Does anyone know what this larva is? I found it while cleaning up after our Christmas tree was taken out.
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I agree that this looks like a devils coach horse larva and from the natural history museum website I note tha reproduction is by the laying of a single egg in autumn which reaches final growth stage (instar)about 200days later,given the size of this specimen this would just about fit the timescale if this is assumed to be the second instar(approx 130days from Sept 1st)
The adult and the larvae are carniverous and live in leaf litter which would be compatible with proximity to Christmas tree
The shape and colour are distinctive for cardinal beetle - see here http://www.flickr.com/photos/chirpy_uk/4432812910/
Rove beetle larvae tend to have disproportionately large heads (and single claws on each foot if you look closely to distinguish from ground beetle larvae) - here's a picture of a Devil's Coach Horse larva http://www.dgsgardening.btinternet.co.uk/devilchrse.htm
Cardinal beetle larvae are a fairly common sight under loose bark. Yours is probably Black-headed Cardinal P. coccinea but could be Red-headed Cardinal P. serraticornis (the commoner species). It is definitely not the other British member of the family Schizotus pectinicornis which has curved 'horns' at the tail.
Lat/Lng: 51.29, 0.993056
OS grid ref: TR087587