These guys may not be difficult to find, given the right habitat (vegetation-rich, shallow water), but care needs to be taken with identification, L. dryas being awkwardly similar to L. sponsa.
Both sexes are distinguished from L. sponsa mainly by their anal appendages (which are not always very clear). The male’s lower appendages are curved inwards and somewhat club-shaped. The female’s ovipositor is more prominent, reaching slightly beyond S10. The name Robust Spreadwing is actually very good because, once seen, L. dryas is more heavly built than L. sponsa and once seen, it can be quickly recognised, as I found at the amazing Lac Estivadoux in the Auvergne, France, which has a very large population.
[I have a comparison chart showing the distinguishing features of our four emerald damselfly/spreadwing species.]
- metallic green head, thorax and abdomen
- dark pterostigma (when mature)
- ♂ – develops powdery blue pruinosity on pronotum, side of thorax, S1 & front of S2, S9&10 of the abdomen
- ♂ – bright blue eyes
- ♂ – lower appendages are in-curved and clubbed (cf. L. sponsa where they are long & straight)
- ♀ – decidedly thicker abdomen (cf. ♂)
- ♀ – ovipositor extends slightly beyond tip of S10 (cf. other Lestes)
- ♀ – two green spots atop S1 essentially rectangular (cf. other Lestes)