|6 of the 11 Sympetrum striolatum exuviae found in our garden pond (red rings) plus one more nymph just below the surface (blue ring)|
Exuviae also provide an excellent way of investigating juvenile Odonata morphology as the key nymphal features can be readily seen without needing to capture a specimen. Several dragonfly identification guides include sections on exuviae, but if you want to look at this aspect in detail, I recommend Cham (2007 & 2009) which are not expensive (and are now available as a single volume).
Cham, S. (2007). Field Guide to the Larvae and Exuviae of British Dragonflies. Volume 1: Dragonflies (Anisoptera). BDS, Peterborough.
Cham, S. (2009). Field Guide to the Larvae and Exuviae of British Dragonflies. Volume 2: Damselflies (Zygoptera). BDS, Peterborough.
Corbet, P. & Brooks, S. (2008). Dragonflies. Collins, London.