Spiders
Class Arachnida
Spiders Facts and Information
Spiders are not classified as insects but as arachnids, which have eight legs and a body divided into two sections, unlike insects which have six legs and a body split into three sections. There are more than 45,000 spider species found in ecosystems worldwide, ranging in size from the tiny Samoan moss spider measuring just 0.011 inches to the large Goliath birdeater tarantula with a leg span of up to a foot. Although the majority of the nearly 4,000 spider species found in the United States are not harmful to humans, some spider bites can result in painful sores that can take up to a month to heal. A few species of spiders are venomous to humans, such as the black widow and the brown recluse, which can cause serious health issues, including damage to tissues or the nervous system.
Spiders and insects can be distinguished by their physical characteristics. Unlike insects, which have three body segments, spiders have two: the cephalothorax and the abdomen. The cephalothorax houses the eyes, mandibles, legs, and abdomen. Insects have three pairs of legs, while spiders have four. Additionally, spiders have modified appendages called pedipalps that are located in front of the mouth, resembling an extra pair of legs in some species. Most spiders have eight eyes on the front of their cephalothorax, although some have fewer, and the positioning of these eyes is used to distinguish different species. The unsegmented abdomen contains the genital parts, spiracles, and spinnerets for spinning silk. Although the abdomen of most spiders is not segmented externally, it is connected to the cephalothorax by a narrow waist called the pedicel. Spider sizes range from 0.5 to 90 mm, depending on the species.
FAQs About Spiders
What are the various types of spiders?
There are many different types of spiders found around the world. Here are some of the main groups:
- Orb Weavers: These spiders build large, circular webs that are often used to catch flying insects.
- Jumping Spiders: These spiders are small and can jump up to six times their body length to catch prey.
- Wolf Spiders: These spiders are fast runners and actively hunt down their prey.
- Tarantulas: These are large, hairy spiders that are often kept as pets. They are found in tropical and desert regions around the world.
- Crab Spiders: These spiders are known for their ability to change color to match their surroundings, allowing them to ambush prey.
- Fishing Spiders: These spiders can walk on water and even dive to catch aquatic insects and small fish.
- Nursery Web Spiders: These spiders build a web to protect their eggs and young until they are ready to hatch.
- Ground Spiders: These spiders are found in a variety of habitats and actively hunt their prey on the ground.
- Funnel Web Spiders: These spiders build a funnel-shaped web that traps prey.
These are just a few examples of the many different types of spiders. Each type has its own unique characteristics and behaviors.
What do spiders eat?
Spiders are carnivorous and typically feed on other insects and arthropods, such as flies, mosquitoes, grasshoppers, and moths. Some larger species of spiders are known to prey on small vertebrates like lizards, birds, and even small mammals like mice. Spiders use their venom to subdue their prey, which they then consume either by biting them or by wrapping them in silk to immobilize them. Some spiders also engage in cannibalism, with larger individuals feeding on smaller ones of their own species.
What are the sign and symptoms of a spider bite?
The signs and symptoms of a spider bite can vary depending on the species of spider, the amount of venom injected, and the individual’s reaction to the venom. Here are some common signs and symptoms of spider bites:
- Pain and swelling at the site of the bite
- Redness and itching
- Muscle pain and cramping
- Chills and fever
- Headache
- Nausea and vomiting
- Sweating
- Skin lesions or blisters
- Difficulty breathing or swallowing (in severe cases)
It’s important to note that not all spider bites result in symptoms, and most spiders are not harmful to humans. The two most dangerous spiders in the United States are the black widow and the brown recluse, and their bites can cause severe symptoms. If you suspect you have been bitten by a spider and are experiencing symptoms, it’s important to seek medical attention right away.