Gomphus graslinii
Gomphus graslinii Rambur, 1842
Local names: Pronged clubtail, Französische Keiljungfer, Gevorkte rombout, Gomphe de Graslin
Species Information
Description
A bright yellow and black clubtail with such characteristically forked male upper appendages that it can be identified by this feature without capture. The terminal part of the abdomen is less clubbed than of the other species of Gomphus, S8-S9 is only slightly expanded. Eyes are light blue. The antehumeral stripes are pale and narrower than the adjacent black bands, in particular the adjacent inner black band is quite wide and often connected dorsally with the black pattern on the thorax. This configuration recalls that of G. vulgatissimus. In G. simillimus the antehumeral and it's flanking stripes are alla bout equally thick, and the anterior one is dorsally unconnected.
All the segments of the upper side of the abdomen are longitudinally crossed by a yellow line. Distinctive in the males is the yellow marking in the form of a goblet on S9. G. vulgatissimus is all black dorsally on S9. In G. simillimus the posterior border of s) is black, although sometimes the central yellow marking reaches it.
Legs are black with yellow stripes on the femurs. Tibiae often entirely black. G. simillimus har yellow stripes also on the tibiae. G. vulgatissimus typically has all-black legs.
Size
Habitat
Gomphus graslinii favours slow-flowing parts of large streams and rivers surrounded by low forests and bushes, but can also be found along small permanent streams. Larvae favours sandy stretches covered with organic detritus. Several strong populations are known from hydroelectric dams on the rivers of the Massif central in France, however recently these were found to have strongly decreased probably due to the high amounts of accumulated sediments. The species is found up to 300-400 m in France and has been found up to 1 000 m in Spain.
Distribution
Gomphus graslinii is endemic to the south-west Europe. Most of the populations are found in two areas, one in south-west France and the other in the western Iberian Peninsula. In France this species is common only in an area extending from the lower Rhône River through the southern part of the Massif Central to the Charente-Maritime department. Here large populations are found in the rivers and tributaries of the Hérault, Tarn and Lot. This species is rare in other areas in France and has become extinct in some regions. It is very rare in most of the Iberian Peninsula but is reasonably widespread in the west, with several new localities having recently been found Portugal, Valencia, Catalonia and Aragon. Most of the Iberian Peninsula populations are small.
Flight Period
end of May to mid-August
Conservation Status
Similar Species
Gomphus vulgatissimus, Gomphus simillimus, Gomphus pulchellus
External Links
Genus: Gomphus
Gomphus is a genus of clubtail dragonflies in the family Gomphidae. As a result of phylogenetic studies, Gomphus subgenera Gomphurus, Hylogomphus, Phanogomphus, and Stenogomphurus were elevated in rank to genus in 2017. With the removal of their member species, Gomphus ended up with 11 of its previous 54 species.
Identification
Medium-sized dragonflies with a yellow to greenish body, with black markings. They have a diagnostic yellow line, almost uninterrupted, running from S1 to S7, or even S10. Eyes are clearly separated. The abdomen is club-shaped in most species, but lacks any leaf-like lateral flaps. The males have rather short, clearly diverging, upper appendages. The size is about equal to S10. The lower appendages are only slightly shorter, and their branches are largely eclipsed by the uppers when viewed from above. These short, splayed, eclipsing appendages are unique in Europe. The hindwing lacks an anal loop, therefore an uninterrupted perpendicular vein connects the subtriangle and the hind margin.
Separation from other genera
All gomphids in Europe are rather similar in general appearance and size, except for the large Lindenia and small Paragomphus. Males of both these genera bear abdominal flaps and have very long, parallel upper appendages. Ophiogomphus and Onychogomphus have an hind wing anal loop, and incurved upper appendages that do not eclipse the parallel branches of the lower appendage. Moreover, the Onychogomphus male appendages are long and pincer-like. Their abdomen appears ringed or spotted, rather than striped. In the field, confusion with Ophiogomphus is most likely, but mature adults are unmistakable because of their bright green head and thorax, as well as the yellow upper appendages.
When seen poorly, particularly in flight, females and immatures of some libellulids, particularly Orthetrum cancellatum, might resemble Gomphus. These have their eyes touching each other.
Separation of the species
Few of the genera of Europe seem as uniform as this one, and all nine species may be confused. The separation of three species (G. schneiderii, G. ubadschii, G. lucash) from their more widespread counterparts (G. vulgatissimus, G. simillimus) is still somewhat questionable, although the species in each pair are geographically (largely) separated.
Behaviour
Relatively shy dragonflies. The large numbers of exuviae found on river banks may correlate poorly to the occasional adult seen at the same site. After emerging, adults leave the water to mature in surrounding terrain, such as overgrown fields, borders and fallow land. These are often better places to search than the waterside. Mature males perch on twigs or rocks at the water's edge, waiting for females. At larger rivers they may also fly for long periods in midstream (G. vulgatissimus), or search the edges (G. pulchellus). It might be useful to search for individuals in the middle of the stream with binoculars. Females are especially shy, dashing out to open water, often in the centre of a stream, depositing many eggs in only one or several dips.
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.