Archetype

Homology Weekly: Clypeus

Tetraponera aethiops worker showing the location of the clypeus in green (Scanning Electron Micrograph, Roberto Keller/AMNH)

When looking at an arthropod from our vertebrate perspective it is easy to forget that we are looking right at the animal’s skeleton. While our own vertebrate skeleton consists of a series of internal compact pieces with sponge-like cores that support an external layer of muscles and entrails (all nicely wrapped in skin), the reverse is true for arthropods. The arthropod skeleton consists of a series of external plates and hollow tubes that form enclosed spaces within which the internal musculature system attaches¹. One consequence of this peculiar body architecture is that most of what we see on the outer surface of this exoskeleton is but a reflection of what is going on on the inside– minute external pits correspond to places where the cuticle folds in to form internal pillars, and innocent looking shallow furrows on the surface are large internal walls where powerful muscles originate. A simple examination of the exoskeleton, therefore, can tell us a lot about particular functions and consequently about an insect’s behavior. › Continue reading

Tags: Acanthoponera, Cibarium, Clypeus, Exoskeleton, Formica fusca, Labrum, Onychomyrmex, Tetraponera aethiops