Counting skins

As stated in Corbet & Brooks (2008), when looking at Odonata (dragonflies and damselflies), the 'value of the exuvia as a tool for quantitative ecological studies cannot be overstated'. This is because, in Britain at least, most species can be identified from their exuviae (moulted skins) which show where and, depending on the fequency of recorder visits, when an adult emerged, even if the adult is never seen. This is how, despite only seeing single adults, I know that 11 common darters (Sympetrum striolatum) have emerged from our garden pond even though it is only a year old and around 3m x 1.5m in size. The exuviae are easy to find and count - as the photo here shows, they can be clustered closely together and may be on even very short emergent vegetation.

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).

References


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.