TABLE OF CONTENTS xi 



PAGE 



The podical plates or paranal lobes ... ... 182 



The infra-anal lobe ... .... .183 



The egg-guide . . ...... 183 



THE ARMATURE OF INSECTS : SET^E, HAIRS, SCALES, TUBERCLES, ETC. . 187 



The cuticula . . '. ........ 187 



Setaj . ........... 188 



Glandular hairs and spines ......... 190 



Scales . . .... .193 



Development of the scales ......... 195 



Spinules, hair-scales, hair-fields, and androconia ..... 197 



THE COLORS OF INSECTS .......... 201 



Optical colors ........... 201 



Natural colors ........... 203 



Chemical and physical nature of the pigment ..... 206 



Ontogenetic and phylogenetic development of colors .... 207 



2. INTERNAL ANATOMY 



THE MUSCULAR SYSTEM . . . . . . . . .211 



Musculature of a caterpillar ......... 213 



Musculatui'e of a beetle ......... 213 



Minute structure of the muscles ......... 215 



Muscular power of insects . . . . . . . . ... 2J7.; 



THE NERVOUS SYSTEM .......... 



a. The nervous system as a whole ....... 22.2 



b. The brain .......... . 226' 



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 antenna! or olfactory lobes (Deutocerebrum) . . . 237 



The oesophageal lobes (Tritocerebrum) ..... 237 



c. Histological elements of the brain ....... 238 



d. The visceral (sympathetic or stomatogastric) system . . . 238 



f. The supraspinal cord ....... . 240 



/. Modifications of the brain in different orders of insects . . . 240 



g. Functions of the nerve-centres and nerves ..... 243 



THE SENSORY ORGANS .......... 249 



a. The eyes and insect vision ..... . 249 



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 



