Difference Between Insects and Arachnids


Main Difference

The main difference between Insect and Arachnids is that Insect is an invertebrate with three body segments, compound eyes, and a pair of antennae, whereas Arachnids are invertebrates which possess two body parts, simple eyes, and no antennae.

Insects vs. Arachnids

The insect is a Latin word, and arachnid is a Greek word. Insects belong to class Insecta; on the other hand, arachnids are a member of class Arachnida. The eyes of insects are compound, whereas arachnids have simple eyes. The insect has an antenna in its head region; on the flip side, the antennae are absent in arachnids. Insects have three pairs of appendages; on the contrary, arachnids have four pairs of appendages.


The body parts of insects are the head, thorax, and abdomen, while cephalothorax and abdomen are two body segments of arachnids. Most of the insects have evolved wings; on the other hand, arachnids lack wings. Insects move by swimming, walking, or flying; on the flip side, arachnids move by creeping or crawling.

Insects pass through a complete process of development by metamorphism, whereas arachnids undergo uncomplete metamorphism. Insects have about 10 million species; on the other side, the species of arachnids are about one lac. Insects can exist in all habitats, whereas most of the arachnids live on land. Insects use trachea as an organ for respiration; on the converse side, the organs for respiration in arachnids are trachea and book lungs. The blood of insects is colorless, while arachnids have blue-colored blood. Some of the examples of insects are beetles, ladybirds, ants, bees, butterflies, and mosquitoes. Spider, ticks, mites, scorpions; on the flip side, harvestmen are some examples of arachnids.


Comparison Chart

Insects are small animals categorized as invisible to 7 inches long.Arachnids are small, creepy, and crawling animals.
Compound eyesOne to six pairs of Simple eyes
A pair of antennaeNo
Body Segments
Most insects have wingsNo wings
Complete metamorphismUncomplete metamorphism
six to ten millionOne lac named species
Exist in all environmentMainly terrestrial
TracheaTrachea and book lungs
Colorless bloodBlue colored blood
Beetle, flies, butterflies, fleaSpider, ticks’ scorpions, harvestmen

What are Insects?

An insect is small microorganisms categorized as hexapod invertebrates. The class Insecta is the most significant class in phylum arthropod. Some of the characteristics that make it unique to the species are a hard exoskeleton made of chitin; the body has three segments head, thorax, and abdomen, six legs, a pair of an antenna at the head and compound eyes. Insects are a more widespread group of animals. Its population is between six to ten million and accounts for half of all living creatures. Insects form about 90% of all animals on the earth.

Insects exist in all environments, whether land, freshwater, or marine life. Most of the organisms reside on land and freshwater while fewer species in seas and oceans. All insect starts their life from the hatching of eggs. The development stages start from the exoskeleton, and a series of its molts called molting. Insect pass through either three-stage metamorphism or four-stage metamorphisms. The third stage metamorphism lacks the pupa stage. The insects are thought to be evolved with the flowering plants.

Insects move in three ways: by walking, swimming, or flying. Insects are those invertebrates who have evolved the feature of flying with wings. Some insects spend their whole life underwater. Insects live as single while some of them reside in social groups like bees, flies, ants, and termites. In the human area, insects are a pest, eradicated by insecticides. But the fact is insects are useful in many aspects. They are a source of pollination in flowering plants.

What are Arachnids?

Arachnid is a Greek word thought to be organized from a myth. The myth is stated as human weaver Arachne was turned into a spider by God. Arachnids belong to subphylum Chelicerata classified in Arachnida class. Arachnids are small invertebrates with jointed legs. These animals have four pairs of legs. Some species can develop front pairs of legs as sensory function; in some species, the appendages even grow large. These jointed appendages give an appearance of extra legs. The most significant order of the Arachnida class is a spider.

The body of arachnids has two parts cephalothorax and abdomen. Arachnids lack wings. However, some species can fly with the wind with the help of silk fibers. Some species use silk as a weapon to catch prey or apply it for their reproduction. Arachnids lay eggs, the babies grow slowly and look like the adults. Arachnids have a hard exoskeleton made of resistant material chitin. Arachnids can reside in all habitats. Most species live on land, and some are inhabitants of the water. Arachnids can eat all things, liquid, and solid food. They are predators of the body juices of the prey.

Key Differences

  1. Insects are small creatures that vary in length, whereas arachnids are small, crawling creatures that belong to arthropods.
  2. The insect is a term that originated in the Latin language; conversely, arachnids is a Greek word.
  3. Insect possesses compound eyes; on the other hand, arachnids have simple eyes.
  4. An insect is recognized as having a pair of antennae, while arachnids lack antennae.
  5. Insects have three pairs of legs; on the flip hand, there are four pairs of legs in arachnids.
  6. Insects have three body parts head, thorax, and abdomen, whereas arachnids have two body segments cephalothorax and abdomen.
  7. Most of the insects have wings that help them to fly; conversely, arachnids do not have wings.
  8. Insects have pairs of appendages near their mouth; on the flip side, arachnids have pairs of appendages near mouth named Chelicerae.
  9. Insects pass through complete series of metamorphism; on the other hand, arachnids pass through the series of molts, and the process of metamorphism is not complete.
  10. Insects belong to class Insecta; conversely, arachnids are members of Arachnida class.
  11. The insect has millions of species; on the flip side, arachnids have about a lac species.
  12. Insects are widespread in all types of habitat; conversely, arachnids are mostly terrestrial.
  13. Insects respire through trachea; on the other hand, arachnids respire via trachea and book lungs.
  14. Insects own colorless blood; on the contrary, arachnids have blue-colored blood.
  15. Insects are categorized as flies, butterflies, and fleas; on the other side, arachnids are categorized as ticks, mites, and spiders.


Insects and Arachnids are both invertebrates belong to phylum arthropods. Insects are small animals with three body segments and have wings to fly. Arachnids have two body segments and do not have wings.

Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White