Bladetail  (Lindenia tetraphylla)

The bladetail has yet to be globally assessed, but it is classified as Critically Endangered (CR) on the Red List of Northern Africa (2).

The bladetail (Lindenia tetraphylla) is a large but slender dragonfly species with attractive markings, and is the largest member of the Gomphidae family to be found in Europe. This elegant species gets its name from the four ‘blades’ located underneath the tip of the abdomen (3).

The thorax and abdomen of the bladetail both have a sandy grey base colour (3), and the thorax is decorated with four curved black stripes which form two ring-like patterns at the front. In the female bladetail, the front of the head is yellow and does not have any marks or spots, while the eyes are thought to be grey (4).

Dragonflies, such as the bladetail, can be recognised by their long wings and their large, globular eyes and short antennae. In many dragonfly species, the eyes touch each other (5) (6). However, the bladetail differs in this respect, as the eyes are spaced apart (4) (7).

The range of the bladetail stretches eastwards from Italy, through Greece and across the Arabian Peninsula, as far as Kyrgyzstan and the boundary between Pakistan and Afghanistan. A single record exists for this species in Spain, but this dates back to 1921. The bladetail is found as far north as the Aral Sea, the Black Sea and Slovenia, while in the south its range runs through Israel and is limited by the coastal area of North Africa (8).

The bladetail was once found in Algeria, but is now thought to be extinct in the country (6), and no records of this species seem to exist in the last century for North Africa (8).

Areas of standing water, such as large lakes, are the preferred habitat of the bladetail (8) (9), and this species is often found within sandy areas around such water bodies. The bladetail tends to be found around nutrient-poor yet oxygen-rich water bodies (8).

The specific habitat requirements of the nymphal stage of the bladetail are not known (8), although the nymphs are thought to live in freshwater environments, both in still and in running waters (6).

Very little information is available on the biology of the bladetail (8). However, reproduction in dragonflies generally involves very little courtship behaviour, and begins with the male grasping the female by the back of the head with the anal claspers. Mating then takes place in the air, on the ground or among vegetation, with the length of the process varying greatly between species (10).

Like other dragonfly species, the bladetail is thought to have a complex life cycle which includes a fully aquatic nymphal stage (10). As a nymph, the dragonfly is an effective sit-and-wait predator with the unusual feature of being able to fire out the lower portion of its mouth in order to grasp passing prey (10) (11).

As well as being able to walk, dragonfly nymphs are able to move through the water by jet propulsion, expelling water from a specialised rectal chamber in order to propel themselves along (11). The total length of time spent in the nymphal stage varies between dragonfly species, with some species spending a few months and others several years as a nymph (10).

Adult dragonflies are skilled aerial predators, usually catching various small insects on the wing (10).

The adult bladetail has been reported to roam over relatively large distances, and as a result it is thought that this species is able to recolonise old sites or settle in new bodies of water. This ability to colonise unstable, arid environments is a result of a combination of factors, including the migratory ability of the adults, their preference for breeding in stagnant water, and the fact that the nymphs are able to tolerate salinity (8).

The bladetail is at risk from activities which involve the disturbance of water bodies, such as hydrological regulatory works, while water pollution is a further concern (9).

The increasing recreational use of water resources in countries in which the bladetail is found, particularly within the Mediterranean region, poses a future threat to this species. Disturbance of the lakes and other areas the bladetail prefers could also negatively affect the breeding potential of this species (8).

However, in most of its range, the bladetail may still be unthreatened (8).

The bladetail is listed on Annex II of the Bern Convention, which means that it should be strictly protected in Europe (12). This species is also listed under Annexes II and IV of the EU Habitats Directive, meaning that the bladetail is in need of strict protection, and that this will require the designation of special areas of conservation (13).

As the bladetail is most commonly found in large, nutrient-poor but oxygen-rich lakes, recommended conservation actions for this species focus on the protection of such areas, particularly in Greece and Sardinia (8).

Further recommendations for the bladetail include research into the habitat requirements of its nymphs, as well as into the general ecology of this little-known dragonfly (8).

Find out more about the conservation of dragonflies and damselflies:

• Moore, N.W. (Ed.) (1997) Dragonflies - Status Survey and Conservation Action Plan. IUCN/SSC Odonata Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK. Available at:
  http://data.iucn.org/dbtw-wpd/edocs/1997-042.pdf

More on invertebrates and their conservation:

• Buglife - The Invertebrate Conservation Trust:
  http://www.buglife.org.uk/

Find out more about the habitat of this species:

• ARKive - Mediterranean Basin:
  http://www.arkive.org/eco-regions/mediterranean-basin/