VI CONTENTS. 



LETTER VI. 



The Mouth, of Insects.— The Proboscis of the Fly.— The 

 Members of Locomotion. — Wings; their Structure. — 

 Wonderful Eapidity of Flight. —Halteres or Poisers; 

 their Anatomy and supposed Function. — The Legs. — 

 Remarkable Organization of the Fly's Foot. — Repetition 

 of similar parts in the organs described page 4 



LETTER Vn. 



The Anatomy of the Fly. — Its Organs of Digestion; of 

 Circulation ; of Respiration. — ^Wonderful Structure of the 

 Spiracles, or Breathing-holes ; and Tracheae, or Respira- 

 tory Tubes. — ^Nervous System. — Considerations upon the 

 Nervous System of the House-fly, as compared with that 

 of its Larva and of the Worm 5 



LETTER Vin. 



Life-history of the Fly. — Organs of Reproduction. — Mode of 

 depositing its Eggs. — ^Table showing its remarkable Re- 

 productive Powers. — The Larva ; the Pupa ; Transforma- 

 tions. — The perfect Fly; its Habits. — Strange fatal 

 Disease to which it is subject. — Its uses as a sanatory 

 agent, &c. — Transformation of Matter in the Animal 

 Creation. — Reflections upon Geological Facts in con- 

 nexion with the Flv. — Conclusion ( 



