Orthetrum albistylum
Orthetrum albistylum (Selys, 1848)
Local names: White-tailed skimmer, Östlicher Blaupfeil, Witpuntoeverlibel, Vitstjärtad sjötrollslända
Species Information
Description
Very similar to Orthetrum cancellatum with which it sometimes co-occurs. However it is leeker, paler and more contrasting and have different white-coloured appendages (hence the name of the species) in both sexes. The females and immature males are black and yellow, the abdomen has two longitudinal black lines on the upper side of the abdomen.
The mature males get the abdomen covered in light-blue pruinosity, except for the last segments that darken into black. The blue pruinosity get lighter in colour with age. The species has black pterostigma like Orthetrum cancellatum from which it can instead be distinguished by the white appendages and also the more slender abdomen. Besides the white appendages, in the females also the last segment is white. On the sides of the thorax there is two light-coloured bands.
Size
Habitat
Orthetrum albistylum is found at a wide range of sunny standing and , more rarely, at slow-flowing waters. In the Mediterranean region, it is also found at small intermittent streams with residual ponds in the summer. It favours relatively shallow areas where part of the fringes dry up in the summer, but can also be found in deeper waters with steep banks such as fish ponds. This species appears to have a preference for man-made habitats, including quarries, sandpits and fish pond and is largely confined to such areas in its northern range, where it often acts as pioneer species. ITs occurrence in more natural habitats includes oxbows, pools in floodplains, shallow ponds with extensive reed beds and peaty ponds and lakes surrounded with banks and rafts of Sphagnum peat moss, sedges and rushes. The water quality can vary from acidic and mesotrophic to neutral and eutrophic with low transparency. The water bodies often have submerged or floating vegetation such as watermilfoil and/or waterlilies. The species appear not to be dependent on bank side vegetation and is able to cope with the presence of fish, although it does require high water temperature, which is probably a key factor for its establishment. It is mainly confined to areas below 500 m but has been found breeding up to 860 m in Switzerland.
Distribution
The core of the European distribution range of Orthetrum albistylum runs from south-west France to the southern half of Poland, the Balkans and Ukraine. In some regions, for instance the Pannonian Basin and south-western Ukraine, it is among the most abundant Orthetrum species, outnumbering its close relative, O. cancellatum. The species appear to be widespread in eastern Ukraine and, at least in the past, the south of European Russia, reaching both sides of the Caucasian and connecting with Turkish and the few north Iranian populations. It is virtually absent from the Mediterranean islands, although two records are known from Crete. Its near-absence from the Iberian Peninsula and central and southern Italy is notewothy (one record each) and cannot be readily explained by the lack of suitable habitats or by climatic conditions. Its northern distribution within Europe seems, to a large extent, to be determined by summer temperatures and the species is currently exhibiting a continued northwards expansion.
Flight Period
June to September
Behavior
It is a very aggressive species that often preys on large insects and even other dragonflies. The mating starts in flight and the couple might even fly for some distance in the mating wheel. The end of the mating is marked by the male finding a suitable place to perch. Immediately afterwards the female will begin to oviposit while the male clashes with other males and jealously guards her. In this species the dragonflies tend to congregate at the places suitable for oviposition and it is not unusual for the female to be grabbed several times before she can start to lay her eggs. The males often perch directly on the ground or on man-made structures.
Conservation Status
Similar Species
Orthetrum cancellatum, Orthetrum brunneum, Orthetrum coerulescens
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.