Head, thorax, abdomen

INVERTEBRATES. Invertebrates are all those animals that lack an internal skeleton (Endoskeleton).

ARTHROPODS. They are the invertebrates whose main characteristic is a body divided into segments and jointed legs. They are divided into: Myriapods, Crustaceans, Aracnidi.

INSECTS. They form the largest group in the whole Animal Kingdom. They are divided into two subclasses: Apterygota (that is, without wings) and Pterygota (that is, winged). The Pterygota are in turn subdivided into Holometabola (with complete metamorphosis) and Heterometabola (with incomplete metamorphosis; they lack the pupal stage). All insects have a body divided into three distinct regions or metameres.

HEAD: bears two “compound” eyes (made up of thousands of facets, called ommatidia; between them there may be two or three simple eyes called ocelli), the mouthparts and the antennae, which often perform sensory functions.

THORAX: is divided into pro-, meso-, metathorax; each of these segments bears a pair of legs. The wings, when present, two or four in number, are appendages of the II and III thoracic segments.

ABDOMEN: is generally divided into eleven segments, and the appendages it bears are often connected with the reproductive system; sometimes the abdomen carries real weapons of defence and attack, such as the sting of certain Hymenoptera.