We have rehomed a black widow spider after a member of the public found it in a car part that they had imported from America. The female black widow settled into her new home quickly and promptly laid an egg sac containing over 100 eggs. The baby spiders, known as spiderlings, have since hatched and can now be seen in the Animal Barn in Encounter Village.

The black widow spider is considered the most venomous spider in North America. Although females only measure 35mm long, their venom is extremely potent: it’s believed that it is 15 times as toxic as that of the rattlesnake. The spider gets its name because, unlike many spider species, the females may eat the males after mating to provide them with extra nourisment for egg-laying.

A female black widow spider can produce four to nine egg sacs during the summer months, each containing about 100-400 eggs. However, only a small percentage of these will survive to become adults themselves, due to several factors including predation and cannibalism. The eggs take on average 30 days to hatch and the female will usually guard them during the incubation time. The females mature in about 90 days and can live for up to five years, whilst a male's lifespan is much shorter.

Deaths in healthy adults from black widow spider bites are relatively rare in terms of the number of bites per thousand people. Sixty-three deaths were reported in the United States between 1950 and 1959. (source: wikipedia.com). No one in the United States has died from a black widow spider bite in over 10 years. Very often the black widow will not inject any venom into the bite and no serious symptoms develop (source: California Poison Control System).

Geoff Read, Section Manager for our Lower Vertebrate and Invertebrate department is taking no risks with his new arrival. The female and spiderlings are being kept in a secure case within a locked glass enclosure which also contains anti-venom. “Black widow spiders have to be carefully looked after, females especially so as they are more aggressive than the males”. The female and spiderlings are being kept in a secure enclosure alongside an old sample of anti-venin. As the valid vial of anti-venin needs to be kept cool it is kept in a fridge on-site.

The black widow spider is often confused with the false black widow spiders, which were introduced to the UK over 30 years ago from Europe. False widow spiders belong to the genus, or group, called Steatoda and there are currently six or more species of false black widow spiders that live in the UK.

Images on this page are of the black widow spider and spiderlings living at Marwell

28 January 2009

Sign up for our newsletter to keep up to date with our latest projects.