For the 2012 spider of the year there are a number of ‘firsts’: a new spider family (Tetragnathidae – long-jawed spiders), a new habitat (caves) and a new joint animal of the year (its also cave animal of the year). But one thing after another; to begin with, a brief introduction to the spider of the year: Meta menardi (Latreille, 1804) the large cave spider.

Photo: Heiko Bellmann

[Gallery]

The large cave spider is one of 955 species of long-jawed spider known throughout the world. In Europe we have 29 species, in central Europe 19.

The large cave spider Meta menardi is geographically widely distributed. It occurs in subterranean cavities throughout the Palaearctic region, with the exception of Japan. In central Europe it is usually found in upland regions, and is particularly common in karst areas such as the Frankish or Swabian Alps. The spider lives in subterranean caves, cellars, mineshafts and within stone runs with a medium level of humidity and a constant temperature above 7°C. Caves with high humidity or through drafts are avoided.

The body length of the large cave spider Meta menardi is 11 to 13 mm in males and 14 to 17 mm in females. Colouration is generally quite dark; the cephalothorax is red–brown, the abdomen pale or dark brown, both with black markings. Two large spots are often visible. The legs are brown with black rings. There is a chance to mistake it for the small cave spider Metellina merianae (Scopoli, 1763). This is smaller and its colouration more grey. Nevertheless the second species builds larger webs (with more radial lines and catching threads) and is thus able to add strongly flying insects to its food preferences.
Meta bourneti Simon, 1922 is, by contrast, just as large as M. menardi and also similarly coloured, but is only known in isolated occurrences from the Rhineland-Palatinate.

In addition to these conspicuous species, subterranean caverns have a diversity of further spiders; a number of which show clear adaptations to life underground. These spiders are, except for M. bourneti (see above) usually much smaller then the Meta species mentioned above and thus cannot be confused with them.

Mating in these Meta spiders generally takes place in early summer. Following this, from mid July to early August, the female builds a 2 to 3 cm diameter cocoon which hangs from a thread. The cocoon contains about 200 to 300 eggs, which the female watches over for two to three months until her death. Around the end of August the egg sac begins to disintegrate and the young spiders are visible in the cocoon as small black spots. The young spiders will not actually leave the cocoon until next spring. The offspring then make their way to the cave entrance, where they can be encountered over a number of days to weeks. Some of the young travel from here into other cave systems; the rest remain in the cave of their birth. In this way the population is both distributed and maintained. The large cave spider Meta menardi reaches an age of 2 to 3 years, in contrast to most of our native spiders which only live for a year.

The 20 to 30 cm web of the large cave spider can be interpreted as highly rudimentary (i.e. an orb web with an open centre) and is rarely used to catch prey. Meta menardi tends to spend much of its time near the cave wall where it can catch woodlice, beetles, centipedes, millipedes, overwintering butterflies and moths and other small animals; occasionally even snails. Typically these are hung from the web on small threads. This hunting behaviour, without reliance on the web – which was originally used to catch prey – can be seen as an adaptation of these animals’ behavioural genetics to life in caves.

The large cave spider Meta menardi is also called the cave orb-weaver, even though it doesn’t belong, like garden spiders, to the orb-weaving family, but rather to the long-jawed spiders instead. Because of its large size it is one of the most conspicuous cave animals in the temperate zone. These animals live all year round in caves, mine shafts and cellars cut into natural rock. Consequently, this spider species has also been elected ‘cave animal of the year 2012’. The spider thus represents a larger number of animals who depend on protected and frost-free retreats associated with mines. The society of German cave and karst researchers wish to show, through choosing this spider, that there is still much to be done in the study of subterranean ecosystems, and the animals which occur here (see also http://www.hoehlentier.de).

Together with its election as cave animal of the year, the large cave spider Meta menardi has also been chosen as the ’European spider of the year 2012’. This supports the excellent cooperation between cave biologists and specialists for those animal groups living in caves. The spider researchers (arachnologists) are reliant on the local knowledge and expertise of the cave researchers (speleologists), in order to learn more about the species found in underground habitats.

Keep your eyes open next time you visit a cave: the large cave spider is somewhere nearby!

Christoph Hörweg