Gérard Filippi is a confirmed entomologist, therefore an expert in the study of insects. Some criteria common to all insects allow recognizing and differentiating them from other invertebrate groups. They have an external skeleton, also known as an exoskeleton and resembling the armor of a warrior, and several articulated appendages like their legs and antennae. Insects are divided into three segments: a head with simple and/or compound eyes, mouthparts, and one or two pairs of antennae; a thorax with three pairs of legs, one or two pairs of wings, and respiratory openings; and an abdomen carrying reproductive organs and sometimes eardrums. Their life is made up of different stages (egg, larva, nymph, imago) interspersed with molts.