SPIDERS: HISTORY, CHARACTERISTCS, SILK, WEBS

SPIDERS

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Spider are arthropods with eight legs and sensory hairs on their bodies. All spiders produce silk, but only about half of spiders spin webs. Almost all are venomous though the majority of species have venom too weak to harm humans and their fangs generally can not pierce human skin. They are found almost everywhere: rain forests, deserts, houses, even 100,000 feet in the sky, drifting in the wind from thread-like "parachutes” and floating in the open sea.

Most spiders can be split into two broad groups: 1) araneomorphs (also known as 'true spiders'), a group that includes 90 percent of spiders on earth; and 2) mygalomorphs. Tarantulas are mygalomorphs, which are considered more primitive than true spiders. This means that they have evolved less since ancient times, and have therefore maintained certain features that true spiders have since shed — such as downward-pointed fangs, and their large size. [Source: Emma Bryce, Live Science, August 4, 2023]

There are over known 111,000 species of Arachnids, which includes ticks, mites and scorpions as well as spiders. There are more than 50,000 known species of spiders in the world, of which only a few can harm humans. Altogether there are perhaps 150,000 different species of spider as many have not been described or identified.

Certain spiders drift about on homespun balloons. David Attenborough said different spiders have different personalities. When spiders of the Salticidae family are confined to a maze and shown a prey animal, they will reach it even when doing so initially requires moving in the opposite direction.

Websites and Resources: Arachnology Homepage with Lists of Resources arachnology.be/Arachnology ; Spider Identification Chart U.S. Spiders termite.com/spider-identification ; Spiderz Rule spiderzrule.com ; BugGuide bugguide.net ; Amateur Entomologists' Society amentsoc.org ; MDPI Insects mdpi.com/journal/insects; National Geographic on Bugs National Geographic ; Smithsonian bug info si.edu/Encyclopedia_SI/nmnh/buginfo Safrinet Manual for Entomology and Arachnology SPC web.archive.org

Websites and Resources on Animals: Animal Diversity Web animaldiversity.org ; BBC Earth bbcearth.com; A-Z-Animals.com a-z-animals.com; Live Science Animals livescience.com; Animal Info animalinfo.org ; Encyclopedia of Life eol.org , a project to create an online reference source for every species; World Wildlife Fund (WWF) worldwildlife.org the world’s largest independent conservation body; National Geographic National Geographic ; ; Endangered Animals (IUCN Red List of Threatened Species) iucnredlist.org ; Biodiversity Heritage Library biodiversitylibrary.org

History of Spiders

The first spiders walked the earth about 400 million years ago. They are more closely related to scorpions and horseshoe crabs than insects. In the early days they used silk mainly to construct hiding places.

In 2019, scientists from the Royal Ontario Museum in Toronto announced that a 500-million-year-old, thumb-sized, sea-dwelling predator found in the Burgess Shale of British Columbia in Canada was ancestor of spiders and scorpions. The creature — named Mollisonia plenovenatrix — had two bulgy egg-shaped eyes, a dorsal skeleton that resembles a shield and numerous pairs of limbs that could grasp, crush and chew. [Source: Kelda Yuen, CBC News September 12, 2019]

a Mollisonia

Kelda Yuen of CBC News wrote: It was a pair of fang-like appendages at the front of the creature's mouth that most excited ROM paleontologist Jean-Bernard Caron, whose findings were published Wednesday in the science journal Nature. The appendages, called chelicerae, meant the species was a member of the family Chelicerate. Not only that, it was that family's oldest known ancestor, at about 506 million years old. "Chelicerate is a group that is familiar with everybody because it includes spiders, scorpions and horseshoe crabs. Those represent 115,000 species of animals today. And they are part of an even bigger group called arthropods which are defined by a jointed body and limbs," said Caron. But while they are one of the largest groups of species, Caron said "their origin has always been puzzling to scientists."

Web weaving is thought to have evolved around 135 million years ago in the Cretaceous period when dinosaurs roamed the earth. A segment of spider web preserved in a 110-million-year-old piece of amber shows that spiders were weaving perfect orb-style webs way back then, earlier than previously thought. The amber sample contained 26 web strands grasping a mite, a fly, a wasp leg and a beetle as well as drops of web glue. Enough clues have been found on the web threads to show they were part of a classic orb web made of concentric circles joined by radiating "spokes."

