Keeled Skimmer – Orthetrum coerulescens
European common name: Keeled Skimmer
BDS pronunciation: or-thee-trum coy-roo-less-kenns
The Keeled Skimmer – Orthetrum coerulescens, is a recent addition to the County list. It’s smaller size and slender body help distinguish it from the similar Black-tailed Skimmer – Orthetrum cancellatum.
Classification:
| Odonata | |||
|---|---|---|---|
 | Anisoptera | Dragonflies | |
| Libellulidae | Chasers, Skimmers, & Darters |
The smallest Skimmer, similar in size to a Darter and noticeably slimmer than other Skimmers. Its smaller size and specific habitat requirements make it unlikely to be confused with other species in the region.
The male has a slender abdomen, covered with a blue grey pruinescence completely to the tip, only the appendages are black. A thin dark line, slightly raised in appearance, runs down the medial line of the abdomen and gives the Keeled Skimmer its common name. The eyes are blue. Immature males resemble the female in colouring, but with more prominent abdominal markings.
Females look rather like the Common Darter – Sympetrum striolatum, with a yellow thorax and a dark medial line. The medial line is crossed at the at the lower end of each segment, giving the appearance of a long inverted ‘†’ and is more noticeable in the female than the male. Unlike most female Skimmers, the abdomen doesn’t taper to any degree. The eyes are brown. Older females may develop pruinosity and colouring resembling the male.
The wings are clear, with long thin yellow orange pterostigma. Immature individuals have an amber suffusion running from the base to the middle of the wing, ending near the node.
Overall length: 36 – 45 mm
Wings: 28 – 33 mm
Most easily confused with other Skimmers and Chasers, but its specialised habitat requirements may rule out the Keeled Skimmer at many locations. The female is less like other female Skimmers or Chasers and closer in appearance to the Common Darter female.
- Broad-bodied Chaser – Libellula depressa
Has a more obviously broad and shorter body and features prominent basal wing patches. The male has noticeable yellow spots along the lateral line of the abdomen and brown eyes. The female is unlikely to be confused with the Keeled Skimmer, being much broader and with an obviously tapered abdomen. - Scarce Chaser – Libellula fulva
The Scarce Chaser is broader and has basal wing patches, and dark pterostigma. The male has distinctive black tipped abdomen and pale shoulder stripes. The female is more brown or orange coloured with a distinctive black line along the centre of the abdomen. - Black-tailed Skimmer – Orthetrum cancellatum
The male has a broader abdomen with a more extensive black tip and yellow lateral spots, the eyes are more obviously green rather than blue. The female is more yellow, with a tapering abdomen. - Common Darter – Sympetrum striolatum
Females resemble the female Common Darter which is similar in size, but lacks any noticeable shoulder stripes and has shorter and darker pterostigma.
Somewhat specialised habitat requirements, and is found most often in pools and streams in acidic heathland with peaty, boggy watercourses, which are not common in Bedfordshire.
Very restricted distribution and found only at Sundon Chalk Quarry where it’s reported as a breeding species.
Visible from late May to early September, peaking in June.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
| J | F | M | A | M | J | J | A | S | O | N | D |
Click for full size
External links for Keeled Skimmer – Orthetrum coerulescens:
British Dragonfly Society | Wikipedia
Gallery
