The Raft Spider Dolomedes fimbriatus on Thorne Moors:
An administrative error (!) but it may yet turn up.

If the impressive large dark chocolate-brown Raft Spider was to turn up anywhere in the Humberhead Peatlands it would be on Thorne Moors, but active collecting from the late 1960s onwards by invertebrate aficionados such as Peter Skidmore, Martin Limbert, Brian Eversham, Richard Wilson and the Ento section of the YNU had never encountered it. So it was with excitement that we read in Clifford Smith’s Yorkshire Spider Report for 1985 (Smith, 1986) the following tantalizing claim.

Dolomedes fimbriatus “Roger Key found abundant numbers among Eriophorum [Cotton grass] on Thorne Moors (SE740153) on drains leading to Swinefleet Warping Drain on 19th May 1979. This record has only recently been reported and it is hoped that other visits will make clear whether or not the species has become established. This is a first record for Yorkshire”.

This revelation prompted the inclusion of the record in a series of inventories and reviews of rare invertebrates, trumpeting the biodiversity significance of Thorne Moors and the Humber peatlands.

It was listed for Thorne Moors SE71 in the Invertebrate Site Register for South Yorkshire amongst species with occurrence status of Nr. [Nationally Rare]  (Key, 1986).

It was listed in Changes in the invertebrate fauna of Thorne and Hatfield Moors among species such as several of the rare spiders, including the jumping spider Bianor aurocinctus, recorded only from the older English gravings p.12. (Eversham,1991) and p.30. (Eversham & Skidmore, 1991).

On Thorne Moors its habitat/region code was deemed to be 1r [Peatlands, including acid moors, bogs and wet, peaty heaths, including acidic water-bodies in such places. Rare], its national status being L [Local] (Skidmore, 2006).

Doncaster Council included it amongst “Other rare species of the moors include the Large Heath Butterfly (Coenonympha tullia) (Thorne Moors only) and Bog Bush Cricket (Meconoptera brachyptera)” (DMBC 2007) and Natural England regarded it as a “Flagship species” of lowland bog restoration along with White-faced darter dragonfly Leucorrhinia dubia of bog pools; the Bog Bush Cricket Meconoptera brachyptera, typical of wet heath; and Large Heath Butterfly Coenonympha tullia (Smith, 2017).

At a recent YNU Entomological Section meeting I encountered Dr Key and asked him about his Thorne Moors record which he confirmed had been a clerical error, thus all references deriving from Smith (1986) need to be amended.

Further complications: At some time during the 1990s Peter Skidmore had handed me a tube containing a large black Lycosid-like (Pirate Wolf) spider with a cream band along each side of its cephalothorax. This, he had collected from a peat pool on Thorne Moors and wondered if it might be a Raft Spider. Though impressively large, I remember it being immature and thought it might have been a female Pirata piscatorious for which we already had records from peat pools and peat canals on the moors.

On 1 December 2019 a collecting tube containing a desiccated specimen of a Raft Spider was found amongst miscellaneous collecting materials which had been transferred to the author’s home (7 Aldcliffe Crescent, Balby) presumably during the removal of personal belongings from Doncaster Museum at the termination of the post of Environmental Records Officer back in September 2008. Though a paper label was attached to the exterior of the tube, I could find no writing in pencil or ink indicating provenance, date or collector. I had no recollection of the origins of this tube or its contents.

Since Natural England took over ownership and management of the Moors in 2004, it is possible that with their strong emphasis on re-wetting the peatlands, Dolomedes may spontaneously colonise by wind-assisted dispersal of spiderlings ‘ballooning’ on silken parachutes.

References
Doncaster Metropolitan Borough Council (2007) Lowland Raised Mire (LRM) Habitat Action Plan. Doncaster Local Biodiversity Action Plan. January 2007.
            [www.doncaster.gov.uk/biodiversity].

Eversham, B. (1991) Thorne and Hatfield Moors: Implications of land use change for nature conservation. Thorne and Hatfield Moors Papers 2: 3-18.

Eversham, B. and Skidmore, P. (1991) Changes in the invertebrate fauna of Thorne and Hatfield Moors. Thorne and Hatfield Moors Papers 2: 25-38.

Key, R. S. (1986) Invertebrate Site Register: Review of Invertebrate Sites in England – South Yorkshire. Report 76 II. Nov. 1986. Nature Conservancy Council, Peterborough.

Skidmore, P. (2006) An Inventory of the Invertebrates of Thorne and Hatfield Moors. Thorne and Hatfield Moors Monograph No.2. Thorne & Hatfield Moors Conservation Forum, Thorne, Doncaster.

Smith, C. (1986) Yorkshire spider report: 1985. YNU Bulletin No. 6: 27-29.

Smith, R.M. (2017) Catering for insect and spider assemblages in lowland raised bog reconstruction: a case study from the Humber Peatlands: 26-34 in Restoring the Humber Peatlands. Mid-term Workshop Report 27 September 2016. Natural England Life+Project LIFE13NAT/UK/000451.

CAH.