Unique Characteristics Of Arachnid: 11 Facts You Should Know

Arachnids are invertebrates with unique four paired legs. In this article, you will get to know more about their characteristics and other interesting facts.

  • An arachnid is an arthropod with a unique segmented body.
  • The body of an arachnid is divided into two parts cephalothorax and an abdomen.
  • Arachnids have eight legs, two additional pairs of appendages, and cephalothorax.
  • Arachnids do not have antennae or wings like other arthropods.
  • Some species of arachnids such as scorpion and spiders can be venomous to other animals and some others such as mites inject digestive fluids into the prey.

Are arachnids insects?

Arachnids and insects both come under the same phylum Arthropoda, but due to some characteristics, they are divided into different classes. Let us see if they are same or not.

Arachnids are not insects. The main difference between insects and arachnids is that arachnids can not fly, and they do not have sensory organs like antennae. While insects do not have four paired legs and silk formation organs.

Let us look at some of the major differences given in the table below:

1. Their body is divided into three segments: head, thorax and abdomenTheir body is divided into two segments: cephalothorax and an abdomen
2. They have six legsThey have eight legs.
3. They have antennae or wings.They do not have antennae or wings.
4. Ex. Mosquitos, bugs, bee.Ex. Scorpion, spiders, mites.
The difference between insects and arachnids

Are arachnids bugs?

Bugs are insects and can fly. Let us see if arachnids are bugs or not.

Arachnids are not bugs. Bugs belong to the subclass Hemiptera that have wings and their body is divided into three parts, unlike arachnids, whose body is divided into two parts.

Image Credits: Arachnid by Claudio Gennari
(CC BY 2.0)

Are arachnids cold-blooded?

All arthropods are cold-blooded animals. Let us see if arachnid also falls under this category or not.

Arachnids are cold-blooded, including insects and reptiles. Cold-blooded animals can not maintain their body temperature to match with the weather. In certain conditions, mainly in winter, arachnids enter a state called diapause, where they hibernate themselves without food and supplies.

Are arachnids mammals?

Mammals have a complex body structure and the presence of mammary glands make them peculiar. Let us see if arachnids are mammals or not.

Arachnids are not mammals. They are invertebrates because they do not have a notochord, while mammals are vertebrates and are more evolved and have a notochord. Mammals are comparatively more prominent and robust animals, while arachnids are tiny and fragile.

Are arachnids ectothermic?

Arachnids can not change their body temperature according to the atmosphere. Let us now see if they are ectothermic or not.

Arachnids are ectothermic animals. These animals can maintain their metabolic reactions and activities in different temperatures. Ectothermic species have particular sensory organs that restrict their body heat to transfer conforming to their environment.

Do arachnids have an exoskeleton?

Arachnids do not have complete bone structure like other invertebrates. Let us understand if they lack exoskeleton.

Arachnids have exoskeleton in their structure. The exoskeleton is a defining feature of arthropods that gives protection and support to the body, while endosternite provides internal support.

Are arachnids herbivores?

Arachnid mainly depends on other organisms for food. Let us see if they can be categorized as herbivores.

Only one species of arachnids is classified as herbivorous, and that is Bagheera Kipling. It is commonly known as ‘’the jumping spider,’’ mainly found in Mexico and Costa Rica.

Arachnids are primarily carnivorous such as spiders, scorpions, and mites as they are predators in the ecosystem that feed on other arthropods and their larvae.

Are spider invertebrate or vertebrates?

There are some differences between vertebrates and invertebrates. Let us explore if spider is a vertebrate or not.

Spiders are invertebrates as they do not have a notochord like vertebrates. Invertebrates are small creatures such as insects, spiders and worms, and they cannot grow vertically because they have exoskeletons instead of backbones. They also have an open circulation system and they reproduce fast in numbers.

Image Credits: Arachnid by Claudio Gennari (CC BY 2.0)

Are arachnids parasitic?

Arachnids depends on other bigger arthropods, plants, and animals. Let us see if this feature makes them parasitic or not.

Arachnids can be parasitic. They are found in soil, wood, water and can affect plants and animals, including humans.

Are arachnids reptiles?

Arachnids are non-chordates while reptiles are chordates. Let us see if arachnids can be reptiles or not.

Arachnids are not reptiles; they are arthropods. Reptiles and arachnids are cold blooded, but reptiles are vertebrates and giant animals, while arachnids are invertebrates and minor, comparatively. Reptiles are more evolved than arachnids; they have a more complex structure and different metabolism.


Arachnids play a significant role in balancing the ecosystem. They have appendages for locomotion, feeding and reproduction. Some arachnids, like solifugae, have more than eight legs, while some only use six for locomotion and the first two for feeding and protection, called the chelicerae.

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