Widow spiders are notorious around the world and there are 31 related species which all belong to the genus Latrodectus. They go by other names as well including button spiders in Africa and the redback spider in Australia.

black widow
Black widow in my shed, Nov 2017

Identification

This group of spiders has a few notable physical and behavioral characteristics that make them fairly easy to identify. One of the most distinctive is the hourglass-shaped design on the underside of the abdomen, which typically ranges from yellow to red. The majority of the spider is brown or black depending on the species and sex. The abdomen is large and round, and the legs are long, thin, and tend to be striped or banded especially if the spider is more brown than black. Females are larger than males and tend to be darker. Widow spiders often hang upside-down in the center of their web and are most active around dusk and at night. They can be found in and around living spaces, often in garages, basements, gardens, and other areas which attract their main food source – insects.

There is a closely related genus of spiders called Steatoda, and some species in this genus are known as the false widows. They resemble widow spiders but are less dangerous and markings are distinguishable, such as having the markings only on the back instead of the underside, or lacking the markings altogether.

Notable Species

Among the infamous black widows there are three species in North America – southern, western, and northern black widows. Six species that are found in Africa are commonly known as button spiders and include the brown button spider or brown widow which can be found across five continents. Australia is the home of the redback spider which has markings on both the back and the underside of its abdomen. The Mediterranean black widow has thirteen spots on its body, making it more unique-looking among these spiders.

Are They Dangerous?

If you are a male widow spider then the answer is definitely “yes.” The name widow comes from the mating ritual which quite often ends in the male being eaten by the female. Not only is this a bit intimidating for a male widow spider, but it also gives these creatures a serious reputation among humans.

As far as risks posed to humans, well, that can also be a yes. According to the National Geographic, “[a black widow’s] venom is reported to be 15 times stronger than a rattlesnake’s.” Antivenom has been created for many species, but according to some sources, the antivenom for the redback spider was shown to be no more effective than a placebo and also has dangerous side effects, limiting its use to only very serious cases.

It is important to note, however, that their reputation for being deadly is somewhat misleading. Most people who are bitten by a widow spider recover within 24 hours, or up to a week, and are left with no serious damage. Those most at risk for more intense reactions are young children, the elderly, and people who have reduced immune systems due to other conditions. These spiders are not particularly aggressive; bites result out of self-defense when the web is disturbed or when they feel threatened.

Bites from male spiders are usually not serious because the males produce a more diluted venom for hunting purposes and due to their smaller size their mouthparts are often physically unable to inject venom into a human. A female’s bite can contain more venom, but may also be a warning bite and contain none at all.

Risks to Widow Spiders

There has been research to suggest that a recently established population of brown widow spiders in Southern California is beginning to take over the territory of black widows in the area, which may be beneficial to humans as brown widow bites are not considered as serious. In general, the risks for these spiders is mainly down to natural predators like mud daubers and other spiders. Seeing as they commonly take up residence in and around human populations, there is no threat of habitat loss in the near future!

One thought on “creatuREport: Widow Spiders

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