Wikijunior:Bugs/Other Intro

There are other small animals commonly called "bugs" that aren't insects or arachnids. They are only loosely related to each other, and in fact, categorizing animals as "bugs" or "not bugs" is very bad way to categorize things. Scientists prefer to look at physical traits animals have in common, and at how their genes are related.

Some of the animals that are usually called "bugs", aside from insects and arachnids, are centipedes, millipedes, woodlice, and earthworms. Centipedes and millipedes look similar, and they're closely related to each other, being both called "myriapods". Centipedes and millipedes are both arthropods, like insects and arachnids. Woodlice are the small arthropods with round shells and many legs you might find living under bricks or logs. They're actually crustaceans, like crabs, shrimp, and lobsters. Finally, earthworms aren't even arthropods at all. Unlike the other creatures in this book, they don't have hard shells to protect them. Earthworms are annelids, a big group of worm-like animals which also includes leeches.

This section is for the "leftover" bugs – the bugs that aren't insects or arachnids. They don't have much in common, because they aren't really one group. They're more like a miscellaneous collection.