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External structure

Hello, welcome to Insect Anatomy ; External Structure. This is one of the many insect biology information pages that you can find here.


Here, we will find out what an insect's Exoskeleton is comprised of, the basic structure of an insects body, and the difference between an insects and arachnids body. We will also discuss the structure of the insect head. 


Insects, Arachnids, and Crustaceans are all Invertebrates, meaning they don't have a backbone. Also, they are all arthropods. Arthropods are invertebrates with a skeleton on the outside of their body. The technical term for this skeleton is an exoskeleton. They all are known to have segmented bodies. These three groups share similarities in that respect, but when it comes to body structure they are all different. I will show you the difference between an arachnid and insects body later on, but first let's discuss exoskeletons in more depth. 

Exoskeletons are the outer skeleton of an Insect, Arachnid, Crustacean.  The exoskeleton is made up of circular plates called Sclerites, which are  made from chitin. The exoskeleton itself covers the entirety of the body and consists  of.....

1. The Epidermis

2. The Procuticle

3. The Epicuticle

4. The Basement membrane. 

1. The Epidermis  is a secretory tissue that is accountable for creating the majority of the inner membrane.

2. The Procutile exists just above the Epidermis. It is made of microfibers, which are entwined in protein. 

3. The Epicuticle prevents water loss and stops foreign particles from entering the insect. It is situated on the outside of the cuticle. Within the Epicuticle, you will find lipoproteins and fatty acids.

4. The Basement Membrane is located at the bottom and provides the exoskeleton with extra support. 

Grean Bean Insect.jpg

1. The Head.

2. The Thorax

3. The Abdomen. 

Body example of arachnids.jpg

1. The Cephlthorax 

2. The Abdomen 

The Arachnid body

The Insect Head.

Antennae: Filiform( Threaded antennae.)



Mandibles and Maxilla.


Compound Eyes

Compound eyes consist of thousands of miniscule Ommatidia. These themselves contain a number of photoreceptor units. Within these Photoreceptor units, there is a cornea, lens, and photoreceptor cells. Photoreceptor cells are responsible for detecting colour and brightness in an insect's environment. 


If we take my Giant Asian Mantis,Moonlight, as an example, he has 3 to 4 Oceli, but some insects such as bees are known to have up to five. They are known as the'simple eyes' of an insect. These are generally located on the Vertex( the top of the head), or at the top of the frons( middle of an insects face). However, it has been known that these three shining dots can be found elsewhere on the body too. They are basic photoreceptors, which have a singular lense just like our eyes. However, the compound eyes are better than the Ocelli at sensing solid elements within the insect's environment. Ocelli are more useful for picking up movement. 

Cervix: The insects neck. It helps support the head. 


The Vertex is the top of the head and is separated by the Ecdysial Cleavage sutures, as seen in the diagram above.

Mandibles and Maxilla.

Mandibles and Maxilla are different parts entirely. However, they do have very similar functions, and therefore many people get confused between the two.


Mandibles: These are used to shred food apart. These are located just below the mouth. 




Maxilla:The maxilla are located behind the mandibles and are used to hold food in place, so that the mandibles can be ready to slice and dice the insects food. 






Insect anatomy external Henry.jpg

Antennae( Filiform):

There are many types of antennae which have different functions for different species of insects. In the diagram that I have devised, the antennae are filiform. 

The Front.

Anatomy Key:

A more detailed diagram is below. Unfortunately, the image I have above of Moonlight's head is not big enough to show insects true, amazing head structure. 



Key Features 

Compound Eye.


Cheeks. These are the lateral regions on insects face.

The Insect Body.

The Insect body is comprised of three main parts. These are: The Head, The Thorax, and the Abdomen. The thorax itself has three segments to it too: The Prothorax, The Mesothorax and the Metathorax.

A feature I have not mentioned is the Tentorium. It exists inside the insects head and its main role is to protect the brain and ensure the mouth is rigid on the insect. It is hard to spot, but it's an important part to mention. 

new insect head diagram.png



There are many types of insect antennae. Please see the different types listed below. 

Aristate: Pouch like with a lateral bristle extending outwards.

Moniform: Beaded Antennae. 

Serrate Appears like a saw

Filiform: Threadlike.

Pectinate: Comb like.

Plumose: Feather like.

Setaceous: Wide segments and clubbed at the end. 

Geniculate: It is straight and then elbow shaped at the end.


Stylate: Thick at the bottom and a bristle sticks outwards

Clavate:Wide segments and clubbed at the end. 

Lamellate: Flattened and nested tips, appears like a folded fan

anetnnae types.png

Basic Structure of an antennae.

1, Scape: The start of the antennae. It is the part that connects to the head, not the part pointing away.

2. Pedicle: The middle segment of the insect antennae. 

3. Flagellum: The rest and top of the antennae. Also known as flagemeres.

Insect anatomy external Henry.jpg

1. Scape

3. Flagellums or Flagemeres


General function of insect antennae

Many people assume insects antennae are just feelers and are for feeling around for their environment, however this couldn't be more further from the truth.


1. To gauge wingspeed whilst in flight. Flies have the ability to do this. 

2. To sense air humidity. Moths are known to do this.

3.To smell.

4. To taste.

5.To communicate with other insects in their species. 

6. Are used to detect sound. 


Thank you visiting  my page and I hope you have absorbed this useful information.


www. wikimedia. com for head structure of an insect and spider pic. 

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