Meta menardi is a large, dark brown, orbweb spinning troglophilic cave spider that is well known to cavers. Meta spiders need space to create these webs, but they are not spun across the cave passage like normal orb spiders unless there is nothing else to anchor the web to. The threads of the web of Meta menardi are not sticky and appear to serve as a supportive platform for the spider rather than directly serving to trap prey, instead the radial threads act as a series of trip lines to detect the presence of potential prey on the cave walls and ceiling.  They feed on woodlice, millipedes, slugs, earthworms, flies (Culex pipiens in particular) and possibly smaller Meta menardi (although there is no evidence of this). It can gorge itself and may store food by trussing it in the web.

Meta menardi inside entrance to Cox's Cave.

Meta menardi prefers reflected light and dim zones (not direct light) and appears to live slightly deeper in a cave during the winter. Movements of different species towards or away from the threshold at different times of year may change the dynamics of the spider’s diet. It also appears to prefer vertical shafts, presumably because more prey might fall in. The webs are orientated away from light – at 90 degrees and are to be found in the shadows e.g. in phreatic pockets and scallops – by spinning them here they may trap fungus gnats seeking shade or maybe they are simply harder for prey to spot.
The female lays a clump of eggs and spins a silk cocoon around them for protection. You may see these hanging from the ceiling. 

Metellina merianae (formerly in the genus Meta) is found in the threshold, often at the entrance itself where it spins an orb web to catch creatures flying in and out of the cave. It is a similar shape to M. menardii, but is smaller, lighter brown with dark spots on the legs. It is generally found in the shallow threshold zone, whilst Meta menardi is often found deeper in the cave.  The two species are frequently recorded from the same caves. 

In cracks and pockets in the cave threshold you might see Nesticus cellanus – its web consists of long threads stretching down to the floor and out to the walls – at the base of these threads are sticky droplets to catch crawling insects – in this way it avoids competing for the same food as Metellina merianae.

Linyphiidae in Read's Cavern. The mass of webs are coated in moisture.

There a number of small spiders belonging to the Linyphiidae family ('money spiders') e.g. Neriene sp., Porrhomma sp. that are found in caves. Porrhomma.convexum is common and has been recorded from Blake’s Farm Cave, Sidcott Swallet, Stoke Lane Slocker and Swildon’s Hole.  P. egeria has been recorded from Elm Cave and Goatchurch. Porrhomma sp. webs are often in obscure cracks and crevices in the walls of the cave, and the spiders even harder to spot.  Other 'money spiders' include Lophocarenum nemorale, Lessertia dentichelis, Erigone dentipalpis, Centromerus prudens and three species of Lepthyphantes: L.  pallidus, L. zimmermanni and L. ericaeus.
Spiders may not have many predators in the caves - bats do not appear to be interested, except possibly Natterer's bat (Myostis natterei) in caves during cold weather or when hibernating.

The Cellar or Skull spider Pholcus phalangioides in the roof of the entrance to Gough's Cave. These eat other spiders and insects, even each other.

Three species of Harvestmen (Opiliones) have been recorded from the threshold of several Mendip Caves, including Phalangium opilio, Liobunum blackwalli and Nemastoma chrysomelas.  These are all accidentals, their true habitat being the matted grasses and loose soils around the entrances. Unlike spiders, harvestmen have no venom, they also only have one pair of eyes so their vision is not as good. They have no silk glands and do not spin webs.

Pseudoscorpions are small and abundant arthropods but are difficult to spot as they are only 2-4mm in length. They are aggressive hunters and use their enlarged pedipalps to catch prey. Once it has sucked up the contents of its prey it can survive for weeks even months without another meal. They may have small territories - this one was found in exactly the same place 2 weeks later.

Pseudoscoropion (Chthonius sp.) in Fairy Cave

Mites are small relatives of spiders. There are a number of mites found living in Mendip caves, including members of the genera Eugamasmus and Rhagidia, as well as a variety of other genera and species.  Many of the records are thought to be of accidentals (possibly blown into caves or brought in on the mud on cavers’ boots) but some may be regarded as troglophiles (e.g Veigaia transisalae and some members of the Eugamasus magnus group) and possibly even troglobites (e.g. Rhagidia spelaea) in Britain. 
Some mites are truly microscopic and go unnoticed. They live in a variety of habitats - some free-living, some parasitic on plants and animals, others preying on Collembola and other small insects.  Water mites (Hydracarina) are another group that require further study and will no doubt add to the list of mites found in Mendip caves.   Several species of water mite are only known from deep in water-filled gravels. 

Rhagidia sp. mite in Withyhill Cave. The other creatures in the photograph ar springtails.

Rhagidia mites run about quickly with no apparent purpose except possibly to hide from your light.

Parasitic ticks and mites in caves are associated with bats. The most common tick on bats is Ixodes vespertilionis, the female lives on the blood of the bat and is closely associated with caves.

Centipedes are normally regarded as soil organisms and there have been few recordings from caves. They are predators feeding on nematodes, mites and other smaller insects.  The most common species that might be encountered is Lithobius dubosqui (Goatchurch Cavern), a small, rather short-bodied species that might be regarded as a possible cavernicole.  Other species that have been recorded (generally in the threshold) include Lithobius forficatus (Sandford Levy) Lithobius pilicornis (Gough’s Cave), Lithobius variegatus (Great Oones Hole), Lithobius tricuspis (Lamb Leer Cavern) and Necrophlaeophagus longicornis (Elm Cave). 

The Pauropoda are tiny, blind creatures similar in shape to centipedes that are generally found in soil feeding on dead plant matter.  Although there are no records from Mendip caves there are cave records from elsewhere in the country and they might be found in accumulations of detritus in the threshold zone. 

The Symphyla are slightly larger centipede-like white organisms that also live on dead plant matter in soil.  Scutigerella causeyae has been recorded from Fairy Cave.  Although there are currently no Mendip cave records, Symphylella isabellae can be found in caves, sometimes far into the dark zone and has been recorded elsewhere in the country. 

Millipedes are more common with a number of cavernicole species, some of which are blind. Millipedes feed on plant debris including wood and are particularly common in oak woodlands on limestone, living for several years. Cave forms often have a thinner shell and more sensory bristles than those on the surface.   The three species most frequently recorded in Mendip caves are Blaniulus guttulatus, Brachydesmus superus and Nanogona polydesmoides (formerly Polymicrodon polydesmoides), which occur in the dark zone and can be considered cavernicolous. Several other species have been recorded, including members of the families Glomeridae, Brachychaeteumidae, Polydesmidae, Blaniulidae and Iulidae.

The Spotted Snake Millipede (Blaniulus guttulatus) in Fairy Cave