Spiders are fascinating creatures that have long captivated human interest. They are found in nearly every region in the world, from lush rainforests to the merciless desert. There are even spiders in Antarctica!
While many people fear spiders, these arachnids serve a critical role in the delicate balance of nature.
Let’s look at the many sides of the spider world, from physical traits and behavior to ecological influence and cultural significance.
Spider Evolution
Studies show that spiders existed 380 million years ago in the Devonian period. The oldest spider fossils found date back to the Carboniferous period, 300 million years ago.
To survive, they evolved to become better predators. Their adaptations included making silk, having venomous fangs, and developing other organs to sense their surroundings.
Classification
Spiders, like other living animals, are classed according to their traits and evolutionary ties.
They belong to the Arachnida class, which also includes ticks, scorpions, and mites. They’re part of the order Araneae, which is split into around 100 families.
Different types of spiders are identified based on the number and placement of their eyes, fangs, and silk-producing organs.
Types of Spiders
The 48,000 plus known spider species are divided into three main types. These are true spiders, false spiders, and harvestmen.
True spiders, including cobweb maker, wolf spider, and orb weaver, build webs to catch their prey. False spiders, like daddy-long-legs, don’t spin webs but hunt instead. Harvestmen look like spiders but aren’t – they have two body parts and super long and thin legs.
Suborders
The order Araneae is split into two suborders – Mesothelae and Opisthothelae. Mesothelae only has a few species of primitive spiders found in Southeast Asia, while Opisthothelae is home to all other living spider species.
It’s further divided into two groups: Mygalomorphae (aka ‘true spiders’) and Araneomorphae (‘modern spiders’). Mygalomorphae are the oldest and can get quite big (think Tarantulas, Trapdoor spiders, and Funnel-web spiders). Araneomorphae is more diverse and comes in all shapes and sizes.
Within Araneomorphae, there are several superfamilies, including: 
- Araneoidea: Orb-web spiders
- Thomisoidea: Crab spider
- Salticoidea: Jumping spider
- Lycosoidea: Wolf spiders
- Oxyopoidea: Lynx spiders
- Anyphaenoidea: Anyphaenid sac spiders
These large groups are further divided into smaller families, genera, and species. The second subdivision is based on different genetic and physical traits.
Species of Spiders
It’s estimated that there are around 49,000 known spider species, but that’s just the tip of the iceberg.
There are likely more that haven’t been discovered or classified yet. Every year, experts find and identify new spider species so that this total number could be anywhere from 100,000 to 170,000.
Fun Facts
Here are some fun facts about these amazing species.
- Some spiders can glide or balloon through the air, but no wings are involved. It’s called ballooning – they release a stream from the silk gland that catches the wind and carries the spider with it, allowing them to travel long distances and colonize new habitats, usually found in tropical areas.
- Certain species are incredible jumpers who can leap up to 50 times their body length!
- They have incredible vision; some have front eyes divided into two parts – one for detecting movement and the other for long-range vision.
- No teeth for these arachnids, though, as they use their fangs to inject venom into their prey.
- Spiders help the environment by controlling bug populations, estimated to eat 800 million tons of insect prey annually.
What Do Spiders Look Like?
Spiders have widely varied physical traits. Their colors alone range from light brown to black to brightly hued. These arachnids have two primary body parts, the cephalothorax and the abdomen. All spiders have eight legs, and most have four pairs of eyes.
Size
Spiders come in quite an array of sizes. They vary from minute dwarf spiders (1-2mm) to massive tarantulas that reach up to 12 inches wide.
Generally, female spiders tend to be bigger than males, a phenomenon known as sexual dimorphism. A few species also have males with unique features like horns and big chelicerae that they use in attempts to win a mate.
Colors
Spiders come in all kinds of colors and patterns that make them stand out from each other. Some hide by blending in with the background, while others use bright and bold colors to show predators they’re poisonous.
Some can even change their color based on the light and angle, like Iridescent spiders that display red, blue, and green. And then there are the Aposematic ones in the tropics with red and orange hues to warn potential predators.
Plus, some spiders change their color depending on the season, helping them blend in and stay safe from predators. You can find these camouflaging critters in tropical environments where they adapt to their surroundings.
Eye Spy
Few spiders have up to 12 eyes, and some have none at all. Most have 8, while some may have 6, 4, or 2. Even with multiple eyes, they don’t always use them for sight; some use them to sense light and dark.