Scorpions, Centipedes and Spiders

Scorpions and spiders are members of the Arachnid class of animals. They have eight legs and a hard exoskeleton and molt like insects. When molting a growing spider casts off its exoskeleton. This is a dangerous time for spiders because molting requires a lot of energy and without their their exoskeleton the spider vulnerable to predators. Many species of spidersare carnivores that feed primarily on insects. Many produce poisons and have hair on their legs that can detect sounds, sensation, objects and even taste.

Members of the Arachnid class of animals emerged about 400 million years ago and are more closely related to horseshoe crabs than insects. Insects have three pairs of legs, spiders and scorpions have four, crabs and shrimps have five and centipedes and millipedes have many.

Insects, centipedes, millipedes, arachnids (including spiders and scorpions) and crustaceans belong to the phylum of arthropods. Arthropods account for three fourths of all known animals. All have exoskeletons made of chitin; a body divided into segments and protected by cuticle; jointed legs arranged in pairs; an open circulatory system with organs bathed in a liquid called hemolymph that is pumped around the body by the heart; and a nervous system comprised of paired nerve chords.

Largest, Longest and Smallest Spiders

The smallest spiders in the world come from the family Symphytognathidae. According to Guinness World Record the smallest Patu digua spider was recorded at 0.014 inches, while the Samoan moss spider can be as small as 0.011 inches long. [Source: Olivia Munson, USA TODAY, February 26, 2023]

The giant huntsman spider (Heteropoda maxima) is the world's largest spiders based on leg span. It measures 30 centimeters (11.8 inches) across. [Source: Emma Bryce, Live Science, August 4, 2023]

The goliath bird-eating spider (Theraphosa blondi) is the world’s largest tarantula and spider. Living in dense rainforest in northern South America, they have slightly shorter legs than the giant huntsman spider, but still reach 28 centimeters (11 inches) and they weigh more 175 grams (6.17 ounces). Its body measures 13 centimeters (5.1 inches) and they double the weight of the salmon pink tarantula, the next biggest tarantual. In 2014, an entomologist exploring the jungles of Guyana came across a goliath birdeater that was so big, it rustled the undergrowth and was equivalent in size to a young puppy. See Tarantulas [Source: Emma Bryce, Live Science, August 4, 2023]

giant huntsman spider

Top 10 biggest spiders, by leg span
Giant huntsman spider (30-centimeter, 11.8-inch leg span)
Goliath birdeater (28-centimeter, 11-inch leg span)
Brazilian salmon pink birdeater (25.5-centimeter, 10-inch leg span)
Brazilian giant tawny red tarantula (25.5-centimeter, 10-inch leg span)
Face-size tarantula (20.3-centimeter, 8-inch leg span)
Hercules baboon spider (20-centimeter, 7.9-inch leg span)
Colombian giant redleg tarantula (18-centimeter, 7-inch leg span)
Camel spider (15.2-centimeter, 6-inch leg span)
Brazilian wandering spider (15-centimeter, 5.9-inch leg span)
Cerbalus aravaensis (14-centimeter, 5.5-inch leg span)
[Source: According to a-z-animals.com, USA Today]

Spider Characteristics and Behavior

In addition to their eight legs, spiders have eight eyes and some species have four lungs. The fact they have lungs enables to reach large sizes than insects whose size is limited because they don’t have lungs (See Insects). Some, like wolf spiders and jumping spiders, have excellent eyes and hunt primarily by sight. But most spiders have very weak eyes are rely on their sense of touch and their sensory hairs to gain information about their environment..

Almost all species of spider are hairy, but their hair is not like human hair. Spider hair is actually part of the spider's body — extensions of the exoskeleton call senate. Some of the follicles are actually sense organs for touching, tasting, hearing, and are used for detecting prey or mates.

Hair follicles on their legs and abdomens are the most important sense organs for most spider species. Spider hairs resemble short, hollow pegs. They are moist inside and enable spiders to taste the surface they are touching. Tiny, ringed pits help them to smell prey, enemies and potential mates. Long hairs, extremely sensitive to air movement, alert spiders to — the merest twitch of a nearby insect." Water spiders are able to float on the water because their hair trap air. Some spiders have hairs that spiderlings cling when they ride on their mothers back.

Spiders are very solitary creatures. They don't socialize except at mating time and "don't express affection the way dogs and cats do." They spends most of their life hunting, eating, reproducing and escaping predators. Most of everything they do is genetically programmed and instinctual.

Some spiders masquerade as foul tasting ants to deter predators. Other are very good at playing dead. Some spiders can leap 25 times their body length to seize prey.

