According to the Smithsonian Institute, there are upward of 10 quintillion insects on the earth at any one time, but spiders are not part of that number because spiders are not insects. So, how are spiders related to insects? Which characteristics do they have in common, and which are different?
Spiders and insects are part of the scientific phylum known as Arthropoda. The word arthropod translates to “jointed foot.” Arthropods make up the largest group of invertebrate animals. Since spiders and insects are part of this same large group, they have many things in common, such as:
- A body divided into distinct sections
- An even number of jointed limbs (paired appendages)
- No backbone (invertebrates)
- Growth through the molting process
At some point, hundreds of millions of years ago, arthropods began to evolve separately, and different classes emerged. A class refers to a group of related animals. In this case, insects are grouped into the class Insecta and spiders belong to the class Arachnida.
The shared history of spiders and insects accounts for the similarities mentioned above. The branching off into separate, distinct classes means that there are many differences. Let’s take a closer look at what makes spiders different than insects like flies, roaches, beetles, fleas, ants, and more.
Number of Body Parts
Insects have 3 main body parts, the head, thorax, and abdomen. An insect’s 3 pairs of legs are attached to its thorax. Spiders have only 2 main body parts. The head and thorax of arachnids are combined into what is classified as a cephalothorax. They also have an abdomen.
Number of Legs
All insects have six legs. Spiders and other arachnids (mites, ticks, scorpions) have 8 legs. Arachnids also have extra appendages that may be mistaken for legs including: chelicerae (mouthparts that may be fangs or pincers) and pedipalps (used to help break up food and aid in reproduction).
Number and Type of Eyes
Most insects have 2 large eyes, though some can have up to five. These eyes are usually compound eyes with many lenses. Spiders typically have 8 eyes, though some species have 6 or fewer. Spider eyes consist of a single lens, and most spiders have poor eyesight.
Antenna and Wings
Insects have jointed appendages on their heads, known as antennae, that help them do things like feel, taste, and smell. Many species of insects also have wings and fly. Spiders do not have antennae or wings.
As you can see, spiders and insects are actually quite different. Knowing their unique characteristics and behavior can help you better identify and control spiders. PF Harris has the information and products you need to take care of spiders around your house. Our spider traps help to monitor the spider situation and can alert you to a potential problem. Harris Spider Killer is an excellent contact killer that can be used indoors or outdoors. For more information, check out Spiders: The Ultimate Guide.