Orchids: --Dependence on insects, 144; strange mechanical adaptation; sweet-pogonia; perfume suggesting raspberries, 145; intention of the blossom, 146; adaptation for insects, 147; its fragrance a perfumed whisper of welcome, 148; a contrast, 172; form of invitation, 173; insect complement, 174; Arethusa bulbosa, 175; theories concerning the conveyance of the pollen, 176; the most highly specialized form of flowers, 180; distinguished by its structure; American varieties not air-plants; form of flower, 181; elasticity of the pollen of the _Spectabilis_, 182; self-fertilizing, 183; American and exotic species, 184; Arethusa's fragrance, 185; its structure, 186; significant depth of nectar wells; conditions demanded of insects, 187; Gray's surmise, 188; sphinx-moth its only complement, 190; manner of carrying the pollen by sphinx-moth, 193; extracting the pollen with a pencil; length of the nectary, 196; purple-fringed, 198; ragged, 200; very exceptional provision, 201; yellow-spiked, 203; moccasin-flower; ladies'-slipper; Venus's-slipper; the color of, 205; distinctive character of, 206; practical experiment, 209; imprisonment of the bee; manner of its release, 210; rattlesnake-plantain, 213; Angraecum, its long nectary, 219; tongue of a sphinx-moth eleven inches long, 220; nectary thirteen inches long, 223. "Origin of Species": --First important presentation of the theory of cross-fertilization, 105; tardy appreciation of the work, 115. _Odynerus flavipes_, wren-wasp, 10. Ovid, concerning hornets, 18. Parallels in Nature, 152. Platanthera, orchid group, 192. Pliny, 23. _Pogonia ophioglossoides_, sweet-pogonia, 145. Polistes, brown wasp, 161. Primrose, evening, 118. Psychid: --A sack-bearer; drags its house with it; feeds on seed-pods, 83; winter quarters of silk, 84. Queer Little Family: --Tree-hopper (_Membracis binotata_); a singular entertainment; graceful curves, 87; a branch in masquerade; queer thorns, 88; a sudden disappearance; animated thorns; like a covey of quails, 89; like "Bob White," 90; singular agility; queer anatomy; always ready for flight, 91; fondness for locust and oak-trees, simulating the color and character of the branches, 92; manner of sitting on the branches, 93; always headed towards the top; tiny tufts of cotton, 94; color and size of the tufts; a mere frothy shell; a riddle, 95; its relations, 96; an investigation, 97; its technique, 98; aerated cement; froth-house builder, 99; period of hatching, 100; a house for the winter; not a wanderer, 101. Ragged Orchid (_H. lacera_), 200. "Rattlesnake-plantain," 213. _Rudbeckia hirta_, cone-flower, 138.