Feeding Spiders

Spiders eat about 15 percent of the body weight every day. They are mostly carnivores that feed on insects. Some eat larger prey such as small frogs. Spiders help humans by eating insects that attack crops. According to one calculation two million spiders can be fund on one acre of farmland and they consumer billions of insect a year.

jumping spider

Spiders don't necessarily need to eat all that often. Most species can go for a month or more without food and tarantulas can live as long as year. Female spiders are usually the most active hunters because they need more food to feed their young.

Spiders employ different hunting methods. Many use webs to catch prey. Many also use venom to paralyze but necessarily their prey. If a victim is too large the spider can immobilize it with layers of silk. Biting spiders sometimes paralyze prey with a bite to a certain nerve and then wrap it in silk and stored live until it can be consumed or given away as mating present. Some small spiders work as a group to catch large prey but this kind of behavior is rare.

All spiders are fluid feeders. They can not eat solid food. They digest their food externally by vomiting digestive juices onto their prey or injecting it with flesh-softening secretions and then suck up the liquified food using a strawlike appendage.

Jumping spiders often prey on mosquitos. Adults take about an hour and half to feed on a mosquito. Juveniles feed by attaching their fangs to the thorax of the mosquito and then draw blood from the insect’s abdomen.

Spiders are also feed on by many creatures such as birds, reptiles and large insects. Some species of wasp paralyze spiders and lay their eggs inside them. When eggs hatch, the larvae slowly eat the fresh tissue of the spider dies form being eaten alive. See Wasps

Spider Mating

A male spiders do not have a penis or similar devise to implant sperm directly into a female. Instead he spins a small silken napkin, deposits sperm on it from his genital pore, sucks the sperm into feeler-like organs on his head and squirts the sperm from these into the female's genital pore.

Females are often significantly larger than the males and often try to eat them. Males usually signal they female somehow they are not prey, deliver the sperm; and try to escape before the females eats them. Some males signal the female visually. Others send special rhythmic vibrations along their webs. Other present gifts of insects.

The males are wired by the instincts to mate and little else. Females on the other hand try to get as big and fat as they can so they as produce as many eggs as possible. Female spiders lay anywhere from 20 to 100 eggs. When the offspring they often ride on their mother’s back. As the young grow larger they shed there skins about a dozen times until the reach maturity.

According to Smithsonian magazine: Among some species, “male spiders raise their vibrant fan in the air and give the performance of a lifetime in hopes of, well, getting laid. The female spider will chase him and lunge at him, each time threatening death, until she is finally impressed with his routine (or kills him out of sheer disappointment.) This foreplay ritual can last up to 50 minutes. In the face of death, that’s one safety dance worth the effort. [Source: Katherine J. Wu , Rachael Lallensack, Smithsonianmag.com, February 14, 2020]

According to Discover magazine: One of nature’s most elaborate mating rituals belongs to the nursery web spider. Males wrap a collection of gifts — typically edible insects — in silk bundles and present them to potential mates. In some cases, male spiders try to sneak in worthless items like the leftovers of already-eaten bugs, so females have learned to examine the gift. Danish researchers found that far greater success was awarded to males who had a nicely wrapped package. [Source: Gregory Mone, Discover, June 22, 2012]

According to National Geographic: A female crab spider (Misumena vatia) feasts on a katydid as a much smaller male crab spider of another species (Thomisus onustus) perches on her abdomen. While it is common for a male crab spider to sit on a female before mating, scientists say it is rare to spot this among different species.

Black Widow Spider Mating

The black widow spider (Latrodectus Hesperus) can be identified by a red hourglass marking on it belly. Its venom is more potent that of a rattlesnake. Still death occurs at most to a few people a year in part because the amounts of venom the spider injects is relatively low. Black widows gets their name from the observation that males are killed and eaten by females shortly after mating. A female can live up to a year or more and produce several egg sacs containing up to 800 eggs, which hatch in about a week. Females usually stand guard over their eggs and may defensively attack those who threaten the offspring. [Source: Matt DiSanto, State College Centre Daily Times, October 25, 2023]

Contrary to the popular myth the larger female doesn't necessarily bite the head off the smaller male after mating. Like all species of spider, if hungry, females will sometimes eat their own kind. Mindy Weisberger wrote in Live Science: Black widow females are about twice as large as males, so the smaller suitors have to take some precautions when approaching a female's web, lest they be mistaken for prey and eaten before mating even gets underway. Males stay safe by announcing their presence to the female with vigorous rump shaking.

