Insect external structure
Insect internal structure
Development of insects
Relationships of insects
Insect identification > Pterygota
The subclass Pterygota includes practically all our common insects and is the main branch of the class Hexapoda, the Apterygota, though of equal rank, being a mere twig in size in comparison.
As a whole the Pterygota are characterized by the presence of wings, though, as already indicated, many of them for one reason or another have lost these structures.
Almost all characters present in insects may be found in this section without referring to the Apterygota; practically all the pests and all the beneficial forms belong here; and their differences are so great that 23 orders have been established as subdivisions for them.
The earliest writers on insects did not regard these differences as of great importance and called the groups families or gave them even lower rank. More recent workers, however, have regarded them as of greater significance, some students of the subject being inclined to recognize more rather than fewer orders, and it is not at all unlikely that time will finally bring a general acceptance of 26 or 28 such groups instead of the first seven established by Linné or the 23 here treated.