For many people, all small animals, be they slugs, earthworms, spiders, centipedes, woodlice, ladybugs or ants, can be categorized indiscriminately. tote: bugs! However, when we look at them a little more closely, we quickly realize that these little animals are not all the same. Some are insects, some are not. With a minimum of knowledge, it becomes easy to recognize them.
Like woodlice, millipedes, spiders and scorpions, insects belong to a very large group of animals called Arthropods . They were given this name because they have articulated legs when they are adults (arthropods means articulated feet ). And, like other arthropods, species belonging to the Insect class have an exoskeleton , or external skeleton. This exoskeleton constitutes a kind of shell that protects them against impact, injury and desiccation. Because they do not have a backbone, arthropods are part of the group of Invertebrates .
Other small animals are not part of the Arthropod group. Thus, the earthworm, or earthworm, has a body composed of a large number of segments, but it is devoid of legs; it is an Annelid. As for the snail, which has an unsegmented body, it is a Mollusc!