CLASSIFICATION 103 



the meal worm (a beetle) and carpet beetle, the black and red ants, 

 the cheese skipper (a fly), house fly, and stable fly, and the 

 clothes moth. The adults of these insects would unhesitatingly 

 be placed with their proper relatives by any one, — the ants in 

 one group, the beetles in another, etc., but a very close examina- 

 tion is necessary in many cases before we can actually determine 

 the correct position of an animal with regard to other kinds of 

 animals. 



General Knowledge of Principal Groups. — Thus far we have 

 discussed insects almost exclusively, although it has been neces- 

 sary for us to mention other animals, such as birds, horses, dogs, 

 cats, and man. That there is a very great difference between 

 insects and these other animals is quite obvious and even those 

 who have never studied the way animals are grouped are familiar 

 in a general way with the popular names applied to many of the 

 larger assemblages. Thus children speak of insects, worms, 

 fishes, reptiles, and birds without realizing the significance of 

 the terms. 



Structure and Life Histories in Classification. — The error 

 is commonly made of calling anything that resembles an earth- 

 worm in general appearance a worm, but we have seen that the 

 young of many insects, that is, larvae, are wormlike. These 

 larvae are commonly called worms, but of course are very far 

 removed from the earthworm in the scale of life, since they later 

 become highly organized insects, whereas the earthworm re- 

 mains a worm as long as it lives. A comparison between the 

 structure of the earthworm and the insect larva would reveal 

 many fundamental differences, and a study of their life histories 

 would quickly prove that the two are really very distant relatives. 

 This shows that we must be acquainted with both an animal's 

 structure and its life history before we can be certain of its rela- 

 tions to other animals. 



System of Classification Used by Scientists. — The system of 

 classification now in use was devised by the Swedish naturalist 

 Linnaeus (1707-1778). He divided the animal kingdom into a 



