Monday 12 October 2015

Clubionidae: Sac spiders

The Clubionidae has 24 British species, mainly in the genus Clubiona. They are small to medium spiders usually of plain brownish colours, often with dark chelicers, and silky appearance. They have eight round eyes of similar size. Spinners are long, but converging, protruding from the end of the abdomen. They hunt mainly at night, without the help of a web, and spend the day in tightly woven silk cells they weave under stones, between leaves or in loose bark in trees and bushes. Species are difficult to identify in the field.

Egg sacs
The spiders mature in spring and summer and courtship is not very elaborate. Mating sometimes happens on the female's retreat. Females will also lay eggs within the retreat, where they guards their clutch and later, the spiderlings. Some species fold up or curl a leaf and lay their eggs in the fold, which the female then closes with white silk, with her staying inside.
Clubiona corticalis
Male Clubiona sp.
Female Clubiona in cell with spiderlings.
Male Clubiona sp. inside his cell between a window pane and leaf.
Clubiona with the chewed remains of her spider prey Amaurobius.

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