Eye numbers and placement vary, with few species, like Jumping spiders having quite big eyes that make them look almost human-like.
Pygmy spiders tend to have 3 rows of 4 eyes, and Ogre-faced spiders have 2 large eyes and 6 smaller ones in the middle of their heads – this gives them a wide view to spot prey.
Most spiders also have night vision and can detect UV light. This is quite helpful when they’re hunting at night since many of them are nocturnal.
Distribution & Habitat
Spiders are everywhere – deserts, jungles, and even Antarctica! They usually stay on land, but some species love the water.
In their natural homes, spiders like dark and quiet spots like crevices, under stones, logs, in soil, and burrows. They are usually found near their food sources, like insects, other animals, and nectar-producing plants.
Physiology
Spiders are fascinating creatures with two main body segments, eight jointed legs, and multiple eyes. Plus, they have a unique respiratory and circulatory system that helps them survive even in the toughest environments.
Studying their physiology gives us better insight into their amazing adaptation and evolution.
Body Plans
Spiders’ body plans can be totally different from one another. Most spiders have two parts: their cephalothorax (with the eyes and mouthparts) and the abdomen (with the heart and digestive system).
Some spider species have extra body parts, like additional appendages on some tarantulas.
Circulatory System
Spiders have an open circulatory system with a heart, aorta, and connected vessels. That means their hemolymph (which is like blood) isn’t kept in vessels like mammals; it just flows freely around the body cavity.
The heart pumps hemolymph into the aorta and sends it to the organs like the legs, abdomen, and cephalothorax. Then it goes through the book lungs, which take oxygen from the air and return it to the heart.
Unlike a closed circulatory system, no capillaries are involved, and all the blood vessels are connected. This is related to the spider’s respiratory system, which, unlike ours, doesn’t involve air passing through the lungs.
Excretion & Digestion
Spiders have a unique (to put it politely) digestive system. Their mouthparts are adapted for their venom and to bite prey, and their potent chelicerae have fangs that inject powerful venom for digestion.
Basically, their digestive process consists of two parts: the foregut breaks down food into small pieces, and the mid-gut absorbs the nutrients.
Enzymes and sucking muscles liquefy the food before it’s digested. Fascinatingly, spiders control their excretion process, adjusting the amount and composition of the white solid substance (guanine) they release through the spinnerets at the bottom of the cephalothorax for optimum nutrient absorption.
Nervous System
Spiders have a sophisticated neural system. The brain is located at the front of the head to process sensory input and control behavior. A ventral nerve cord runs the length of the body, with nerve fibers sending signals to and from the brain.
These unique creatures have an array of senses to help detect prey, predators, and environmental changes, including tactile, visual, and chemical receptors.
Their eyes contain various photoreceptors to see in low light and even detect UV light – something other animals can’t. Spiders even have sensory hairs and spines on their body that alert them to prey or predator movement.
Sensory Organs
Spiders possess a variety of sensory organs that help them stay aware of their surroundings. They have sensillae for feeling vibrations, trichobothria for detecting air pressure shifts, coeloconic sensilla for smells and tastes, and Malpighian corpuscles for sensing temperature changes.
All of these work together to help spiders detect their environment and act accordingly. The organs also assist in locating prey, finding food and water, and avoiding potential dangers.
Locomotion
Spiders’ locomotion is a true testament to their survival. Some scuttle with four pairs of legs, while others have gotten more agile and can jump. Some even use thin strands of silk to climb vertical surfaces that would be impossible to reach any other way.
A few species have even taken to the skies and can fly long distances like flying insects.
Respiration
Respiration is essential for all living creatures, even spiders! All spiders need oxygen to stay alive, so they need a way to take in oxygen and let out carbon dioxide constantly. This is done through important organs called book lungs.
Reproduction & Life Span
Spiders have unique reproductive strategies – they need both male and female spiders to get the job done! Males generally display complex courtship behaviors to attract females, while females take a more passive approach.
After mating, the female produces an egg sac in a silk cocoon that the male fertilizes. The cocoon is hidden away for several weeks so the eggs can go through molting, allowing baby spiders to develop.
Once hatched, the spiderlings feed on small insects for energy and nutrients as they molt and grow until the young spiders finally reach their adult form and size.
Depending on the species, they can lay anywhere from a few eggs up to 600 in their lifetime – quite impressive for creatures who only live a few months to two years!
