Orthetrum trinacria
Orthetrum trinacria (Selys, 1841)
Local names: Long skimmer, Langer Blaupfeil, Lange oeverlibel
Species Information
Description
This is a large, elongated and powerful species. It is rather aggressive and may recall an Aeshnid in flight. Unlike its cogeners it has a very long cylindrical abdomen, with a bulbous base that makes it unmistakeable. It has light-blue or light-blue-grey eyes. The pterostigmas are long and pale yellow in colour outlined with black. The terminal appendages are very long.
Immature and female individuals are greenish yellow in colourwith dark markings on the abdomen similar to those of Orthetrum cancellatum but with an additional black line along the centre. Legs are yellow with a black line.
Mature males turn to dark slate grey with reduced and thin light-blue pruinosity. The legs take on a black colour. This makes this species darker than other Orthetrums. Also the mature females tend to darken and develop a blueish pruinosity.
It is unique for:
- Length always over 50 mm (O. cancellatum about 10 mm shorter on average)
- Uniformly slender S3-S10
- Black abdomen with pale streaks at least up to S7, rather than rings up to S6. The longest part of the pale spots on S4-S6 lies against the dorsal keel, not along the lateral keels as in O. sabina
- Males and females darkening, with relatively thin bluish pruinosity, appearing darker than other pruinose Orthetrum males. The abdomen may appear largely black.
The abdomen shape may recall the much smaller O. chrysostigma which is marked differently. O. sabina is smaller, never pruinose, is differently marked and never has grey-blue eyes.
Size
Habitat
In Europe significant populations are restricted to lentic systems such as man-made reservoirs and large open sunny ponds, pools and marshes with well-developed bank side vegetation. More rarely the species is found at slow-flowing stretches of rivers. In Morocco it occurs at coastal marshes and ponds, but more recently it has established itself further inland, taking advantage of man-made barrage lakes. It was also found to be common at concrete water tanks lacking any vegetation in the oases of the northern Saharan fringe in Morocco. The species is restricted to lowland areas.
Distribution
Othetrum trinacria is a common and widespread Afrotropical species and occur throughout most of the African continent. It is moderately common in northern Africa. Outside Africa it occurs in parts of Mediterranean Europe and the Middle East. Although originally described in Europe from Sicily in 1841, it has a limited range in Europe. IT was discovered in Sardinia in 1972, followed by discovery in Spain 1980, Portugal 1991, Fuerteventura in 2000, the Maltese islands in 2003 and mainland Greece in 2011. The records of wanderers on Pantelleria, Lampedusa and COrsica illustrates its ability to reach and colonise remote islands. The species has recently established itself on the Maltese islands. It is now well-settled in the entire south-western region of the Iberian Peninsula, extending and approaching the Ebro Delta in the east. It is now relatively common in Extremadura, Algarve, Sicily and Sardinia. The species is remarkably scarce in mainland Italy, although it was recently found in Calabria. Given its expansion in Syria and Turkey, it is possible that this species will appear on the east Aegean islands in the future.
Flight Period
From mid-June to mid-October
Behavior
Aggressive. In Africa known for frequently preying on other dragonfly.
Conservation Status
Similar Species
Orthetrum chrysostigma, Orthetrum sabina
External Links
Genus: Orthetrum
Orthetrum is a large genus of dragonflies in the Libellulidae family. They are commonly referred to as skimmers.
Identification
Almost every blue to grey pruinose dragonfly with clear wings will be an Orthetrum male. The combination of a clear base, at most yellow-tinted, and 10-14 forewing cross-veins (thus last antenodal one is complete) is unique for a libellulid.
separation from other genera
Libellula species are similar in venation, stature and pruinosity, but have large dark patches at the hindwing base. Pruinose Leucorrhinia species are dark, with a contrasting white face and also dark hindwing patches. The rather plainly brown females and young males of most Orthetrum species are often mistaken for Sympetrum and Crocothemis. The species in both these genera normally have the last antenodal cross-vein incomplete; Sympetrum has only 6-7 complete forewing antenodal cross-veins, and Crocothemis has large yellow patches at the hindwing base. Especially fresh yellow O. cancellatum and the club-tailed black-and-pale O. sabina superficially resemble gomphids, but their eyes touch each other.
Separation of the species
Some 60 Orthetrum occur in Australia, Eurasia and particularly Africa. The species are often difficult to identify. This is especially true for males, whose markings have become obscured by pruinosity, thus appearing very unlike females and younger males. For convenience, the species can be divided into three groups. In most of Europe, separating O. albistylum from O. cancellatum (group 1) and O. brunneum from O. coerulescens (group 3) will cause the greatest difficulty. In the Mediterranean, two diagnostic species in group 2 and three additional species in group 3 occur. Because up to four species of species group 3 may occur together in Iberia, north Africa or Turkey, identification might be difficult. Examination of the male's secondary genitalia with a hand lens will be most decisive.
| Group | Species |
|---|---|
| Group 1 | O. albistylum O. cancellatum |
| Group 2 | O. trinacria O. sabina |
| Group 3 | O. brunneum O. chrysostigma O. coerulescens O. nitiderve O. taeniolatum |
Behaviour
Active species, often perching on the ground or stones. Male guards the female during oviposition, usually by hovering above her and chasing off rival males.
Family: Libellulidae
The skimmers or perchers and their relatives form the Libellulidae, the largest dragonfly family in the world. It is sometimes considered to contain the Corduliidae as the subfamily Corduliinae and the Macromiidae as the subfamily Macromiinae. Even if these are excluded, there still remains a family of over 1000 species. With nearly worldwide distribution, these are almost certainly the most often seen of all dragonflies.
The genus Libellula is mostly New World, but also has one of the few endangered odonates from Japan: Libellula angelina. Many of the members of this genus are brightly colored or have banded wings. The related genus Plathemis includes the whitetails. The genus Celithemis contains several brightly marked species in the southern United States. Members of the genus Sympetrum are called darters (or meadowhawks in North America) and are found throughout most of the world, except Australia. Several Southern Hemisphere species in the genera Trithemis and Zenithoptera are especially beautiful. Other common genera include Tramea and Pantala.
The libellulids have stout-bodied larvae with the lower lip or labium developed into a mask over the lower part of the face.
The family name may have been derived from the Latin libella which means booklet.