4 o THE STUDY OF INSECTS 



We have divided the Ilexapoda in this work into twenty-five orders 

 and have arranged them in a linear series as must be done in a simple 

 text-book; for it is impossible to indicate in a satisfactory way either the 

 relation of the orders to each other or the relative rank of the orders. 

 An effort is made to place near together closely allied orders, and to 

 treat first those that are more simple or primitive or generalized in 

 structure, and last those that are more specialized. But this plan could 

 be fully carried out only by having several parallel columns on the pages 

 of the book, each representing a distinct line of descent, an arrangement 

 which, to say the least, is impracticable. 



The list below indicates the sequence in which the orders are discussed 

 in the following chapters. 



subclass apterygota. — Wingless insects in which the wingless condition is 

 believed to be a primitive one, there being no indication that they have descended from 

 winged ancestors. 



1. order thysanura. — The Bristle-tails, p. 45 



2. order collembola. — The Spring-tails, p. 47 



subclass pterygota. — Winged insects and wingless insects in which the wing- 

 less condition is believed to be an acquired one; i.e., those insects that have de- 

 scended from winged ancestors. 



3. order orthoptera. — The Cockroaches, Crickets, Grasshoppers, and others. 



P- 49 



4. order zoraptera. — The genus Zorotypus. p. 62 



5. order isoptera. — The Termites or White Ants. p. 63 



6. order neuroptera. — The Dobson, Aphis-lions, Ant-lions, and others, p. 66 



7. order ephemerida. — The Mayflies, p. 74 



8. order odonata. — The Dragonflies and the Damselflies. p. 77 



9. order plecoptera. — The Stonefhes. p. 81 



10. order corrodentia. — The Psocids. p. 83 



11. order mallophaga. The Bird-lice. p. 85 



12. order embiidina. — The Embiids. p. 87 



13. order thysanoptera. — ■ The Thrips. p. 89 



14. order anoplura. — The Lice. p. 92 



15. order hemiptera. — The True Bugs. p. 94 



16. order homoptera. — The Cicadas, Leafhoppers, Aphids, Scale-bugs, and others. 



p. 109 



17. order dermaptera. — The Earwigs, p. 125 



18. order coleoptera. — The Beetles, p. 127 



19. order strepsiptera. — The Twisted Winged Insects, p. 176 



20. order mecoptera. — The Scorpion-flies, p. 178 



21. order trichoptera. — The Caddice-fties. p. 180 



22. order lepidoptera. — The Moths, the Skippers, and the Butterflies, p. 183 



23. order diptera. — The Flies, p. 286 



24. order siphonaptera. — The Fleas, p. 326 



25. order hymenoptera. — The Bees, Wasps, Ants, and others, p. 329 



TABLE FOR DETERMINING THE ORDERS OF THE HEXAPODA 



This table is merely intended to aid the students in determining to which of 

 the orders a specimen that he is examining belongs. No effort has been made to 

 indicate in the table the relation of the orders to one another. 

 A. Winged. (The wing-covers, Elytra, of beetles and of earwigs are wings.) 

 B. With two wings. 



C. Wings horny, leathery, or parchment-like. 



D. Mouth-parts formed for sucking. Wings leathery, shortened, or mem- 

 branous at the tip. p. 94 Hemiptf.ra 



DD. Mouth-parts formed for biting. Jaws distinct. 



