VOL VI 



INVERTEBRATE ANIMALS 



CHAPTER I 

 THE JOINTED ANIMALS Subkingdom ARTHROPODA 



THE INSECTS Class Insecta 

 ANTS, WASPS, BEES, ETC. Order HYMENOPTERA 



Distinction * N THE ear ly days of zoological science, when the value in classifi- 



between cation of the structural and embryological characteristics of living 



Vertebrates beings was but little understood, the animal kingdom was divided 



and Invert- i n t o two subkingdoms called Vertebrata and Invertebrata; the former 



embracing those forms provided with a vertebral column, or backbone, 



and the latter those that were not so provided. With the addition of some few 



classes, whose organization has only recently been fully comprehended, the Chor- 



data of to-day are coextensive with the Vertebrata of half a century ago. But the 



term Invetebrata, as denoting a natural assemblage of animals, has long ceased to 



be used by every competent zoologist, and is nowadays merely applied as a con- 



(2963) 



