01 Aug Hunting for the Moon Spider
Jump to:
- Distribution in the UK and on the Continent
- Preferred Habitat
- Spotting a Moon Spider
- Current Threats
- How to Help: Life on the Edge
Distribution
The Moon Spider, Callilepsis nocturna, is only known to populate three locations in the UK: Pembrokeshire, the Isle of Wight, and Prawle Point – the Southernmost point in Devon.
Restricted to coastal habitats in England and Wales, the elusive arachnid has a much wider reach across continental Europe and Asia, residing as far north as Scandinavia, as far South as Iran, and as far East as Japan. Their Eurasian cousins differ in both behaviour and habitat, preferring to lurk beneath rocks in coniferous woodlands, rather than scurrying across the warm surfaces of south-facing wave-cut-platforms, a particular favourite of the South Devon variety.
Preferred Habitat
This preference for warm, coastal habitats likely stems from the spiders’ requirements for external heat to regulate their body temperature. Thermophiles – or heat-loving organisms – rely on an external heat source to speed up enzyme activity which boosts their metabolism, digestion, mobility, and reaction time. Additionally for some species, added warmth means that the young spiderlings and eggs develop faster.
Spotting a Moon Spider
Unfortunate, little is known about Moon Spiders. One of the aims of our Life on the Edge project is to observe and gather crucial information about their local populations, contributing to a better understanding of their behaviour and ecology.
On two balmy evenings in late May, we set out to do just that and were rewarded with a whole host of sightings! 20 individuals were identified, assuring us that the species is currently doing well in the area.
The best time of year to see them in Devon is from April to late May. If you plan to go out in search of the Moon Spider, here are some things you may want to consider:
Moon Spiders are small, only a few millimetres long, and devilishly quick. To make a positive identification, it is necessary to catch one and check for the eponymous silver dots, ‘moons’ , on the abdomen.
This can be done by placing a small plastic pot in a sunny are of open ground. This creates a make-shift sun trap, exploiting the creature’s warmth-loving nature. Leave the pot for a few minutes and wait to see if any come.
Whilst you’re there, why not take a look for the Long-horned Bee which is known to nest in the cliff faces above the wave-cut platform.
We were unable to observe the spider’s hunting behaviour, however it is thought that they are ambush predators that feed on ants and other small invertebrates. Over the course of the Life on the Edge project, we hope to observe more of their behaviours.
Under Threat
With 10 sightings recorded on our first trip, and another 10 when we returned to photograph the spiders, we now believe that they are locally abundant along this section of the coast, despite being range-restricted in Britain due to increasing pressure on their habitats.
Like many invertebrates, Moon Spiders need areas of open ground to hunt. Encroachment of scrubby plants like gorse and heather can quickly colonise open ground, crowding out other species of plant and casting broad shade over the ground surface. Whilst scrubland can provide important habitats for ground-nesting birds, it can quickly take over large swathes of land – bad news for the Moon Spider.
How to Help: Life on the Edge
The best way to manage these areas for wildlife is by breaking up scrub into patches of smaller habitat interspersed with grassland, dunes, or earthy banks. This creates a wide range of niches with varying shelter, light levels, and warmth, allowing a broader range of species to find the specific conditions to suit them.
The spiders at Prawle Point appear safe from encroaching scrubland for the time being, but we will be keeping a watchful eye on their population, monitoring their numbers and looking for opportunities to strengthen this stronghold for Devon’s wildlife.
