About Clubiona corticalis (Walckenaer, 1802)
Clubiona corticalis, commonly known as the bark sac spider, is a species of spider in the family Clubionidae. This species can be found across most of Europe and in Central Asia. Adult males of the species reach 6–10 millimetres (0.24–0.39 inches) in body length, while adult females are 7–10 millimetres (0.28–0.39 inches) long. The prosoma (front body segment) and legs are glossy reddish-brown or light brown, but the jaws (chelicerae) are much darker. The abdomen (opisthosoma) is brown or dark brown, with distinct leaf-shaped central markings against a lighter background. The two sexes are very similar in appearance, with only males having a more slender abdomen. Sexually mature individuals can be found from April to September, inhabiting coniferous forests. They most often live under loose bark of dead trees, which is the origin of the species' Latin name corticalis, meaning 'of cortex'. Less frequently, they occur under stones, and they may sometimes be found inside human houses. Females lay their eggs in early summer, and guard the eggs until they hatch. Most of these spiders die at the end of summer, with only a small number overwintering in their nests until the following spring.
