—— at corresponding ages, [14], [86].
Insects, colour of, fitted for habitations, [84].
——, sea-side, colours of, [132].
——, blind, in caves, [138].
——, luminous, [193].
——, neuter, [236].
Instinct, [207].
Instincts, domestic, [213].
Intercrossing, advantages of, [96].
Islands, oceanic, [388].