Mesosoma

The mesosoma is the middle part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the metasoma.

In Apocrita Hymenoptera (wasps, bees and ants), it consists of the three thoracic segments and the first abdominal segment (the propodeum). In scorpions, it forms the main body, containing all of the major organs (lungs, digestive track and sexual organs).

In other arachnids such as spiders, the mesosoma is fused with the metasoma to form the opisthosoma.