Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects. Although the three orders are sometimes grouped together in a class called Entognatha because they have internal mouthparts, they do not appear to be any more closely related to one another than they are to all insects, which have external mouthparts.
Isotoma anglicana (Entomobryomorpha) with visible furcula
Deutonura monticola (Poduromorpha)
A species of Sminthurinae (Symphypleona: Sminthuridae)
The abdomen is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. The area occupied by the abdomen is called the abdominal cavity. In arthropods, it is the posterior tagma of the body; it follows the thorax or cephalothorax.
The human abdomen and organs which can be found beneath the surface
(Left) Henry Gray (1825–1861). Anatomy of the Human Body. (Right) A male abdomen.
Side-by-side comparison of quadrants and regions.