Does anyone know what this is and what it belonged to? It was found by our volunteers last Thursday, down by the water's edge on Phase 1. Answer to follow next week....
There have certainly been plenty of these found around the sluices on Phases 1 and 2 in the last couple of weeks and despite the poor weather, the owners are making themselves quite obvious flying around the water's edge around the site.
It is indeed the exuvia (old larval case) of an emperor dragonfly, or Anax imperator to give it it's scientific name. The emperor dragonfly is the largest dragonfly to occur in the UK, with a body length of 80mm and a wingspan of around 100mm. It is a common species in southern England north to the Midlands and into Wales and is associated with lakes, large ponds, canals and ditches.
The female emperor dragonfly lays her eggs in floating pondweed. Depending on water temperature the eggs take around 3 weeks to hatch. On hatching, the larvae begin to feed on other invertebrates. They moult (shed their skins) 10-15 times during their development, with each stage in between moults known as an instar. Generally emperor dragonfly larvae take two years to develop fully, overwintering at the bottom of waterbodies and with most of their growth and feeding in the summer months.
In the final instar, the larvae migrates out of the water, adapts itself for breathing air and begins metamorphosis. On emergence the larval skin splits from just behind the head and the imago (adult) dragonfly emerges. The skin you see in the photo is what is left behind.
Odonata (dragonflies and damselflies) undergo incomplete metamorphosis, that is, there are only three life stages instead of four (as with complete metamorphosis). The three life stages are egg - larvae - imago and often the larval stage closely resembles the adult stage. Other insect groups that undergo incomplete metamorphosis are the Hempitera (true bugs) and Orthoptera (grasshoppers and crickets).