_f._ The primitive origin of the wings 137
The development and structure of the tracheæ and veins of the wing 144
Theory of insect flight 150 Graber’s views as to the mechanism of the wings, flight, etc. 153
The median segment 163 The cercopoda 164 The ovipositor and sting 167 The styles and genital claspers (Rhabdopoda) 176 Velum penis 181 The suranal plate 181 The podical plates or paranal lobes 182 The infra-anal lobe 183 The egg-guide 183
THE ARMATURE OF INSECTS: SETÆ, HAIRS, SCALES, TUBERCLES, ETC. 187
The cuticula 187 Setæ 188 Glandular hairs and spines 190 Scales 193 Development of the scales 195 Spinules, hair-scales, hair-fields, and androconia 197
Optical colors 201 Natural colors 203 Chemical and physical nature of the pigment 206 Ontogenetic and phylogenetic development of colors 207
Musculature of a caterpillar 213 Musculature of a beetle 213 Minute structure of the muscles 215 Muscular power of insects 217
The optic or procerebral segment 231 Procerebral lobes 232 The mushroom or stalked bodies 233 Structure of the mushroom bodies 234 The central body 237 The antennal or olfactory lobes (Deutocerebrum) 237 The œsophageal lobes (Tritocerebrum) 237
_c._ Histological elements of the brain 238
_d._ The visceral (sympathetic or stomatogastric) system 238
_f._ Modifications of the brain in different orders of insects 240
_g._ Functions of the nerve-centres and nerves 243
The simple or single-lensed eye (ocellus) 249 The compound or facetted eye (ommateum) 250 The facet or cornea 250 The crystalline lens or cone 251 The pigment 253 The basilar membrane 253 The optic tract 253 Origin of the facetted eye 255 Mode of vision by single eyes or ocelli 255 Mode of vision by facetted eyes 256 The principal use of the facetted eye to perceive the movements of animals 259 How far can insects see? 260 Relation of sight to the color of eyes 260 The color sense of insects 260
Historical sketch of our knowledge of the organs of smell 264 Physiological experiments 268 Relation of insects to smelling substances before and after the loss of their antennæ 269 Experiments on the use of the antennæ in seeking for food 270 Experiments testing the influence of the antennæ of the males in seeking the females 270 Structure of the organs of smell in insects 271