Black-tailed skimmer

Black-tailed skimmer
Male, Tallinn Estonia
Female, Norfolk, England
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Odonata
Suborder:	Anisoptera
Family:	Libellulidae
Genus:	Orthetrum
Species:	O. cancellatum
Binomial name
Orthetrum cancellatum (Linnaeus, 1758)

The black-tailed skimmer, Orthetrum cancellatum, is a dragonfly of Europe and Asia. It occurs nearly all of Europe except northern UK and Scandinavia; to the east, the range extends to Kashmir and Mongolia.

The adult male has a blue abdomen with a black tip and transparent wings, and the female has a yellow (later: brown) body with black bands along the abdomen and transparent wings. Even the immature males look that way.

This species has expanded its range, assisted by the creation of gravel pits which give it the extensive open unvegetated areas it prefers. It was first recorded in Great Britain in Essex in 1934. It is decreasing rapidly in the Maltese Islands.

Description

The black-tailed skimmer is a fairly large dragonfly (the length of 44–50 mm, 29–35 mm abdomen, rear wing 35–41 mm.) with relatively broad, flattened abdomen, but not as broad as to chaser species. With age, adult males develop extensive blue pruinescence on their abdomen, offset by yellow lateral patches. The middle lobe of the pronotum is large and notched in the middle. The chest is yellow or yellowish-brown. The abdomen is more or less flattened. The base of the hind wings without a dark opaque spots. The pterostigma is dark brown or black. On the front wings pterostigma 2–3 mm long. Anal appendages black. The females and immature males are a deep yellow color, with wavy black lines dorsally on their abdomen. Males and females have the costal vein (the leading edge of the wing) yellow or black.^[1]

The species is similar to its much more localized congener the White-Tailed Skimmer, but readily identifiable in the field. The males develop a blue pruinescence on the abdomen darkening to the rear with S8-10 becoming black. Its eyes are very dark green. They fly swift and low, skimming the water surface. Females retain their color and markings though they become quite grayish brown with age. This species could be confused with Keeled skimmer or Scarce chaser.

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  young male
• 
  adult male
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  Young female
• 
  Female
• 
  Female

Adults

Adults about 47–53 mm long. Average wingspan is about 77 mm; hindwings 35–40 mm long.The eyes dorsally narrowly apposed to dorsally broadly contiguous; brown (in the female), or blue (in the male).Legs black and brown (the femoral bases brown). Thoracic antehumeral stripes absent. The wings spread more or less horizontally in repose; dissimilar in shape and venation; sessile; unpatterned and clear. The inner wing venation blackish. Discoidal cell divided longitudinally into a conspicuous triangle and supra-triangle. Antenodal veins in the forewings 10–13 (fewer in the hindwings).^[2] Pterostigma well over twice but no more than five times as long as wide.Abdomen lanceolate 30–35 mm long; predominantly blue (in the male), or brown (in the female), or grey (sometimes, in old females); rather plain (in the male, but often with orange lateral markings, and darkened over the terminal segments), or predominantly longitudinally lined (the female with a dark medio-lateral band on either side along each segment); without mid-dorsal spots.^[3] The male abdomen without auricles on segment 2; with a single inferior anal appendage. ♂: Adults have a bluish or blue-gray patina on the body, gradually darkening with age. The young have a grid pattern on a yellow-brownish abdomen. ♀: Yellow-brownish abdomen with a lattice pattern (wide longitudinal dark brown stripes and bright crescent-shaped spots). 10 tergite of abdomen black.

Nymphs

The nymphs are stout, body is expanded in the middle. When mature,they are 23–25.5 mm long.The postocular lobes curving sharply to the back of the head from some distance behind the eyes. The antennae 7 segmented.^[4] The mask having the prementum hollowed dorsally. The prementum bearing three (rarely two or four) long setae inserted near each lateral margin, and two medial fields of seven to eight short spiniform setae, the latter flanked by four setae of medium length. The body of the labial palps bearing 6 or 7 major setae. Distal margins of the labial palps weakly crenate. Legs longer than the abdomen.The abdomen terminating in five short spine-like appendages. The cerci no more than half the length of the paraprocts. The abdomen with mid-dorsal spines. The mid-dorsal abdominal spines prominent on segments 3 to 6. The abdomen without a mid-dorsal spine on segment 8; gizzard with 4–8 folds.^[5]

Mating

mating wheel

Oviposition site and behavior: females oviposits alone but with male in attendance. Eggs are laid in flight by dipping abdomen onto water surface.^[6] They hatch after five or six weeks and the larvae live partially hidden by bottom debris. They emerge after two or three years.Larvae prefer bottom areas rich in vegetation and decaying plant material. The main flight period is June and July.^[7] Males characteristically perch horizontally on exposed surfaces. They fly swift and low, skimming the water surface, while defending their territories. Mating can occur in flight or on land.^[8]

Distribution

Fairly common. Orthetrum cancellatum is a widespread European species which occurs eastwards over central Asia to the northern parts of China and Arunachal Pradesh in India. It is found throughout European continent including the Mediterranean islands but is absent in the north of Britain. This is one of the most common European species. This species is still increasing its range northwards.

It is native in Albania; Austria; Azerbaijan; Belarus; Belgium; Bosnia and Herzegovina; Bulgaria; China; Croatia; Cyprus; Czech Republic; Denmark; Estonia; Finland; France (Corsica, and mainland); Georgia; Germany; Greece; Hungary; India; Ireland; Italy ; Kazakhstan; Kyrgyzstan; Latvia ; Lithuania; Luxembourg; Macedonia, Malta; Moldova; Mongolia; Montenegro; Netherlands; Norway; Poland; Portugal; Romania; Russian Federation; Serbia ; Slovakia; Slovenia; Spain; Sweden; Switzerland; Tajikistan; Turkey (Turkey-in-Europe); Turkmenistan; Ukraine; in part of United Kingdom;^[9] Uzbekistan.

The black-tailed skimmer is abundant throughout its range and is one of the most commonly seen dragonflies in Europe. It holds a stable population and has no known major threats.^[10]

Habitat

This dragonfly is found at any open water with bare patches along the shore where the patrolling males frequently rest in the sun. Also near slow-flowing waters. Favors lakes, slow rivers, ponds and sometimes marshy area, without dense riparian vegetation.^[11] Females are less bold and not encountered as regularly. Adults prefer to perch on bare ground and rocks.

References

Sources

• "Orthetrum cancellatum". British Dragonfly Society. Retrieved 14 October 2010. 
• Klaas-Douwe B Dijkstra, Richard Lewington, 2006: Field Guide to the Dragonflies of Britain and Europe. British Wildlife Publishing, Gillingham.
• A. Sciberras, 2008: A Contribution To The Knowledge Of Odonata In The Maltese Islands. The Central Mediterranean Naturalist 4(4): 275-288.

External links

• DragonflyPix
• NatureSpot
• Habitas
• iNaturalist

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