Archetype

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.

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Tags: Acanthoponera minor, Aculeata, Apocrita, epinotum, Lasius (Acanthomyops) occidentalis, Manica rubida, Mesosoma, Propodeum, wasp waist

Homology Weekly: Tagmata

Profile view of a Ponera pennsylvanica worker showing primary tagmosis. Red: head; yellow: thorax; blue: abdomen (Scanning Electron Micrograph, Roberto Keller/AMNH)

When a group of successive segments along the arthropod body form a distinct section (by fusion, for example), the division is called a tagma (pl. tagmata). In the case of hexapods (= insects plus their primitively wingless cousins) the body segments are arranged into the three familiar tagmata: head, thorax and abdomen. › Continue reading

Tags: Abdomen, Alitrunk, Apocrita, Head, Mesosoma, Metasoma, Ponera, Tagma, Tagmata, Thorax