Insect Head

1. The Insect Head
1. Introduction
In most insects, the head is a almost completely sclerotized compact sturdy compartment that houses the brain, a mouth opening, mouthparts used for ingestion of food, and major sense organs (including antennae, compound eyes, and ocelli).  Embryological evidence suggests that the first six body segments (three pre-oral and three post-oral) of a primitive worm-like ancestor may have fused to form the head capsule of most present-day insects.
The surface of the head is divided into regions (sclerites) by a pattern of shallow grooves (sutures).  The uppermost sclerite (dorsal surface) of the head capsule is known as the .  A suture usually runs along the midline of the vertex and splits into two frontal suture as it extends downward across the front of the head capsule.  The triangular sclerite that lies between these frontal sutures is called the frons.  The epistomal suture is a deep groove that separates the base of the frons from  a rectangular sclerite on the lower front margin of the head capsule.
The genas ("cheeks") are lateral sclerites that lie behind the frontal sutures on each side of the head.  Below each gena there may be another sclerite (the subgena), separated from the gena by a subgenal suture  A pair of compound eye, sockets for two antenae, and one or more ocelli (simple eyes) also may be found on the front, top, or sides of an insect's head.
Inside the head, an endoskeletal structure called the tentorium serves as an internal "truss" that reinforces the head capsule, supports the brain, and provides a rigid origin for muscles of the mandibles and other mouthparts.