What are spiders?

Updated on: January 24th, 2025

What are spiders, and how do they differ from insects? Spiders are arachnids. They have eight legs rather than six and a body split into two sections instead of three. Spiders play several critical roles in ecosystems, primarily through pest control, as they prey on insects and other small arthropods. While many fear spiders, they are generally harmless to humans and help control pest populations in homes and gardens.

Typical spider anatomy

Spiders have a distinctive anatomy characterized by two main body segments: the cephalothorax and the abdomen. They have eight legs, all attached to the cephalothorax, and typically have eight eyes arranged in two or three rows.

What are spiders' main body parts, and how do they use them for hunting? Spiders have fangs connected to venom glands for injecting venom into prey, and they use their legs to detect prey vibrations. At the rear of the abdomen are silk glands connected to spinnerets, which produce silk for webs. Webs allow them to catch prey more easily.

If spiders are infesting your home, it's best to contact a professional for spider control. They can identify the size of the infestation and determine the spider species present.

Spider life cycle and reproduction

The spider life cycle consists of three phases: egg, spiderling, and adult. The duration of each phase varies depending on the species and environmental conditions.

1. Egg: Eggs hatch into spiderlings, which undergo multiple molts to become juveniles.

2. Spiderling: Spiderlings undergo multiple molts as they grow. This process can take several weeks to months.

3. Adult: Adult spiders are capable of reproduction. Spider reproduction typically involves courtship rituals, where males use various behaviors, vibrations, and pheromones to attract females.

Common types of spiders

It's estimated that there are over 45,000 spider species worldwide, with many more awaiting discovery and classification. Some common types of spiders include:

• House spider: Often found indoors, house spiders are known for building messy webs in corners and crevices.

• Cellar spider: Often referred to as daddy-long-legs spiders, cellar spiders have long, delicate legs and are commonly found in dark, damp areas like basements and cellars.

• Black widow spider: Black widow spiders are venomous and found in various regions worldwide. They can be recognized by their shiny black bodies and red hourglass markings, although not all black widows have them.

• Wolf spider: Typically ground-dwelling hunters, wolf spiders are robust and fast-moving.

• Brown recluse spider: This venomous spider is known for its distinctive violin-shaped marking on the cephalothorax and its preference for hiding in dark, secluded places.

Other types of spiders include:

• Crab spider
• Garden spider
• Hobo spider
• Joro spider
• Jumping spider
• Spiny-backed orb weaver spider
• Tarantula spider
• Yellow sac spider

Which spiders are dangerous?

The funnel-web spider and its relatives are among the deadliest spiders in the world. They produce a highly toxic venom that can be lethal to humans, especially if untreated. The venom can cause a rapid onset of symptoms, including severe pain, sweating, muscle spasms, and respiratory distress.

Several other spider species are considered dangerous due to their venomous bites and potential harm to humans, including the:

• Black widow spider: Black widow spiders are found worldwide and are known for their potent neurotoxic venom.

• Redback spider: Native to Australia, the redback spider is closely related to the black widow, and its bites can cause intense pain.

• Mouse spider: Found in Australia, mouse spiders are related to funnel-web spiders and produce venom that can cause severe illness in humans, including nausea, vomiting, and chest pain.

• Recluse spiders: Various species of recluse spiders have venom that can cause necrotic skin lesions.

These spiders should be treated with caution, and medical attention should be sought promptly if bitten.

Spider bites

While all spiders are physically capable of biting, most only bite humans if they're provoked or feel threatened. When a spider does bite, the effects can vary depending on the species and individual circumstances.

The different spider habitats

Nearly all spiders fall into one of two categories: hunting spiders and web-building spiders. Hunting spiders actively hunt and capture prey rather than relying on webs to trap food. Web builders are more likely to go indoors and construct intricate webs to capture prey.

Spiders are incredibly adaptable and are found on every continent except Antarctica. They can thrive in diverse habitats worldwide, inhabiting environments from tropical rainforests to arid deserts. Some common places where spiders can live include:

• Indoors: Many spider species are adapted to living in houses, sheds, and garages. They seek out dark, secluded areas like closets, attics, and basements where they can build webs and hunt for prey.

• Outdoors: Spiders can be found in almost any outdoor environment. They can inhabit vegetation, tree bark, leaf litter, and rocky crevices. They'll also build webs between plants or rocks to capture prey.

• Moist environments: Some spider species prefer damp or humid conditions and can be found near streams, ponds, marshes, soil, rotting wood, and mossy areas.

• Dry environments: Other spider species are adapted to arid or desert environments and can be found in sandy or rocky habitats.

Spider webs

Spider webs serve multiple purposes for spiders, including catching prey, providing shelter, and helping with reproduction. Webs are made primarily of silk, produced by specialized glands in the spider's abdomen. They manipulate the silk threads using their legs, weaving them into intricate patterns tailored to their hunting strategies and environment. Once the web is complete, spiders wait for prey to get caught in the sticky silk threads.

There are several different types of spider webs.

1. Orb webs are circular or oval-shaped webs constructed by orb-weaving spiders. They have radial support lines with spiraling sticky threads that capture flying insects.

2. Cobwebs are irregular, messy webs that are constructed with a combination of sticky and non-sticky silk. They are often used for shelter rather than prey capture.

3. Funnel webs are sheet-like webs with a funnel-shaped retreat at one end. They are used to capture prey and provide shelter.

4. Sheet webs are horizontal, flat webs with a dense mat of silk and a few supporting threads. They are often found on vegetation or near the ground.

5. Trapdoor webs consist of a hinged lid covering a silk-lined burrow. The spider waits inside the burrow for prey to wander by before ambushing it.

What will help keep spiders away?

To help prevent spiders from entering your home, keep outdoor areas clear of wood piles and stones where they could dwell. Seal cracks and use screens on doors and windows. Clean and vacuum regularly, and reduce outdoor lighting to help deter insects that spiders prey on.

If spiders are infesting your home, consider one of our ongoing pest protection plans. Our PestFree365 plans include a multipoint interior and exterior inspection and regularly scheduled pest treatments. Our PestFree365 plan includes protection from 25 common household pests, and our PestFree365+ plan provides protection from 39 household pests, including black widow and brown recluse spiders.