Clubionidae

Sac spiders

ARACHNIDA > ARANEAE > Clubionidae

The Clubionidae family includes 22 species in two genera, Clubiona (20), and Porrhoclubiona (2) where both species are rare, as are quite a few of the Clubiona. In fact, looking at the distribution maps, I believe there are only around a dozen that could realistically be encountered locally.

The term 'sac spider' comes from the compact silk retreat that they build each morning before coming active. They occur in various habitats, but are often found in foliage, which has resulted in a regularly used alternative collective common name of 'foliage spiders'.

They have a reasonably distinctive body shape with prominent spinnerets, but are generally rather plain with non-descript markings. Most are described as brown or greyish-brown with a mousy appearance.

Clubiona comta and Clubiona corticalis are very similar, but can usually be distinguished from their colouration and presence of an abdominal median band and chevon-like patterning. The two individuals featured below are confirmed as Clubiona comta - the first is an adult male, which is much darker than the female I found in the winter on our garden waste bin.

The remaining species cannot be reliably identified from photos as appearance, colour, depth of markings and other features are extremely variable and highly subjective. That said, there are a few features that when coupled with habitat and other factors, such as the month seen, may suggest a 'likely' candidate.

Clubiona neglecta is a local species with scattered distribution, often occurring in thinly vegetated, open habitats such as short grasslands. It is very similar to the following described species Clubiona terrestris, but with a darker head area and reddish-brown abdomen with a slightly darker, but often rather vague, cardiac stripe. The general colouration and the dark cardiac mark together with the habitat, and even the time of year, make Clubiona neglecta a 'likely' candidate.

Clubiona terrestris is a common and widespread species across central and southern counties, but decreasingly so further north. They occur in a variety of habitats, but notably in gardens and around buildings. The carapace is described as being light yellowish-brown with dark chelicerae, and the abdomen paler than in other species, varying from yellow to reddish-brown. The individual that I found in our garden was considered a possible Clubiona terrestris by one of the experts on the British Spiders Identification Group.

Clubiona lutescens is very similar to both C.neglecta and C.terrestris and is another to be considered.

Whilst all of the above could be found in a variety of habitats, many of the other species that I haven't specifically mentioned have more defined associations: Clubiona reclusa (abundant; preference for damp, marshy areas, but also occurs on heathland), C.trivialis (possible on local heathland), C.diversa (common on chalk grassland), C.brevipes (common; favours oaks where it can be abundant), C.pharagmitis and to a degree C.subtilis (wetlands).