TABLE OF CONTENTS. xv 



PAGE 



V. The Study of Myrmecophily 128 



VI. The Study of Ant Morphology 129 



VII. The Difficulties of Classification 129 



i. The Three Castes. 2. The Variability of Ants. 



VIII. The Anatomical Basis of Classification 131 



IX. Quadrinomial Nomenclature 131 



X. Conspectus of the Classification of Ants 134 



CHAPTER IX. 



THE DISTRIBUTION OF ANTS. 



I. Modes of Dissemination 145 



II. Two Methods of Studying Ant-distribution 146 



III. The Faunistic Distribution of Ants 147 



i. Geological Parallelism in the Origin and Distribution of 

 Ants and Mammals. 2. History and Distribution of the 

 Principal Groups. 3. The North American Ant-fauna. (a) 

 The Preglacial Fauna. (&) The Four Postglacial Waves 

 of Northward Migration. (c) The Four Centers of Redis- 

 tribution, (d) Adventitious Tropical and Subtropical Forms. 

 (c) Ants Imported by Commerce. (/) Conclusions. 



IV. The Ethological Distribution of Ants 156 



CHAPTER X. 



FOSSIL ANTS. 



I. Paleontological History of the Hymenoptera 160 



II. The Tertiary Ants 161 



i. Relations of the Extinct to the Living Genera. 2. Localities 

 Yielding Tertiary Ant Fossils. 3. Comparison of Lacustrine 

 with Amber Ants. 4. Inadequacy of Past Researches on 

 the Oeningen and Radoboj Ants. 5. Numerical Proportion 

 of Known Fossil Ant Specimens to Those of Other Hymen- 

 optera. 6. Relative Proportion of Fossil Ants in the Various 

 Subfamilies and Conclusions Based Thereon. 7. The Known 

 Genera of Amber Ants. 8. Causes of the Intermingling 

 of Arctic and Tropical Forms. 9. Remarks on Interesting 

 Genera and Species. 10. The Tertiary Ants of North 

 America. 



