Sunday, 15 July 2012
Whilst exacavating the rockery to put in the waterfall this morning Brian found a dragonfly exuvia floating in the pond.
Dragonfly and damselfly nymphs live in water feeding on animals such as waterfleas, insect larvae and even tadpoles and small fish. They go through a series of moults and complete their development in one or two years although it can take up to five years for larger species. When development is complete they climb stems and leaves of bankside plants at night or early in the morning during late spring or summer. The adult will then emerge over the course of several hours. I have found exuvia (cast-off skins) on plants by our pond before but never been lucky enough to see an adult emerging.
Due to the well developed wing buds I am pretty sure a dragonfly emerged (you can see the exit hole behind the head) from this exuvia rather than it just being a cast-off skin from one of the nymph's moults.
The exuvia was around 45 millimetres long and around 5 millimetres wide.
The shape of the large eyes being almost half the length of the head with an angled rear edge, together with the size of the exuvia, suggest that this may be the exuvia of one of the Aeshna hawker dragonflies.
Unfortunately by the time I had found a dragonfly id guide after taking the first lot of photos and realised it was important to take a photo of the underside of the head and mouthparts to work out the type of labium, the exuvia had fallen off the barbecue and was now in two parts - so a very blurred picture of underside of the head.
My dragonfly identification skills are not particularly good and this is the first time I have attempted to identify which species may have emerged from an exuvia so if anyone can enlighten me more on which species this may be please leave a comment.
Edit - Apologies for the strange appearance of this post - whilst checking it in Preview half the typing seems to be in blue (no idea why!!).
FSC Guide to dragonflies and damselflies of Britain
WildGuides - Britain's Dragonflies by David Smallshire and Andy Swash published by English Nature