South Africa is home to a large number and diversity of spiders, with well over 2 000 species recorded, the vast majority of which are completely harmless to humans. This month we will take a closer look at the sac spiders of the genus Cheiracanthium.
Sac spiders are small to medium sized spiders that can measure up to 25mm across. They are characterized by their very dark, almost black mouth parts, the body and legs maybe brown, creamy white or pale yellow in colouration. The abdomen may also be a pale green colour in some specimens.
They are free ranging or free-living spiders and as such do not build a web to capture prey. They are nocturnal and actively move around hunting their prey. The common name is derived from the silk sac which they construct to function as a place to shelter or a place to lay their eggs. These silk sacs are frequently found in the folds of curtains. Their range extends throughout much of South Africa, only being absent from parts of the dryer western regions of the country. They are one of our more prolific spider species and are often found in and around buildings as well as in suburban gardens.
Studies have shown that sac spiders are equipped with cytotoxic venoms and a number of species are considered to be medically significant. Bites are however generally mild in nature; an itchy welt will typically form at the bite site. Other symptoms may include localized pain, swelling and redness that should resolve in a few days. In some cases, a necrotic wound may develop however reports of severe necrotic lesions forming as a direct result of sac spider venom are largely unfounded and are mostly likely due to a secondary infection.
It is important to note that in reality it is impossible to accurately diagnose a spider bite unless the offending spider is seen biting the victim or the bite is felt, and the spider found in the immediate vicinity. The spider also needs to be correctly identified by an expert to determine if it was in fact a medically significant species that was responsible for the bite.
Due to the fact that they are free ranging spiders they do occasionally find their way into clothing and bedding. Most bites occur when the spider is accidently squashed against the skin. Shaking out clothing and bedding will greatly reduce your risk of a bite. Although sac spiders have relatively large fangs it is not easy for them to actually penetrate human skin.
For more information on venomous animals, awareness training and talks, as well as a professional 24hrs problem snake rescue service, contact the author at Wildlife Safety Solutions: 073 934 6156; info@wildlifesafetysolutions.co.za; www.wildlifesafetysolutions.co.za, FB Wildlife Safety Solutions, Instagram wildlife_safety_solutions
