What is an Insect?

From Wikipedia, the free encyclopedia
Insects, are a class in the phylum Arthropoda. They are small terrestrial invertebrates which have a hard exoskeleton.

A definition is a good starting point but you already know what an insect is, right? The problem begins when you try to distinguish between all those INVERTEBRATES that may look like an insect.

Let's back up and talk about Arthropods first.

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An Insect is...

They say a picture is worth a thousand words so how many words is a video worth?
http://biokeys.berkeley.edu/inverts/insect_anatomy.html

Insect Life Cycle

So insects develop through different stages until they become an adult. Here is an example of Complete Metamorphosis.
The stages are egg, larva, pupa, and adult.
The included photo does not show the egg stage.
"Ontwikkelstadia wespenpoppen" by Asaf at Dutch Wikipedia. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Ontwikkelstadia_wespenpoppen.jpg#/media/File:Ontwikkelstadia_wespenpoppen.jpg

Insect Life Cycle

Here is an example of Incomplete Metamorphosis.
The stages are egg, nymph and adult
The following illustration is from Wiki:"Grasshoppermetasnodgrass" by S.E. Snodgrass - Fig. 9 from Insects, their way and means of living, R. E. Snodgrass. Archive.org. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Grasshoppermetasnodgrass.svg#/media/File:Grasshoppermetasnodgrass.svg