2 TEXT-BOOK OF ENTOMOLOGY 



prised under the term Metazoa are the Porif era, Coeleuterata, Vermes, 

 Echinodermata, Mollusca, Arthropoda, and Yertebrata. Their ap- 

 proximate relationships may be provisionally expressed by the fol- 

 lowing 



TABULAR VIEW OF THE EIGHT BRANCHES OR PHYLA OF THK 



ANIMAL KINGDOM. 

 VIII. Vertebrata. 



Ascidians and Fishes 

 to Man. 



VII. Arthropoda. 



Trilobites, Crustacea, Arachnids, 

 Insects, etc. 



VI. Mollusca. 



Clams, Snails, Cuttles. 



V. Echinodermata. 



Crinoids, Star-fish, Sea-urchin*, etc. 



r. Ve 



IV. Vermes. 



Flat and Round Worms, I'olyzoa, Brachiopods, Annelids. 



III. Ccelenterata. 



Hydra, Jelly-fishes. 



II. Porifera. 



Sponges. 



METAZOA. 



Many-celled animals with 8 cell-layers. 



I. PROTOZOA. 



Single-celled animals. 



RELATIONS OF INSECTS TO OTHER AKTHEOPODA 



The insects by general consent stand at the head of the Arthro- 

 poda. Their bodies are quite as much complicated or specialized, 

 and indeed, when we consider the winged forms, more so, than any 

 other class of the branch, and besides this they have wings, fitting 

 them for an aerial life. It is with little doubt that to their power of 

 flight, and thus of escaping the attacks of their creeping arthropod 

 enemies, insects owe, so to speak, their success in life ; i.e. their 

 numerical superiority in individuals, species, and genera. It is also 

 apparently their power of moving or swimming swiftly from one 

 place to another which has led to the numerical superiority in species 

 of fishes to other Yertebrata. Among terrestrial vertebrates, the 

 birds, by virtue of their ability to fly, greatly surpass in number of 

 species the reptiles and mammals. 



The Arthropoda are in general characterized by having the body 



