- Natural selection, the principle stated, 41-43; general acceptance of the theory of, 46; tabular demonstration of, 302; outline of theory of, 307; its effects on man and animals different, 311; hardly acts among civilized societies, 330; what it can not do, 333; cannot produce injurious or useless modifications, 334.
- Nectarineidæ, 254.
- Necydalidæ, mimic Hymenoptera, 96.
- Nemophas grayi, a Longicorn mimicked by a Longicorn, 95.
- Nests of Birds, why different, 215; of young birds, how built, 219; construction of, described by Levaillant, 224; imperfections in, 229; influenced by changed conditions and persistent habits, 232; classification of, according to function, 237.
- New forms, how produced by variation and selection, 286.
- New Guinea, relation of the several Papuan islands to, 194.
- Nocturnal animals, colours of, 51.
- Nomada, 98.
- Oberea, species resemble Tenthredinidæ, 96.
- Odontocera odyneroides, 96.
- Odontocheila, 97.
- Odyncrus sinuatus, 90.
- Onthophilus sulcatus, like a seed, 58.
- Onychocerus scorpio, resembles bark, 56.
- Orange-tip butterfly, protective colouring of, 59.
- Orchis, structure of an, explained by natural selection, 271.
- Orgyia antiqua and O. gonostigma, autumnal colours of, 62.
- Oriolidæ, 253.
- Ornithoptera priamus, 145, 173;
- O. helena, 173.
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