It’s a common misconception to think of spiders as insects, but the reality is quite different. Spiders belong to a separate class of arthropods and have distinct characteristics that set them apart from insects.
In this article, we’ll find out why spiders are not considered insects, the differences between the two groups, and the significance of understanding these differences.
Legs
Spiders can easily be identified by their eight legs, which are all attached to the cephalothorax. This feature makes them highly efficient hunters. Insects, on the other hand, have six legs connected to the thorax, with many species also possessing wings for mobility.
Antennae
Unlike insects, which use a pair of antennae for sensing their environment, spiders lack antennae entirely. Instead, they rely on specialized sensory hairs on their legs and body to detect vibrations and chemical signals.
Visit our Species, Control, and DIY Guide sections for additional resources on spiders and ways to tackle a spider infestation.
Are Spider Insects?
Spiders and insects are both part of the phylum Arthropoda, which also includes crustaceans and millipedes. However, they belong to different classes, with spiders classified as arachnids and insects falling under the class Insecta. Arachnids, such as spiders, scorpions, ticks, and mites, have eight legs, lack antennae, and have bodies divided into cephalothorax and abdomen. In contrast, insects, including ants, butterflies, beetles, and flies, have six legs, a pair of antennae, and bodies divided into three segments: head, thorax, and abdomen. Many insects also possess wings. While spiders and insects share certain characteristics as arthropods, their distinct anatomical and structural features set them apart.Why Is a Spider Not an Insect?
Although spiders and insects are both members of the arthropod family, their distinct anatomical and biological differences place them in separate classifications. Spiders are from class Arachnida, while insects are part of the class Insecta. Body Structure Spiders have two main body segments. First is the cephalothorax (a fusion of the head and thorax) and second is the abdomen. This compact structure aids in their predatory lifestyle. While on the other hand, insects have three body parts, the head, thorax, and abdomen. This division allows for specialized functions like flying or carrying sensory organs.
Legs
Spiders can easily be identified by their eight legs, which are all attached to the cephalothorax. This feature makes them highly efficient hunters. Insects, on the other hand, have six legs connected to the thorax, with many species also possessing wings for mobility.
Antennae
Unlike insects, which use a pair of antennae for sensing their environment, spiders lack antennae entirely. Instead, they rely on specialized sensory hairs on their legs and body to detect vibrations and chemical signals.
Visit our Species, Control, and DIY Guide sections for additional resources on spiders and ways to tackle a spider infestation.
Key Differences Between Spiders and Insects
| Feature | Spiders (Arachnids) | Insects (Insecta) |
|---|---|---|
| Number of Legs | 8 | 6 |
| Body Segments | 2 (cephalothorax + abdomen) | 3 (head, thorax, abdomen) |
| Antennae | None | 1 pair |
| Eyes | Typically 8 eyes | Usually 2 compound eyes |
| Wings | None | Many have wings |
| Development | Direct development (no metamorphosis) | Complete or incomplete metamorphosis |
