For the relationship of the Coleoptera to other orders of insects see Hexapoda.
A true insect, or member of the class Hexapoda, may be known by the grouping of its body-segments in three distinct regions - a head, a thorax and an abdomen - each of which consists of a definite number of segments.
The compound eyes of insects resemble so closely the similar organs in Crustaceans that there can hardly be reasonable doubt of their homology, and the primitively appendicular nature of the eyes in the latter class suggests that in the Hexapoda also they represent the appendages of an anterior (protocerebral) segment.
From these three pairs of thoracic legs comes the name - Hexapoda - which distinguishes the class.
And the wings, though not always present, are highly characteristic of the Hexapoda, since no other group of the Arthropoda has acquired the power of flight.
