflies. The eyes are blue, turquoise, or green. The thorax in most species is pale with dark stripes, and the pattern of the stripes is often diagnostic. They lack the bright metallic colors of many dragonfly groups and are mostly cryptically colored to avoid detection and little difference between the sexes is seen. Adults are usually from 40 to 70 mm in length.
Clubtails are fast-flying dragonflies with short flight seasons. They spend much time at rest, perching in a suitable position to dart forth to prey on flying insects. They tend to perch on the ground or on leaves with the abdomen sloping up and its tip curling down a little. Larger species may perch with a drooping abdomen or lie flat on a leaf. Another stance adopted by clubtails perching in the open is obelisking, standing with the abdomen raised vertically, a posture adopted otherwise only by the skimmers.
Most clubtails breed in streams, rivers, or lakes. The nymphs are unusual in having a flat mentum, part of the mouthparts, and their antennae have only four segments. They burrow in the sediment at the bottom of the water body.