| Chapter I. The Terebinth Aphids. | 935 |
| Chapter II. Experiments | 885 |
| Chapter III. Exchanging The Nests | 524 |
| Chapter IV. More Enquiries Into Mason Bees | 1036 |
| Chapter V. The Story of My Cats | 926 |
| Chapter VI. The Red Ants | 778 |
| Chapter VII. Some Reflections Upon Insect Psychology | 1003 |
| Chapter VIII. Parasites | 615 |
| Chapter IX. The Theory of Parasitism | 650 |
| Chapter X. The Tribulations of The Mason Bee | 933 |
| Chapter XI. The Leucopses | 359 |
