Onychogomphus costae
Onychogomphus costae Selys, 1885
Local names: Faded pincertail, Plain hook-tailed dragonfly, Costa's pincertail, Braune Zangenlibelle, Moorse tanglibel
Species Information
Description
Small and inconspicuous species with a peculiar colouration; ivory-white, ochre, brown beige and the almost total absence of black markings. Easily overlooked owing to its small size and camouflaging colouring. Its size and colour make it easily distinguishable from the other pincertails. Also it is the only Onychogomphus in its distribution range with a light-coloured pterostigma. The terminal appendages of the males are quite particular as well; the lower one is slender, free of teeth and much shorter than the upper ones. The males also have a tuft of long whitish hair on the lower part of S7, which are 3-4 times as long as any hair on S6.
Resembles Paragomphus genei in size, posture, pale pterostigma and indistinct markings, but the latter has green face and thorax, more abdominal black and broad flaps on S8-S9 in the males. Appendages also differ.
Size
Habitat
Onychogomphus costae is found in running waters in arid and semi-arid environments. In Europe it is restricted to the driest lowland areas. The running water habitats in such habitats are challenging for the aquatic fauna as they are often intermittent in summer but can be torrential during the rainy season. Onychogomphus costae seems to be well adapted to this and is sometimes observed at residual pools in largely dry river beds. It seems more resistant to sudden fluxes in water flow than other species of dragonfly. In the Maghreb it is often the only dragonfly present, although at low densities, along permanent river systems with seasonal catastrophic discharge. The species is tolerant of naturally brackish rivers with a salinity ranging from 4 to 7.9%.
Distribution
onychogomphus costae is restricted to the West Mediterranean and is found in the Iberian Peninsula and the Maghreb. On the Iberian Peninsula it is found in the south and east, reaching north to the foothills of the Pyrenean and the Cantabrian mountains along the Ebro valley. The species is very rare in Portugal and absent from the whole north-west of the peninsula, probably due to the colder and more humid climate. It is relatively rare and localised within its European range when compared to the Maghreb. Information on the size and extent of the European populations is very limited.
Flight Period
May to August
Behavior
Poorly known, has been noted to rest on bare ground.
Conservation Status
Similar Species
Paragomphus genei
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.