TABLE OF CONTENTS 



PART I. MORPHOLOGY AND PHYSIOLOGY 



PAGB 



POSITION OF INSECTS IN THE ANIMAL KINGDOM ..... 1 



RELATIONS OF INSECTS TO OTHER ARTHROPODA ..... 2 



The Crustacea 4 



The Merostomata 5 



The Trilobita 5 



The Arachnida 6 



Relations of Peripatus to insects 9 



Relation of Myriopods to insects . . . . . . . .11 



Relations of the Symphyla to insects 18 



Diagnostic or essential characters of Symphyla 22 



INSECTA (HEXAPODA) ........... 26 



Diagnostic characters of insects 26 



1. EXTERNAL ANATOMY 



a. Regions of the body 27 



b. The integument (exoskeleton) 28 



Chitin 29 



c. Mechanical origin and structure of the segments (somites, arthro- 



meres, etc.) 30 



d. Mechanical origin of the limbs and of their jointed structure . 35 



THE HEAD AND ITS APPENDAGES ........ 42 



a. The head 42 



The labrum .... ..... 42 



The epipharynx and labrum-epipharynx ..... 43 



Attachment of the head to the trunk . . . . .46 



The basal or gular region of the head 46 



The occiput . . . . . . ' . . . .48 



The tentorium 49 



Number of segments in the head ...... 50 



The composition of the head in the Hymenoptera ... 55 

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