Silk & Venom (Not a Romance Novel Title)
Spiders are known for their specialized features, like poisons used for hunting and defense. A vast majority of spiders have venom glands that produce toxins to immobilize or kill their prey. Spider venom is complex, with numerous possible compounds. This is why making antivenoms can be a difficult task.
Another thing spiders are known for is their silk. This substance is utilized for hunting, building webs, protecting eggs, and even flying!
Spider silk is a truly remarkable material. It is renowned for being stronger than steel, more elastic than rubber, and more absorbent than cotton. This silk is used for applications such as medical sutures, tissue engineering, and even bulletproof vests.
Dining Options
Spiders use their strong, intricate mouths to catch and eat their meals. Instead of going out and actively hunting for food, some prefer to just stay in their web and wait for their next prey.
They use their eyesight, touch, and smell to find their meals and then spin webs or use venom to paralyze them. Some even have special strategies to catch their food, like ambush hunting.
Silent Stalkers
Spiders often exhibit stalking behavior, staying motionless until the prey is within reach, then approaching with stealth until they are close enough to attack. This is an effective method for spiders to catch food and defend themselves from predators.
Behavior
Spiders are intricate in nature, and this is reflected in their behavior. They show advanced predatory and defensive moves; some even have complicated courtship rituals. All true spiders spin webs, which they use either to trap food or for mating.
Non-Predatory Feeding
Spiders who don’t hunt their food usually build webs to trap their prey. Some spiders eat dead insects, dung, and other matter. Others even take advantage of other spiders or insects.
Spiders spin webs to snare their prey – the size and shape of the web depend on the species. When an insect or another creature gets stuck in the tacky silk, the spider can then quickly kill it.
Parasitic spiders live on or inside their hosts and feed off their bodily fluids. They even lay eggs on or inside their host’s body, eventually killing it.
Talented Hunters
Spiders are formidable hunters. They have a wide variety of strategies to catch their prey, such as their webs, burrowing, jumping, and trapping. They are also very cunning and adept at surprising their victims. These skills make spiders some of the most efficient predators in the animal world.
Defense
Spiders have a formidable defense tactic: they produce silk. This material is used to build webs to capture prey, construct shelters, and defend against foes. They also have highly sensitive hairs on their legs that pick up vibrations. This can be indicative of a threat.
Socialization
Spiders have some social traits, like searching for food and investigating their environment as a group. Yet they are mainly solitary creatures.
When they do interact, it usually happens between different species, and it can be either friendly or hostile depending on the type of spider. They can also construct webs together, making hunting and sharing food easier.
Web Types
Depending on the species, spiders can build different types of webs. Funnel, sheet, tent, and cobwebs are some of the more common ones. The web type a spider uses depends on its surroundings and the type of prey it seeks.
Orbs
Orb webs are usually round, made from silk, and evenly spaced. Orb spiders build these webs near open fields or gardens as a way to catch their prey. Plus, these webs are strong, so they can be used for studying the mechanics and physics of engineering.
Cobwebs
Cobwebs are a telltale sign of spiders. They weave these intricate, sticky silk webs to trap their food. Although they may be a nuisance to humans, cobwebs are essential for spiders as they provide them with sustenance and shelter.
Zero Gravity Webs
There are studies underway on how spider webs perform in zero-gravity conditions. The results provide data on how gravity impacts the construction process. Experts are also obtaining new insight into the properties of spider silk. In order to create a 0-G web, a specific mindset is necessary.
Strength and material need to be taken into consideration to make sure the web stays put in a weightless atmosphere. This application could be helpful in fields like materials science and engineering.
Global Population
There’s no exact number for the world’s spider population. This is due to variations in location, the type of species, and habitat.
A few studies have tried to estimate the spider population in different areas. For example, one showed there could be between 50 and 200 spiders per square meter in the tropics, while another claimed there could be up to 500 per square meter in grasslands.
Can Spiders Cause Harm?
While some species, like the Black Widow spiders and Brown Recluse, can bite humans and cause severe reactions, most species are not dangerous. In fact, many are beneficial to us and the environment.
They help keep the natural balance of ecosystems by helping to control pests like insects, mites, and other small creatures. Plus, they regulate the population of other predators and parasites. On top of that, some spiders even act as pollinators, so they’re star contributors to the pollination process.
Interaction With Humans
Many spiders are harmless, even helpful. Yet some varieties can be dangerous if they bite. To stay safe when interacting with spiders, it’s important to take necessary precautions. Just remember, spiders play a key role in controlling insect populations and keeping our environment balanced.
