Black widow spiders are one of the most feared and dangerous species in the world, for the simple fact that they have a potent and toxic venom and that they are often found in the same areas that people inhabit. But past the fact that they are dangerous, many people don't tend to know much else about black widows, or for that matter what to do if they happen to find one.
One of the most important facts about black widows that most people don't tend to know is that there are actually several distinct species, and that black widow is actually only the common name for them all. There are in fact six species in the family, although the three most common are the southern black widow (Latrodectus mactans), northern black widow (Latrodectus variolus), and the western black widow (Latrodectus hesperus). However all three species are very similar in most respects, and the differences between them aren't easy to tell from a chance encounter.
The black widows tend to spend most of their time hanging upside down in their webs, which are usually a mess of tangled fibers. Unlike many other spiders, their webs rarely have a recognizable shape, and instead are simply made according to the surrounding surfaces. The silk of black widows is very strong, and their webs are rough and sticky, having an almost fuzzy texture to them.
The prey of the black widows is generally smaller insects and flies, although anything that enters its web is liable to be bitten. Due to the potency of the venom black widows have occasionally been known to kill much larger prey than themselves, although this is not common. The fact that the venom takes a few minutes at least to take effect, larger things that disturb the web are often able to escape, only to die a short time afterwords. The prey that the spider does eat is often held by the spider until the venom takes effect, although often entanglement in the web is also a factor in this.
Despite its fearsome reputation, the black widow has several natural predators f its own. There are several species of predatory wasp that tend to prey on black widows as a preference, as well as larger spiders and occasionally things such as scorpions or centipedes. Also in some cases if the web of a black widow is too near to the ground then it may be torn apart by overwhelming numbers of ants, although this is the case for almost all invertebrates.
As well as direct predators, competition may reduce the numbers of black widows indirectly in some locations. Larger species of spider that build bigger webs, are more active and that share the same habitat as black widows can often mean that they will struggle to find a niche. Also areas becoming more frequently used or more brightly lit tend to discourage black widows from inhabiting them.
The venom of the black widow is known to be one of the most toxic in the world of any creature, although fortunately they do not produce very much of it. Also their mouth parts are often not powerful enough to pierce through tougher areas of the skin. It is because of this that there are relatively few deaths from black widow bites compared to the number of people bitten. Certainly if the spiders were able to inject more venom into their bites, many more people would die from the venom.
Despite the potency of the venom, most black widow bites are not fatal to a fully healthy adult, although the symptoms of the bite are painful and can take time to heal. Children, the elderly and those with an existing medical condition however are more at risk, and bites can tend to prove fatal in many more of these cases. Thankfully however, the reported number of bites has decreased greatly over the last thirty years, due to a number of factors.
One of the largest sources of bites and encounters from black widows was when people more commonly had outside toilets. These would be dark most of the time, as well as sheltered and attractive to their prey species. However as most people tend to have indoor toilets these days, which are lit and used more of the time, bites have dropped significantly.
Generally speaking black widows are more dangerous when you don't know you have some in the home then if you do. Bites are most common when someone has blundered into the web and thus threatening the spider. However if you know that you have a web somewhere in your home, and you do not disturb it, then the black widow can be useful in removing pests. The fact is that black widows will tend to never leave their web site once they have established it and have a steady source of food, meaning avoiding them is easy.