The Lyons Share

The Spiders of Sussex Chalk Pits

Posted by Graeme Lyons , Thursday, 16 February 2023 10:17

It's been a rough start for the year but despite this, I am ahead of the game for once with work. I needed a new project to focus my recording efforts. In 2021, some of my most exciting spider finds were in chalk pits, at Amberley Chalk Pits (chiefly, Centromerus albidus found whilst looking for other rarities - a species not seen in the UK since 1969!) and at a small pit at Iford. This got me thinking, how many more of these small sites are there out there and what might be hiding there? Many of them seem to have never been looked at for biodiversity in anyway. 

They are often not that inviting, the one in the image above was huge but mostly vertical and clearly only the base was accessible, while others are a little easier to record. There are loads of them, peppered around the South Downs (just drive along the A27 and look for big white patches) and I am only just starting to get a mental map of where they are and who owns them, so that I can start gaining access.

I have data for nine sites so far, six of these are historic (and two of these represent full surveys) and three are from new sites I have looked at in the last two weeks. 

I have pulled all this data into one matrix, with species down the side and each quarry listed as a column on the spreadsheet. Amazingly, this is already up to 97 species of spider and even more amazing, 18 of these have conservation status (18.5%). Clearly, chalk pits hold a significant number of rare and specialised spiders. Of these 18, five species are listed as Nationally Rare.

It's not just spiders, I have recorded 531 species so far in these nine pits, 384 of which are invertebrates.

What are the outputs of this survey, I hear you ask?

• Enjoy myself at a relaxed pace.
• To find and access as many chalk pits as possible with landowner permission and get me to some new, bite-sized, close-to-home, unrecorded areas of Sussex.
• To record as many spiders as possible in these pits.
• Use some subterranean/pitfall traps in a few places.
• To record other taxa in a casual way, whilst doing the above.
• To take some very basic chalk pit biometrics.
• Percentage chalk/vegetation
• Slope
• Aspect
• Presence of scree
• Presence of sievable moss
• Write it all up at an undetermined timescale. I'm talking years not months.
• Use the data collected to generate a list of "Chalk Pit Indicator Species" (CPIS) of spiders and analyse using the biometrics to assess and the rank the assemblage of chalk pits in Sussex for their spiders and other wildlife.

The others were the ubiquitous Agyneta mollis (this over-designated spider is listed as Nationally Rare, Near Threatened and Section 41). My hunch is that it should not even be Nationally Scarce. It is now the most frequently recorded spider with status that I record, and the third most frequently recorded invertebrate with status that I record (after Small Heath and Lygus pratensis). I am working on proving this spider is not a conservation concern, it's not habitat restricted, it just likes open places. I have even found it on boring lawns with the sucker. The other two were both surprises. Theridiosoma gemmosm and  Monocephalus castaneipes (this latter is not a common spider in Sussex).

What I think is also really cool, is that the entire insect is covered in huge pits, each filled with muddy chalk. It's a walking chalk pit assemblage, and a fitting find for the start of my chalk pit survey. It's also a great thing to find when you are writing a book about pan-species listing, as it goes to show that when you are surveying for one specific thing like spiders, if you have an approach where everything counts and anything is fair game, then you can come away with your highlight being something totally different, in this case a stonking weevil!

Posted in beetles, birds, bryophytes, chalk pits, liverworts, spiders