Northern Rockies Natural History Guide
What is an Insect
Insects can be distinguished from other arthropods by the number of legs and distinct body parts. If you see an animal that has six legs and three main body parts (head, thorax and abdomen) you are looking at an insect. Many insects, but not all, also have wings and antennae.
Here are diagrams of some common insects with their body parts labeled. Below the diagrams are some descriptions of important insect characteristics.
All insects, as well as all arthropods, wear their skeletons on the outside of their body.
The head of an insect contains the brain, antennae, compound eyes and mouthparts.
Antennae are used as feelers, for smelling and in some cases, hearing.
Insects mouthparts are highly specialized for manipulating and consuming different types of foods. There are two main types of mouthparts: sucking and chewing.
Sucking Mouthparts
Chewing mouthparts
The thorax is the locomotion part of the insect. The six legs are connected to the thorax and if the insect has wings, they are also attached here.
Insects may have 0, 1 or 2 pairs of wings. Immature insects that go through simple metamorphosis will have small wing pads.
No Wings
1 Pair of Wings
2 Pairs of Wings
An immature true bug with wing pads
The abdomen is the third body part and is the place where reproductive organs are found as well as the place where most of the breathing, digestion and blood circulation takes place.