Looking for a needle in a haystack…and finding it!

Last Friday I found myself crouched over a plastic sheet in the middle of a National Nature Reserve, squinting at Sphagnum. I’d joined an enthusiastic team of local spider experts, volunteers and Natural England staff at Fenn’s, Whixall and Bettisfield Mosses, a NNR spanning the English and Welsh border. Our mission: to search for the nationally rare spider species Glyphesis cottonae. 

This is a special spider. A UK Biodiversity Action Plan priority species and a Section 41 species, it has only been recorded in four hectads (10km x 10km squares) nationally since 1992.  G. cottonae hasn’t been found at Fenn’s and Whixall Moss since 1994.

The species is something of a specialist, living in lowland Sphagnum bogs, in areas where there is a reasonable growth of Sphagnum above the water level. This limits its distribution nationally, as such habitats are extremely rare. It is also tiny – with a body size of c. 1mm. This, coupled with the specialist methods needed to find and identify it, means that it is very likely to be under-recorded. It may be more widespread than currently thought; it may even be locally common in some Sphagnum bogs. The point is that, currently, we just don’t know. Any record therefore has the potential to contribute greatly to our understanding of this species and its habitat requirements.

Because of its small size, G. cottonae needs to be searched for extremely carefully. Small clumps of Sphagnum are removed from the bog, placed on a white polythene sheet and carefully teased apart. Keen volunteers huddle on the heather, knees slowly soaking up water. Eyes strain for any darkly coloured movement. The wind howls; a nearby snipe loses its nerve and breaks cover. Then suddenly… “spider!” A tube is grabbed by frozen fingers, and a small speck of spider is captured.

There is no way of knowing in the field whether any individual is G.cottonae; it is so small that identification can only be confirmed by a specialist using a powerful microscope (for those who are interested, apparently the pattern of the dorsal spines on the tibia, the absence of spines on any metatarsi, and the structure of the epigyne - female reproductive organ - are diagnostic!).

Excitingly, Tom.bio has just heard that local spider experts have provisionally confirmed that some of the spiders collected last week are indeed G. cottonae. Identification of this species is so tricky that it needs to be confirmed by a second opinion; however, we are cautiously optimistic!

G. cottonae, along with other species of Sphagnum bogs, are threatened by the loss of heathland and the drainage of associated bog systems by agriculture, afforestation and development. By monitoring and recording this tiny spider, and seeing how it fares over time, Natural England can gain insights into the current health of the bog and whether their management techniques are proving effective for this species.

It is also a brilliant hook to engage people with – a ‘spider hunt’ for a nationally rare species, using an unconventional sampling technique in a beautiful location, certainly inspired me. It may not be the most charismatic of creatures, but G. connonae punches above its weight!

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Thanks to N Cane-Honeysett, A Allot, P Bowyer and J Daniels for G. cottonae facts.