As a male steps onto a female's web, he vibrates his abdomen, sending signals coursing along the silk strands. He advances, vibrates and pauses, advances, vibrates and pauses — a pattern distinctly different from the shorter, more irregular movements of trapped prey, researchers found in a study, published in the journal Frontiers in Zoology. The study authors also discovered that the vibrations that males produce are at a low amplitude, further distinguishing them from prey movements, which were more dynamic and percussive. [Source: Mindy Weisberger, Live Science, February 14, 2023]

Spider Silk

Spider silk which is one of the most amazing and strongest materials on the face of the earth. Woven from "pleated protein sheets surrounded by springy coils of amino acids," it is twenty times stronger than steel yet more elastic than nylon and three times harder to break than Kevlar. It can be dry or sticky or as thin as a million of an inch and can absorb more energy before it breaks than any other material. The formula for spider silk was developed in the age of the dinosaurs and has remained virtually unchanged ever since. [Source: Richard Connif. National Geographic, August 2001]

Spider silk thread, which are generally about three to five micrometers across, are produced in the silk glands in the rear of the abdomen from a highly concentrated solution that is half water, half proteins. Most spiders have three pairs of showerhead-like spinnerets (stubby appendages that pull the silk out of the glands) that are covered it hundreds of silk-releasing spigots (external opening of the silk glands). Spiders cut the threads with sudden yanks from their back of the hind legs.

An individual spider can produce different kinds of silk that can emerge sticky, wooly, wet or dry. The spinnerets controls the thickness and texture by combing multiple strands into a single, solid thread. The silk which is squeezed out like toothpaste by special muscles and turns from liquid into thread not because it dries but because tension reorients the protein molecule from folded rod shapes to chains of linked logs.

Spider silk is biodegradable. It is made with water as a solvent rather than harsh organic chemicals. Its tensile strength is far superior to steel by weight and near as string ast steel by volume. But what makes it particularly strong is its elasticity. Kevlar stop bullets with strength, spider silk stops them by stretching.

One of these secrets behind the strength of spider silk is the fact that single thread is comprised of thousands of filaments each only a few nanometers across, too small to be seen in a regular microscope.. With some many strands if a few break so what. Interspersed with the filaments are fluid-filled channels that help disperse the force making one filament less likely to break. Another secret to the strength of spider silk is the way the proteins that make up the silk are bonded into longs chains and spun in a sophisticated way be spider’s spinnerets. The protein molecules line up in the direction of the flow and formed into liquid crystals, then stretched long and thin before the water removed to make it hard. Scientists have built and patented a device that mimics some of these processes.

Uses of Spider Silk

Each species of spider produces its own kind of silk. Some produce different silks for different purposes: building webs, making eggs sacs, lining nests, weaving tents for offspring and producing safety lines used in escapes. The toughest threads are often composed of dragline silk, which is used to make the framework of spider webs and to leap from houses or trees.

Some spiders spin silk to wrap their prey or keep their eggs safe. Other kinds of spiders make silk that can attract victims or warn off larger animals that might damage the web. Many of species of spiders hangs from a single strand of silk that is cemented at a surface at irregular intervals, in the same way a rock climber attaches his rope. The strand can be adjusted in midair if it is to short to absorb the fall.

The golden silk spider has seven pairs of glands that each produce a different kind of silk: one for wrapping prey, another from wrapping the spider’s eggs, two kinds of sticky capture silk used to make the circles on a web.

Bola spiders hurl weighted single filaments at its prey like a lasso or bola. Some spiders lasso passing insects with a sticky droplet at the end of a silken thread. The scaffold spider constructs a traps that snags its victim with glue and hoists its into the air. Others climb to high perch and send out strand of silk that is picked up the wind and carried up 100,000 feet in the air and 200 miles overland. Some birds steal spider silk and use it in the construction of their nests.

Spider Webs

Classic orb webs are comprised of: 1) a spoke-like framework made of strong dry threads a few thousands of a millimeter thick; and 2) a spiral that looks like concentric circles made of thinner, highly elastic, glue-covered silk for trapping prey. The web must be string enough to hold prey and support the weight of the spider; elastic enough to flex in the wind or when a flying insect hits it; and springy enough to bounce back before the sticky threads become a tangle of goo.

Some spiders use 600 spinning nozzles, which can weave seven different kind of silk into highly resilient configurations. Web building is genetically programmed and not learned, with each species making its own unique pattern. About a third of all spider make orb webs. Another third weave sheet webs, cobwebs and other kinds of webs. A typical orb web takes about an hour and half to make and requires 100 feet of silk. Webs rarely remain intact for more than 24 hours. Some spiders make webs and reweave them up to five times a day.

