ECOS Guide to the Ecology of the Northern Rockies
 
   
 

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.


From  http://www.invasive.org/weeds/knapweed/chapter2.html

 

Exoskeleton – All insects, as well as all arthropods, wear their skeletons on the outside of their body.

Head – The head of an insect contains the brain, antennae, compound eyes and mouthparts.

Antennae – Antennae are used as feelers, for smelling and in some cases, hearing.

Mouthparts – 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:


Peter Wirtz, , Bugwood.org


Forestry Archive, Pennsylvania Department of Conservation and Natural Resources, Bugwood.org


Edward L. Manigault, Clemson University Donated Collection, Bugwood.org

 

Chewing mouthparts:


J.R. Baker & S.B. Bambara, North Carolina State University, Bugwood.org


John Moser, USDA Forest Service, Bugwood.org


Phillip Roberts, University of Georgia, Bugwood.org

 

Thorax – 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.

Wings – Insects may have 0, 1 or 2 pairs of wings.  Immature insects that go through simple metamorphosis will have small wing pads.

No Wings:


Susan Ellis, , Bugwood.org

 

 

1 Pair of Wings:


Forestry Archive, Pennsylvania Department of Conservation and Natural Resources, Bugwood.org

 

2 Pairs of Wings:


Edward L. Manigault, Clemson University Donated Collection, Bugwood.org

 

An immature true bug with wing pads:


Gary Bernon, USDA APHIS, Bugwood.org

 

Abdomen– 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.

 

 
The ECOS program is sponsored by the University of Montana's Division of Biological Sciences, and the College of Forestry and Conservation. Carol Brewer Program Director, Division of Biological Sciences. Paul Alaback Program Co-Director, College of Forestry and Conservation.
NSF LogoECOS is supported by the GK-12 Program of the National Science Foundation.
Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the National Science Foundation.