The bites , although not life-threatening, are nasty as the venom of these spiders is cytotoxic. Cheiracanthium fulcatum Griswoldia sp. Both spiders are small, about 10mm in length and have a similar body shape, straw colour and make similar silk sac retreats, hence the common name of sac spider. The legs and cephalothorax are similarly coloured but sometimes the cephalothorax and legs might be slightly darker . However , Clubiona has a brown to maroon face and chelicerae and the first and fourth pairs of legs are a similar size and Cheiracanthium, on the other hand, has a black face and chelicerae and the first pair of legs is noticeably longer than the fourth pair and these they use for detecting and capturing their prey.
Sac spiders are fast and aggressive, free ranging and nocturnal and commonly occur on vegetation.
They are important in controlling agricultural insect pests. I have, on more than one occasion found a sac spider gazing up at me from a bunch of grapes in the local large supermarket. They construct a silk-like retreat in a curled leaf or in the heads of Protea flowers. With the onset of summer they find houses an ideal habitat, constructing their sac retreats in the folds of curtains, bedding, clothing, doorframes and corners. Being active at night, it is then that most bites occur when the animal is inadvertently pressed against the body, as the large fangs of this spider are capable of penetrating light fabrics.