… a blog by Buglife Cymru Conservation Assistant, Ashleigh Davies.
I work on the Coal Spoil Connections project, which aims to better understand the value of coal spoil sites for biodiversity and engage members of the public on the importance of these sites and the benefits that they can bring both people and wildlife. Part of the work we do is to survey the coal spoil sites for the rare and wonderful invertebrates that call them home. Last winter, we were out with local expert Christian Owen to map the distribution of the Maerdy Monster Millipede (Turdulisoma cf helenreadae) at Maerdy Colliery.
The Maerdy Monster was first discovered at Maerdy Colliery in Wales by Christian in December 2016. It’s a relatively small millipede at around 12mm in length which was named after the Maerdy Monster locomotive used at Maerdy Colliery when it was an active coal mine.
The Maerdy Monster is a new species to science, and as such we know very little about it. So, surveys are important, as they allow us to better understand why they live in the area they do and in the case of the Maerdy Monster, why they seem to rely on a coal spoil site.
The Maerdy Colliery site has a wide range of habitat types with different soil types, vegetation, temperature changes and gradients created by coal mining practices. We were keen to see whether the Maerdy Monster preferred certain conditions so that we can better understand the environment that it requires to survive. Throughout the survey, the most common places to find the Maerdy Monster was under damp rocks and wood debris.
Across the survey period from 2024 – 2025, we found a total of 29 Maerdy Monster millipedes, including 16 males, 11 females and 2 immatures. Repeated surveys help us understand where the Maerdy Monster is on the site, and if their numbers differ per year or can be found in new and areas. Coal spoil is mostly under-surveyed for invertebrates, and the surveys also help us to add more records of other species that we find. The data gathered can also use to inform Local decision making about the future use and management of cola spoil sites.
Other interesting finds on Maerdy Colliery
We have recorded lots more interesting species at the Maerdy Colliery, including the harvestman Sabacon viscayanum, the millipede Maurieseuma nontronense millipede and the Pyrenean Dusky Slug (Arion cf. iratii). Sabacon viscayanum is a mysterious arachnid that we don’t know much about. The Sabacon species lay these beautiful, clear eggs possibly a few times a year and are known to be able to stop laying their eggs if they feel threatened. The males have also been observed guarding the eggs from other males and predators when the female has long since moved on to a different area. They are speculated to be an introduced species, as its main locality appears to be in the Pyrenees. We also recorded the Pygmy Soldier Fly (Oxycera pygmaea) which relies on the niche habitat created by tufa springs – a type of freshwater spring that forms calcium carbonate deposits through chemical reactions with the air. Beyond invertebrates, we also came across rare mosses like the Stag’s-horn Clubmoss (Lycopodium clavatum). It is a protected species due to its rarity throughout the UK and is susceptible to habitat loss from fire and overgrowth from other vegetation.
Pygmy Soldierfly (Oxycera pygmaea) on Tufa © Liam Olds
Harvestman Eggs at Maerdy Colliery © Dave Hernon
As a Conservation Assistant, hands on survey training have played a large role in my new-found interest in invertebrates and other species. Learning more about the species only found within the boundaries of coal tips proves to me how special these sites are. It has been interesting how differently I survey an area since learning from other entomologists, by checking under rocks and fallen logs to search for species of invertebrates, fungi, lichens and bryophytes. Going through identification keys and looking through an eye scope to find the little details to identify what something is or if a creature is male or female has been exciting to learn. Each experience has added to my confidence and expanding knowledge of species found on coal spoil, which is something I will be forever grateful for from the Coal Spoil Connections team and the amazing people I have met through events and workshops throughout the year.
Main Image Credit: The Maerdy Monster (Turdulisoma cf helenreadae) © Liam Olds