Facts that break myths about black widow spiders

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Black widow (probably Latrodectus mactans Where Latrodectus hesperus). The delicate footsteps of a spider do not hinder the petals of the rose. Credit: Wikimedia Commons.

Black widows are perhaps the most famous spiders in the world. But as is often the case with celebrities, myths and rumors outweigh the real facts in the public consciousness. Let’s look

The black widow’s venom is very strong, but its bite is not really that dangerous

Did you know that the venom of a black widow is about 15 times more potent than that of a rattlesnake? Ouch! However, they are also over 1000 times smaller and, moreover, the black widow does not release all of its venom at once. Remember, the dose makes the poison.

When a black widow bites a human, neurotoxins in the venom can cause pain, swelling around the wound, cramps, sweating, and chills. These are quite unpleasant symptoms, but they are not as worrisome as some people think. Black widow venom is intended to neutralize small prey like insects, not kill large predators like humans.

Each year, thousands of people are bitten by a black widow in the United States, mainly in the southern and western parts of the country where spiders thrive. Less than 1% of these cases resulted in severe symptoms. When severe symptoms occur, most hospitals now have an antivenom that neutralizes neurotoxins.

Black widows are sometimes called the deadliest spiders in the world, but that’s not true at all. Although deaths can occur, usually in young children, the elderly or the infirm, they are extremely rare. Many years can go by without a black widow-related death. The deadliest spider in the world is actually the male Sydney funnel web spider, Robust Atrax, which can be found (of course) in Australia.

Black widows almost never bite people without provocation. Spiders bite in self-defense when they feel threatened, usually when someone accidentally walks or sits on them. Black widows like to hunt in vines, outhouses, and other shelters where debris collects, so it’s best to be extra careful in these settings. According to a 2014 study, people are at the greatest risk of getting bitten by a black widow when it is squeezed or pinched.

Females have a reputation for being man-eaters, but that’s a myth

In popular culture, women who kill their husbands are sometimes referred to as “black widows,” referring to the idea that these female spiders devour males after mating. However, it is a myth (with just a grain of truth).

Research showed that female red spiders, which are closely related to black widows, eat their mates after copulation only about 2% of the time.

The idea that black widows eat their mates can be traced to laboratory experiments in which only one male and one female were trapped in the same pen. Black widows are up to 150 times the size of men and can therefore also be hungrier. Having nowhere to escape, the males are of course at enormous risk of being cannibalized. But in the wild, males have many opportunities to escape.

“To understand the facts about black widow mating, you must first understand that there are many different species in the world in the group of black widows (genus Latrodectus), and three different species of black widows in the United States alone, two in the east and one in the west (not counting brown and red widows). These species do not all behave in the same way. In addition, in the past, most mating observations have taken place in laboratory cages, where males could not escape, ”biologists affiliated with the Burke Museum written in a blog post.

“The only one known Latrodectus species in which partner cannibalism in the wild is the rule, not the exception, are found in the southern hemisphere. Among American species, partner cannibalism sometimes occurs in Latrodectus mactans, the eastern (southern) black widow, but most males survive to mate another day. In the other two black species, including the western black widow L. hesperus (the only species west of Kansas), partner cannibalism has never been observed in the wild! They added.

Their offspring is another matter, however. All young black widow spiders start out as cannibals

When properly fed, black widow spiders weave large webs to trap prey, such as flies, mosquitoes, beetles, and even caterpillars. Females also use the web to hang a cocoon containing hundreds of eggs. But when they hatch, these young people are not exactly filled with brotherly love.

Jonathan Pruitt, an assistant professor who studies spiders at the University of California, Santa Barbara, noticed that all of these eggs were exactly the same size and that the spiders hatch and molt around the same time. He found it strange and in a study published in 2016, Pruitt and other biologists conducted an experiment in which they varied the rate of development of spider eggs by adjusting the temperature. When the spiders hatched to different sizes and got mixed up, it didn’t take more than a few days for the larger newborn to devour all of its little siblings.

Spider moms would like to avoid this outcome as much as possible, as having only one surviving offspring out of the hundreds that initially hatched is an evolutionary disaster. This is why female black widows have developed ways to supply their eggs very precisely so that the spiders develop at the same rate.

Black Widow’s combed limbs give her “spider senses”

Black widow and her prey. Credit: Wikimedia Commons.

Black widows wove their irregular funnel-shaped webs using her pair of combed hind legs. The tiny hairs covering the long limbs also allow the spiders to cover and trap their prey in silk once the unsuspecting victim is mad enough to approach the widow’s web. Speaking of canvases, strands of silk also extend the widow’s senses. Once a fly lightly touches the web, vibrations are sent along the string, which can be detected by organs located on the joints of their legs.

Like their relatives, black widow spiders produce bristles with exceptional material properties, including strength comparable to that of steel. In 2018, researchers from Northwestern University find that spiders use a complex and hierarchical process of protein assembly to produce their hyper-resistant silk. If the method can be emulated, scientists believe we could make synthetic materials resembling spider silk that could be used in high-performance textiles, cable bridges and other constructions, replacements for plastic. and biomedical applications.

Only females have the iconic red hourglass

Credit: Wikimedia Commons.

While they are juvenile, black widows are colored brown and white and only acquire their characteristic charcoal color once they molt and reach adulthood. Adult females, but not males, also develop a red hourglass mark on their abdomen, as well as a few red spots on the spinnerets (the silk-spinning organs of a spider) and along the mid-back. Scientists believe the red coloring helps females, who are much larger than males and therefore easier to spot, ward off predators. In the animal kingdom, the red marks send a clear message “stay away, I am dangerous”.

Black widows are replaced by brown windows in some places

The brown widow spider (Geometric Latrodectus Koch) looks like the black widow, however, the hourglass of the brown widow is yellowish orange or reddish orange instead of the bright red like in the black widow. They are relatively new to North America, with the first documented sighting of a brown widow spider occurring in 1935 in Florida. Over the past decade, the researchers found that the range of the brown widow spider has rapidly expanded, particularly in California. They are so successful that they have started to move the native black widow spiders around.

Males do not bite, however, the female brown widow is poisonous and injects neurotoxic venom when she bites. However, the venom is much less potent than that of a black widow, so owners can rejoice.

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