| Chapter III. The Distribution of Sexes | 53 |
| Chapter XII. The Halicti: a Parasite | 48 |
| Chapter VIII. Parasites | 50 |
| Chapter IX. The Theory of Parasitism | 48 |
| Chapter X. The Tribulations of The Mason Bee | 120 |
| Chapter III. Another Prober (Perforator) | 46 |
| Chapter XVI. A Parasite of The Maggot | 54 |
