Difference Between Spiders and Insects

Main Difference – Spiders vs Insects

Spiders and insects are two types of invertebrate animals that belong to the phylum Arthropoda. Therefore, both spiders and insects have jointed appendages. But, spiders belong to class Arachnida while insects belong to class Insecta. Hence, spiders and insects show distinct anatomical characteristics in their bodies. The main difference between spiders and insects is that the body of spiders is divided into two segments: cephalothorax and abdomen, whereas the body of insects is divided into three segments: head, thorax, and abdomen. Spiders have eight legs connected to the cephalothorax. They do not wings. Insects have six legs connected to the thorax. Their wings are also connected to the thorax.

Key Areas Covered

1. What are Spiders
     – Definition, Body Parts, Behavior, Examples
2. What are Insects
    – Definition, Body Parts, Behavior, Examples
3. What are the Similarities Between Spiders and Insects
     – Outline of Common Features
4. What is the Difference Between Spiders and Insects
     – Comparison of Key Differences

Key Terms: Arthropods, Head, Insects, Jointed Appendages, Spiders, thorax, Wings

What are Spiders

Spiders are a type of arachnids. Around 50,000 spider species can be found all over the world (except in Antarctica). The body of spiders is divided into two segments: cephalothorax and abdomen. Spiders may have up to eight, simple eyes. The eight pairs of jointed appendages or legs are connected to the cephalothorax. Cephalothorax consists of mouth fangs, brain, stomach, and glands, which produce poisons. The multiple eyes of a jumping spider are shown in figure 1.

Figure 1: Multiple Eyes of a Jumping Spider

The tiny, leg-ish structures that surround the mouth fangs are called pedipalps. They hold the prey. Spiders do not have wings. The abdomen of the spiders consists of a type of glands called spinneret from which silk is released to the outside. Most spiders make their webs. Spiders secrete oils to stick their body to the web. The hairs on the legs of the spiders are sensitive to vibrations and smells. Each leg consists of six joints. Therefore, spiders have 48 knees. A spider web is shown in figure 2.

Figure 2: Spider Web

Spiders undergo incomplete metamorphosis. The three stages of the life cycle of a spider are egg, larva/nymph, and adult. Spiders feed only on liquid food. Therefore, they have a tinny gut. Most spiders are predators who inject venom into the prey to kill it. However, there are herbivorous spiders as well.

What are Insects

Insects are a small type of invertebrate animals who are well adapted to their environment. They are relatively small in size. Around six to ten million insect species can be found in the world. Most insects live in terrestrial environments. The body of insects consists of three segments: head, thorax, and abdomen. The head consists of a pair of compound eyes and a pair of antennae. Typically, two pairs of wings are connected to the thorax. Three pairs of legs are connected to the thorax. The body is covered with an exoskeleton, which is made up of chitin. An insect is shown in figure 3.

Figure 3: Ant

Insects undergo complete metamorphosis. The four stages of the life cycle are egg, larva/nymph, pupa, and adult. The three types of feeding mechanisms of insects are chewing, sucking, and sponging. Chewing insects have mouthparts such as mandibles, maxilla, and labium. Sucking insects are called true bugs. Sponging insects secrete saliva on the solid food, and the solution is drawn up by the mouth.

Similarities Between Spiders and Insects

• Both spiders and insects are invertebrates that belong to the phylum Arthropoda.
• Both spiders and insects are mainly terrestrial.
• Both spiders and insects are triploblastic, haemocelomic animals with bilateral symmetry.
• Both spiders and insects are composed of joint legs.
• The body of both spiders and insects is segmented.
• Both spiders and insects are composed of a chitinous exoskeleton.
• Both spiders and insects consist of compound eyes and antennae.
• Both spiders and insects are air-breathing animals.
• Both spiders and insects are composed of a complete digestive system.
• Both spiders and insects are composed of an open circulatory system.
• Both spiders and insects are cold-blooded animals.
• The excretion of spiders and insects occurs through Malpighian tubules.
• The nervous system of both spiders and insects are composed of a brain and a ventral nerve cord.
• Both spiders and insects are unisexual animals, e. both sexes are separated.
• Females of both spiders and insects hatch

Difference Between Spiders and Insects

Definition

Spiders: Spiders are eight-legged, predatory arachnids, consisting of two body segments: cephalothorax and abdomen.

Insects: Insects are small arthropods who possess six legs and one or two pairs of wings.

Scientific Classification

Spiders: Spiders belong to the class Arachnida under the phylum Arthropoda.

Insects: Insects belong to the class Insecta under the phylum Arthropoda.

Habitat

Spiders: Spiders are mainly terrestrial.

Insects: Insects are mostly terrestrial. Some insects can be aquatic and parasitic.

Division of the Body

Spiders: The body of spiders is divided into cephalothorax and abdomen.

Insects: The body of insects is divided into head, thorax, and abdomen.

Appendages

Spiders: Spiders have four pairs of appendages.

Insects: Insects have three pairs of appendages.

Wings

Spiders: Spiders do not have wings.

Insects: Many insects have wings.

Mouthparts

Spiders: Spiders possess chelicerae.

Insects: Insects possess mandibles, proboscis, and maxilla.

Senses

Spiders: Spiders sense through their cuticles.

Insects: Insects have one pair of antenna.

Eyes

Spiders: Spiders have one to six pairs of simple eyes.

Insects: Insects have compound eyes.

Respiration 

Spiders: Respiration of spiders occurs through trachea and book lungs simultaneously.         

Insects: Respiration of insects occurs through the trachea.                           

Blood Color

Spiders: Spiders have blue color blood.

Insects: Insects have colorless blood.

Diet

Spiders: Spiders are mainly predators.

Insects: Insects feed on both plant and animal materials.

Metamorphosis

Spiders: Spiders undergo incomplete metamorphosis.

Insects: Insects undergo complete metamorphosis.

Examples

Spiders: Jumping spider, black widow spider, brown recluse spider, goliath birdeater, and tarantula are examples of spiders.

Insects: Butterfly, beetle, bee, ant, fly, termite, grasshopper, true bugs, and louse are examples of insects.

Conclusion

Spiders and insects are two types of arthropods, containing jointed appendages. The body of spiders is divided into two segments: cephalothorax and abdomen. However, the body of insects is divided into three segments: head, thorax, and abdomen. Spiders have eight legs while insects have six legs. Insects also have wings. Most of the spiders are predators. Insects may feed on both plant and animal materials. Hence, the main difference between spiders and insects is the anatomical structure of the body and diet.

Reference:

1.“KidZone Spider FactsThe Body of a Spider.” Worksheets for Kids, Available here.
2.“Basic Insect Anatomy.” Insect Identification, Available here.

Image Courtesy:

1. “Female Jumping Spider – Phidippus regius – Florida” by Thomas Shahan (CC BY-NC-ND 2.0) via Flickr
2. “918485” (CC0) via Pixabay
3. “40850” (CC0) via PEXELS

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