Jamie Bevan (CCW Warden of Crymlyn Bog and Pant-y-sias) wrote: 'Fen Raft Spider Dolomedes plantarius is currently showing well on the Tennant Canal, alongside Pant y Sais Fen. Known from only two other sites in the UK, it is one of Britain’s rarest spiders. With a leg span of up to 7 cm, it is also one of our largest. It spends much of its time on a ‘raft’ of vegetation on the water surface, using its front legs to sense the vibrations of its aquatic invertebrate prey. It is even known to catch small fish such as sticklebacks! During the breeding season the female spider constructs a nursery web within the marginal vegetation, in which she deposits an egg sac. Hundreds of tiny spiderlings hatch out from the egg sac, which then develop inside the relative safety of the nursery web, before dispersing into the surrounding vegetation a week or so later. The female spider often guards the web while the spiderlings develop. This is generally the easiest time to spot this striking but elusive species. Look for the nursery webs in large sedge tussocks fringing the canal, and the attendant female is usually very close by.'
Ed. Note that there now is new boardwalk at Pant-y-sais that provides great access to the fen. This can be found by walking along the canal towpath from the Jersey Marine end, or off New Road (B4290) at SS/7128 9409. If you park in the old car park head sw along New Road for a couple of hundred metres.