Most spider webs are spun by females. Males usually give up the practice when they reach maturity in part because they don’t much food. Females need the food that webs provide so they can make eggs. Orb webs are usually spun in flyways with the aim of catching flying insects. The first threads to be laid down are a dryline made in the shape of a star that act like scaffolding. After the spider makes the frame and “spokes” then an auxiliary spiral and finally a spiral of sticky threads is produces.

In a study on how drugs affect the mind certain illegal drugs were injected into spiders to see how their webs would turn out. When the spider was given "speed" the web was tangled and irregular. With tranquilizers and marijuana the webs were smaller. Under the influence of LSD the web was more symmetrical.

Interesting and Diverse Spiders

Jason Bittel wrote in National Geographic: Spiders are remarkably diverse. There are more than 50,000 known species, including diving bell spiders that live mostly underwater, arctic wolf spiders that can thrive north of the Arctic Circle, and giant spiny trapdoor spiders that can reach the ripe old age of 43. [Source: Jason Bittel, National Geographic, February 8, 2023]

Red bloom tarantulas have stunning red markings on their abdomen. Spiny-backed orb weavers, like the Gasteracantha cancriformis come in a variety of colorations and can be found all over North, Central, and South America. Spiny-backed orb weavers like this Gasteracantha cancriformis may look particularly devilish, but their venom poses no serious threat to humans. Scientists believe the spiny orb weavers (Micrathena sp.) evolved spikes on their abdomens as a way to dissuade predators from taking a bite. The Freya decorata spider is jumping spider is named after the Norse goddess of love and fertility.

As their name suggests, turtle ant-mimicking spiders, like the Aphantochilus rogersi, resemble the ants they prey upon. The last thing that some turtle ants (Cephalotes atratus) see is the face of a turtle ant-mimicking spider. These impersonators can move undetected among the insects and pick them off. There are also ant-mimicking crab spiders in the genus Aphantochilus, native to South America. Their broad, horned faces are strikingly similar to those of the ants they prey on, allowing them to sneak up on their meals without being noticed. As masters of disguise, the predators can be difficult for scientists to find among their prey.

During the rainy season between December and July, males of the species Psecas viridipurpureus put on elaborate dancing displays in an attempt to woo a mate. Some ogre-faced spiders (Deinopis sp.) shows an alternate strategy for catching food with their silken net. Rather than weaving traditional webs, these big-eyed, long-legged arachnids create square nets of silk that they hold with their legs and swat at passing insects. (Ogre-faced spiders have great hearing — without ears.)

Jumping Spiders

Jumping spiders are a group of spiders that make up Salticidae family. As of 2019, this family contained over 600 described genera and over 6,000 described species, making it the largest family of spiders at 13 percent of all spider species. Jumping spiders have some of the best vision among arthropods and use it in courtship, hunting, and navigation. Although they normally move unobtrusively and slowly, they are capable of making impressive jumps, especially when they are hunting, threatened or crossing long gaps.

According to National Geographic Bold jumping spiders (Phidippus audax) have iridescent colorations on their jaws and an inquisitive nature. They don’t spin webs but rather seize prey by ambush. Photographer Javier Aznar said these spiders, which can be found throughout North America, seemed “friendly,” and were not fearful of him. A few jumping spider species also have excellent color vision, so when they turn that puppy-dog gaze your way, they’re actually seeing you. [Source: Jason Bittel, National Geographic, February 8, 2023]

According to Live Science: Body parts that reflect ultraviolet light help male jumping spiders in the Cosmophasis umbratica species catch females' eyes (all eight of them). Males lure the female spiders by striking poses that display these glowing patches prominently. However, female C. umbratica spiders have a glowing trick of their own, possessing palps — a pair of appendages near the head — that fluoresce green in ultraviolet light, which they use to attract the males.

Both male and female spiders rely on these signals to tell who's in a mating mood, scientists discovered in a 2007 study published in the journal Science(opens in new tab). When ultraviolet light was blocked and the spiders didn't glow, they lost interest in mating, the researchers found. [Source: Mindy Weisberger, Live Science, February 14, 2023]

Image Sources: Wikimedia Commons

Text Sources: Mostly National Geographic articles. Also David Attenborough books, Livescience, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Natural History magazine, Discover magazine, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, and various books and other publications.

Last updated December 2024