Black widows spiders are notorious for their powerful venom and gruesome mating habits, which sometimes involves the females killing and eating the males after procreating.
There are 31 species of these spiders, which all belong to the genus (group of species) Latrodectus, data from the Integrated Taxonomic Information System (ITIS) shows.
Black widows are found around the world in temperate regions, including parts of the United States, Europe, Asia, South America, Australia and Africa.
They live solitary lives until the mating season comes around and it is time to pair up with a member of the opposite sex.
The spiders are named after the predilection of the females for killing their male counterparts after mating. The females often eat the males after killing them, with scientists speculating that this act provides them with a source of protein.
In the wild, black widows can live for up to three years, although the males tend to have much shorter lives as a result of this bizarre mating behavior.
Adult female black widows measure around half an inch in length and are usually more than double the size of the males of their species, although they can sometimes be up to 20 times larger, according to a report entitled “Black Widow Spider Toxicity” published this year by scientists from The Brooklyn Hospital Center and St. Luke’s University Health Network.
The females can be easily identified by their shiny black bodies and the characteristic hourglass-shaped mark located on the lower side of the abdomen, which can range in color from yellowish orange to red, according to the U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA).
Males can be grey or black in color and feature red or pink spots on the upper side of the abdomen.
Only the female spiders pose a risk to humans, with venom that is thought to be around 15 times more potent than that of a rattlesnake. Indeed, black widows are considered to be the most venomous spiders in North America.
But despite the popular perception, black widow bites are rarely fatal. In the United States, around 2,600 black widow bites on humans are reported every year, with only 1.4 percent of these cases experiencing severe symptoms, data from the Black Widow Spider Toxicity report shows.
While they are rarely fatal, a bite from these spiders can still be a painful experience. The venom can cause strong muscle pain, nausea, profuse perspiration, increased blood pressure, fever and mild paralysis of the diaphragm, which can make it difficult to breathe.
Pain from the bite can persist for between eight to 12 hours, while some symptoms may last for several days—although most people make a full recovery.
Those most at risk from black widow bites are small children, the elderly or people who are very sick.