Manica rubida
Homology Weekly: Gaster
The five segmented gaster (in yellow, arabic numeral) in a Cerapachys nitidulus worker. Roman numerals refer to abdominal segments (Scanning Electron Micrograph, Roberto Keller/AMNH)
Gaster is a morphological term that is very useful and yet imprecise for the purpose of comparative anatomy as it is currently used in ants. It comes from the Greek for “belly” and it refers to the collection of segments in the metasoma that remain after the pedicel of ants and wasps. It is the bulbous part of the body that hosts the insect viscera.
Homology Weekly: Propodeum
Abdomen of a Manica rubida worker. Roman numerals correspond to external abdominal segments. Propodeum shown in blue (Scanning Electron Micrograph, Roberto Keller/AMNH)
The propodeum is the subversive segment of the apocritan abdomen. As explained in a previous post, at some point during the evolution of Hymenoptera this first abdominal segment decided to part ways with its serial homologues and fuse with the thorax, forming a secondary tagma we call mesosoma. It is the Texas of the body’s segments so to speak.
