Nighthawk, 54, 198, figure 29, p. 36; figure 30, 

 p. 36; figure 73, p. 82; and figure 74, p. 

 82 



"Nuptial dress," erroneous theory of, 4, 5 

 Nuthatch, 49, 78, 115, 116 

 Nymphalis bolina. See Butterflies 



0 



Obliterative Coloration 



animals which form exceptions to general 

 rule of, 126; combined with background- 

 picturing in birds, 33-71; cooperation of 

 markings with, 30-32 ; erroneous theory of, 

 28; experimental demonstration of, 136; 

 inversion of, 124, 147; law of, 27; per- 

 fection of, in butterflies, 231; principles 

 of, 1 4-2 1 ; unaccompanied by obliterative 

 shading, 196 



See also Counter-Shading and Irides- 

 cence 



Ocellus. See Markings 

 Ocelot, 132, 175 

 Old Squaw. See Duck 

 Opossum, 119 



Optical illusion, the basis of protective color- 

 ation, 3 

 Orang-outan, 122 

 Ornithorhynchus paradoxus, 122 

 Otter, 119, 130 

 Ounce, 135, 141 



Outline concealment, natural devices for ac- 

 complishment of, in animals, 95 seq., 

 227 



Owl 



American great horned, 41, figure 36, p. 

 41; European eagle, 41; great gray, 41; 

 lapp, 41; long-eared, figure 37, p. 42, and 

 figure 38, p. 42; short-eared, figure 48, 

 p. 46; screech, 41, 42, 100; snowy, 114, 

 151. i5 2 



Owl Butterfly. See Butterfly, Calligo eury- 

 lochus 



Oyster-catcher, 27, figure 62, p. 78 



Paca. See Lape 

 Pangolin, 125 



Pantaloons (leg-feathers). See Appendages 



Papilionidce. See Butterflies 



Parrakeet, 27 



Parrot, 27, 108, 167 



Partridge, 13 



Patterns 



axiom of, 80; obliterative principles of, 

 9, 77-80; background picture, see Back- 

 ground-picturing Patterns 



Dewdrop 



butterflies, 229, 230; spiders, 210 



Flight 



of butterflies, 222—224; of moths, 233 



Patterns — Continued 

 Flower 



of butterflies, 216, 220, 228, figure 128, p. 

 216, figure 129, p. 216; humming-birds, 

 103 ; spiders, 210 

 Hiding 



of butterflies, 216, 217, 219, 225; of locusts, 



199; of moths, 225 

 Hole-picturing 



of caterpillars, 195; leopards, 133; owls, 



158; raccoon, 157 ; sloth, 125 ; sphinx-moth 



larva, 125; spiders, 211; whip-poor-will, 



158, figure 131, p. 216 

 Leaf vein 



of caterpillars, 185 

 Ruptive 



concealing principles of, 77, 78, 79, no; 

 of ant-eaters, 126; bees, 205; beetles, 201 ; 

 butterflies, 228; ducks, 65, 78; gannets, 

 155; grasshoppers, 199; kingfishers, 155; 

 locusts, 198; magpies, 115; moths, 236; 

 nuthatches, 115; ospreys, 155; pelicans, 

 155; plover, 79; prongbucks, 145; quail, 

 79; skunks, 123, 1 5 1 ; tanagers, in; tit- 

 mice, 115; trogons, 110, in ; wolverines, 

 123 

 Secant 



concealing principles of, 77, 78; of am- 

 phibians, 182; ant-eaters, 126; batrachi- 

 ans, 181; ducks, 78; frogs, 78; harnessed 

 antelope, 143; Hymenoptera, 204, 205; 

 koodoo, 142; Livingstone's eland, 142; 

 mackerel, 162; moths, 236, 239 ; sparrows, 

 78; squirrels, 143; toads, 78; zebras, 138, 



!39. 143 

 Variable 



ptarmigans, 45 

 See also Markings 

 Peacock 



See Frontispiece; concealing effect of tail 

 of, 95, and legend of Frontispiece ; obliter- 

 ative iridescence of, 88, 244 

 Pelican, 155 



Perspective, of animal patterns. See Back- 

 ground-picturing Patterns 

 Petrel, 75 

 Phalanger, 119 

 Pheasants 



concealing effect of tails of, 95, 97, figure 



133, p. 230; ocelli of, 229 

 Pierina. See Butterflies 

 Pigmentation in caterpillars, 187 notes 

 Pintail. See Duck 

 Pipe-fish, 167 

 Pipit, 45 

 Plaice, 164 



Plant Lice. See Aphides 



Plover, 52, 53, 79, figure 51, p. 48; figure 52, p. 

 48; figure 67, p. 81 ; figure 68, p. 81 ; figure 

 70, p. 82; figure 71, p. 82; and figure 72, 

 p. 82 



Polliwog, 169 



258 



