The Emerald Damselfly – Lestes sponsa, is one of the county’s least common damselfly species. It’s larger than most damselflies but not always easy to spot.
Somewhat larger than the blue damselflies but smaller than a demoiselle or Willow Emerald Damselfly, characteristically rests with wings held half open at 45° or wider.
Upper surfaces of the male are predominantly metallic green, with a pale blue pruinescence developing on the lower half the of the thorax and segments 1, 2, 9 and 10 of the abdomen as it matures. The eyes also take on a blue colour as it matures, contrasting with the green head. The immature male resembles the female.
The female lacks the blue of the male, and the upper surface of the thorax and abdomen is metallic green, with the lower surfaces pale creamy-brown. Eyes are reddish brown.
Overall length: 35 – 39 mm
Wings: 19 – 24mm
Emerald damselfly species are very similar, but in Bedfordshire this is mostly likely mistaken for the Willow Emerald Damselfly – Chalcolestes viridis, particularly females. The Emerald is the smaller of the two, and emerges a little earlier in the year.
Careful examination of the thorax, pterostigma, and (male) claspers separates the two species, differences are summarised below:
|Feature||Willow Emerald Damselfly – |
|Emerald Damselfly – |
|Thorax||Upper (dark green) and lower (light green) surfaces. The darker area extends into the lighter with a noticeable ‘spur’, giving it a zig-zagged appearance||Upper (dark green) and lower (light green) surfaces with a straighter delineation between the two|
|Pterostigma||Pale, with obvious border||Dark brown|
|Abdomen: Male||All green, without pruinescence||S1, S2, S9, & S10 with light blue pruinescence|
|Abdomen: Female||S1 has a single unbroken dark green area notched at the top, giving the appearance of a solid ‘m’ or sideways ‘B’ shape||S1 has two dark green quadrant shaped markings, separate from each other|
|Claspers||Pale, straighter upper appendages, lower appendages short and barely visible||Dark, upper appendages noticeably curved, long lower appendages|
|Flight period||July – October||June – September|
Not generally seen over water, but found near shallow still water sites, ponds, ditches etc., sometimes around rivers close to still waters.
One of the county’s rarest species, but can be locally common at clay pits and quarries, such as Felmersham NR and Coronation Pit, although not always easy to spot.
Visible between early June and early September, peaking in July and August.