4 THE STUDY OF INSECTS. 



as red-oak, live-oak, and water-oak. All of the species of oak taken 

 together constitute the genus Quercus of botanists. Several species 

 of hawks and falcons are classed together by zoologists as the genus 

 Falco. 



The genera in turn are grouped into families. Thus the pines, 

 the spruces, and the larches resemble each other quite closely, and 

 are classed together as the Pine Family {Abietinece); the falcons, 

 hawks, kites, and eagles are classed together as the Falcon Family 

 (Falconidce). 



Closely-allied families are grouped together to form orders. The 

 Pine Family, the Cypress Family, and the Yew Family comprise the 

 Order Conifer a, or cone-bearing plants, of botanists. The Owl Fam- 

 ily {Strigida). the Falcon Family (Falconida:), and the Vulture Family 

 (Vulturidce) constitute the Order Rap/ores, or Birds of Prey. 



Closely-allied orders are grouped together to form classes. Thus 

 all the orders of birds taken together constitute the Class Aves or 

 Birds. 



The classes are grouped into branches, which are the principal 

 divisions of the Animal Kingdom.* In studying the different forms 

 of animals it is found that there are several distinct types of structure. 

 Some animals are built upon one plan or structure, and others on 

 other plans. All animals built on the same plan are said to belong to 

 the same Branch. Thus the back-boned animals comprise the Branch 

 Vertebrata ; the clams, oysters, snails, cuttlefish, and certain other 

 allied forms comprise the Branch Mollusca ; and the insects, spiders, 

 centipedes, lobsters, and their near relatives comprise the Branch 

 Arthropoda. 



All the branches of animals taken together constitute the Animal 

 Kingdom. 



It is not possible to lay down rules by which these different groups 

 of animals can be limited. For, as has been shown in our discussion 

 of species, all have been connected in past time by intermediate forms. 

 But notwithstanding this, each of the terms given above (Branch, 

 Class, Order, Family, Genus, and Species) expresses a pretty definite 

 conception, which the student will learn to comprehend by practice 

 in classifying animals. But the sequence in rank of these groups 

 should be learned at the outset. Beginning with the most compre- 

 hensive it is as follows : 



* The principal divisions of the Vegetable Kingdom are not termed 

 Branches ; hence we will not make further use of botanical illustrations in 

 this connection. 