Media Misconceptions
The media and public have had a bad opinion of spiders for ages. Sure, some spiders can be dangerous, but the reality is that most of them aren’t, and they fulfill an important role in our ecosystem.
Bite Symptoms
A spider bite can range from harmless to life-threatening. Most spider bites are not dangerous and may result in minor pain, redness, and swelling. However, certain types of spiders possess venom that can cause severe reactions and require immediate medical attention.
Black widow bites can result in severe muscle cramps and abdominal pain. Brown recluse bites leave visible tissue damage and a trademark “bull’s eye” lesion. There have been cases where spider bites have proven fatal.
If you suspect that a spider has bitten you, and experience severe pain, muscle cramps, fever, chills, vomiting, or difficulty breathing, seek professional treatment as quickly as possible.
Silk Stats
Spider silk is one of nature’s most unique materials. It is malleable enough for spiders to use to catch prey and build complex webs. At the same time, it is only 0.0001 inches thick and five times stronger than steel of the same size. Plus, it’s incredibly lightweight, making it an ideal material for many industrial uses.
Arachnophobia: A Common Condition
Arachnophobia, or the fear of spiders, has existed for millennia. This common condition still affects people all over the world today. People with arachnophobia (including yours truly) experience intense anxiety or fear at the mere sight of a spider, even if it is only an image.
Some are so afraid they actively avoid situations or places where spiders are likely to be present. There is help for those with this phobia. Several treatments have been developed over the years to help people manage their fear, including:
- Cognitive-behavioral therapy (CBT) – A form of psychotherapy that helps people identify and modify the thoughts and behaviors that contribute to their phobias.
- Medications – Prescribed medications such as antidepressants and anti-anxiety medications can help reduce feelings of fear and anxiety.
- Exposure therapy – A type of therapy in which people are exposed to the object of their fear in a controlled, safe setting, allowing them to learn to manage their fear and reduce the intensity of their reactions.
An Unusual Delicacy
In some parts of the world, spiders are a delicacy. Many eastern nations enjoy meals that feature cooked spiders as a star ingredient. Those who have tried such cuisine describe the flavor as a unique blend of chicken and cod. Apparently, the texture of a spider is comparable to that of shrimp. I’ll take your word for it.
Mythology and Meaning
Spiders have been a significant part of human history, from ancient civilizations to modern cultures. They have played such an integral role in humanity that numerous societies have included spiders in art, folklore, and literature.
One example is the classical Greek myth of Arachne. This mortal woman was so proud of her weaving skills that she boasted they surpassed those of the goddess Athena. This did not bode well with the goddess, so she turned Arachne into a spider. The word “arachnid” comes from the unfortunate woman’s name.
Some Native American tribes revere spiders as symbols of creativity and protection, while African folklore depicts spiders as tricksters.
On the other hand, the Titular spinner in the beloved Charlotte’s Web was a wise and compassionate soul. In stark contrast was Shelob, a massive spider created by Tolkien that is nothing less than a horrifying nightmare.
Threats to Spiders: The Struggle for Survival
Spiders face several threats to their population, from habitat destruction to the use of pesticides and even climate change.
Habitat loss is likely the most pressing issue for spiders. Forests and wetlands are some of their favorite places to call home. Yet, as humans continue encroaching on these natural lands, spiders are forced to compete for resources and space with other species. This puts their numbers in decline.
The use of pesticides is another cause of spider deaths. As humans use these chemicals to manage pests, they can inadvertently poison spiders too. If that wasn’t bad enough, these pesticides reduce the food supply of spiders, further weakening their populations.
Climate change has become a major concern for spiders. Rising temperatures and changes in precipitation create increasingly inhospitable conditions for them. Even more concerning, the introduction of unfamiliar weather patterns can reduce the number of spiders in an area.
Summing Up Spiders
Spiders are remarkable creatures. They’ve been on this earth for millions of years and assist humans by reducing the number of disease-carrying insects. They also provide a food source to other animals, such as birds.
Whenever we step outside, we’re surrounded by these gifted arachnids that hunt and display unique behaviors while keeping ecosystems in balance.
Spiders are complex creatures capable of incredible feats like hunting, socializing, and defending themselves. Despite chilling stories and their foul reputation, we should appreciate spiders and strive to coexist with these fascinating beings.
