First off I am new to the site so would like to say hello .
While walking through Culbin forest today with my parents we came acroos the below pictured caterpillar in the middle of path, as you can see it has a dark head a peachy sort of colour underbelly and a dark reddish back. The caterpillar was also quite large being 2.5-3 inches in length and about 1/4-1/2 an inch in width. If anyone knows what this is would be greatly appreciated thanks.
Well what a super caterpillar. This is the caterpillar of the Goat moth, Cossus cossus. The caterpillars feed within the trunks of deciduous trees (very often oak) taking up to five years to become full grown. They then leave the tree to pupate in the soil and are, if you are lucky, occasionally seen as they crawl away from the tree. The trees often become riddled with exit holes from successive generations of moths and often have a distinctive 'goaty' odour - hence Goat moth. Lepidopterists know such trees as 'goat trees' - I know several but have never had the good fortune to be near one when a caterpillar has made a run for it.
Oh, and I should add that it is not a common moth/caterpillar and has a widespread but local distribution in the south becoming more scarce in the north.