Abdomen

The abdomen is one of the three main body segments (or tagmata) of insects. The abdomen is the furthest posterior of the segments. In most insects clear segmentation can be seen in the abdomen. The abdomen contains the heart, reproductive organs, mid-gut and other digestive organs.

Definition from the Amateur Entomologists' Society: http://www.amentsoc.org/insects/glossary/terms/abdomen