Spiders belong to the group of animals called arthropods, which in addition to spiders, also contains animals like lobsters, crabs, mites, insects, centipedes, and millipedes.
The main distinguishing feature that unites all arthropods is their external shield made of chitin. The purpose of the chitin exoskeleton is to protect the arthropod from attacks by other animals and protect its internal organs.
Spiders also share other features with other arthropods, such as segmented bodies and molting. There are also four subgroups (subphyla) within the arthropod family of animals: arachnids (where spiders belong), crustaceans, insects, and millipedes and centipedes.
What Makes a Spider an Arthropod?
Spider is an arthropod because of its chitin shield that acts as an external skeleton, it has a segmented body (head, thorax, abdomen), it has appendages on its body (legs and hairs), and it has a nervous system.
The phyla of arthropods is a very broad family of animals, and it’s the largest group of animals out there. It’s even estimated that 80% of all animals belong to the group of arthropods!
In this same group, you’ll find animals like insects, spiders, crabs, centipedes, and even pill bugs.
All of these animals share some common features, even though the group of arthropods is quite large. They all have an external skeleton made of chitin. This chitin protects the animal against attacks from other animals. They have segmented bodies and the vast majority of arthropods have appendages on their bodies.
These are the main features that all arthropods share, but there are also nuances within the arthropod group of animals.
There are four subphyla within the arthropod group of animals:
- arachnids (spiders)
- mites and ticks
- arachnids (spiders)
Spiders belong to the arachnid group of animals. All arachnids have four pairs of legs (eight legs in total), they also have pedipalps and chelicerae, which serve them for feeding and catching prey. They don’t have antennas on their bodies but they do have an internal breathing system, which allows them to survive on land.
Other features that mean spiders belong to the group of arachnids within the larger group of arthropods include their carnivorous nature and the fact that most spiders have venom, which is also true for most other arachnids.
Why Are Spiders Arachnids?
Spiders are arachnids because they have four pairs of legs and two additional appendages (chelicerae and pedipalps), and their body is organized as a cephalothorax (head, thorax, and abdomen).
The vast majority of arachnids live on the land, but there are also some animals within this group of animals that are able to survive underwater. Daddy-long-legs and spiders are often thought of as the same species, but daddy-long-legs have some distinct features that make them separate species.
All arachnids belong to the larger group of animals called arthropods. However, even arachnids are not all the same.
Within the arachnid subphyla of animals, you’ll also find four separate groups: spiders, daddy-long-legs, scorpions, and ticks and mites.
Because arachnids still fall under the family of arthropods, they will still have all of the main distinguishing features that make them arthropods. They still have chitinous shells and have a cephalothorax, but they are vastly different from other arthropods, like for instance, some insects that have wings.
How Are Spiders Different From Other Arthropods?
Spiders have eight legs, don’t have wings, and don’t have antennas, which makes them the only group of animals to not have them within the arthropod family.
Arthropods, or Arthropoda, are a very broad group of animals. They all share some similar characteristics such as chitinous shells and a lack of spine or bones, but they are also vastly different from one another.
Spiders are unique in their own way. They belong to the group of arachnids because of their eight legs and no wings. Other features that make spiders different from other animals include:
- A lack of antennas – this is perhaps the most distinguishing feature of spiders. Some other arthropods have antennas – in fact, the majority of animals within this group do have antennas, but spiders use other senses to detect the world around them.
- Spiders have eight legs – they have eight legs as compared to other animals that only might have six; on the other hand, some other members of the same group of animals will have more than a dozen of legs, while a centipede might have up to 30 legs.
- They don’t have wings – some other arthropods like insects, for example, have wings, while spiders don’t.
- Spiders have hair on their bodies – hair on the pedipalps and on the body of the spider allows the spider to detect the animals around them and sense the vibrations, which makes them unique in their own way. Instead of antennas, spiders use their hairs to sense vibrations and the world around them.
- Spiders create webs – this is yet another distinguishing feature of spiders and one that almost no other animal has. With their webs, they are able to capture their prey and protect their eggs.
Again, the group of arthropods is a very diverse group and it consists of the most species in the world. You’ll find anything from flying insects, to scorpions, and even to spiders, so it’s hard to really compare two animals from this group and see them as the same species.
Spiders are arthropods, but they do belong to a subgroup of arthropods called arachnids. They share the main features of arthropods, such as segmented bodies and a chitinous shell.
However, they’re also vastly different from most other arthropods. That’s partly because this group of animals is so diverse, and partly because of the unique structure of spiders. They don’t have wings like some insects, but they have hairs on their bodies and they can create webs, which is something that almost no other animal in this world can do.