| Chapter III. The Distribution of Sexes | 5900 |
| Chapter XII. The Halicti: a Parasite | 6394 |
| Chapter VIII. Parasites | 6311 |
| Chapter IX. The Theory of Parasitism | 7145 |
| Chapter X. The Tribulations of The Mason Bee | 8035 |
| Chapter III. Another Prober (Perforator) | 6944 |
| Chapter XVI. A Parasite of The Maggot | 7315 |
