| Chapter III. The Distribution of Sexes | 5931 |
| Chapter XII. The Halicti: a Parasite | 6428 |
| Chapter VIII. Parasites | 6353 |
| Chapter IX. The Theory of Parasitism | 7175 |
| Chapter X. The Tribulations of The Mason Bee | 8065 |
| Chapter III. Another Prober (Perforator) | 6975 |
| Chapter XVI. A Parasite of The Maggot | 7347 |
