PART I. MORPHOLOGY AND PHYSIOLOGY
PAGE POSITION OF INSECTS IN THE ANIMAL KINGDOM 1
RELATIONS OF INSECTS TO OTHER ARTHROPODA 2
The Crustacea 4 The Merostomata 5 The Trilobita 5 The Arachnida 6 Relations of Peripatus to insects 9 Relation of Myriopods to insects 11 Relations of the Symphyla to insects 18 Diagnostic or essential characters of Symphyla 22
INSECTA (HEXAPODA) 26
Diagnostic characters of insects 26
1. EXTERNAL ANATOMY
_a._ Regions of the body 27
_b._ The integument (exoskeleton) 28
Chitin 29
_c._ Mechanical origin and structure of the segments (somites, arthromeres, etc.) 30
_d._ Mechanical origin of the limbs and of their jointed structure 35
THE HEAD AND ITS APPENDAGES 42
_a._ The head 42
The labrum 42 The epipharynx and labrum-epipharynx 43 Attachment of the head to the trunk 46 The basal or gular region of the head 46 The occiput 48 The tentorium 49 Number of segments in the head 50 The composition of the head in the Hymenoptera 55
_b._ Appendages of the head 57
The antennæ 57 The mandibles 59 The first maxillæ 62 The second maxillæ 68 The hypopharynx 70 Does the hypopharynx represent a distinct segment? 82
THE THORAX AND ITS APPENDAGES 86
_a._ The thorax: its external anatomy 86
The patagia 89 The tegulæ 89 The apodemes 92 The acetabula 94
_b._ The legs: their structure and functions 95
Tenent hairs 99 Why do insects have but six legs? 100 Loss of limbs by disuse 101
_c._ Locomotion (walking, climbing, and swimming) 103
Mechanics of walking 103 Locomotion on smooth surfaces 111 Climbing 116 The mode of swimming of insects 116
_d._ The wings and their structure 120
The veins 121 The squamæ 123 The halteres 124 The thyridium 124 The tegmina and hemelytra 124 The elytra 124
_e._ Development and mode of origin of the wings 126
Embryonic development of the wings 126 Evagination of the wing outside of the body 132 Extension of the wing; drawing out of the tracheoles 133
_f._ The primitive origin of the wings 137
The development and structure of the tracheæ and veins of the wing 144
_g._ Mechanism of flight 148
Theory of insect flight 150 Graber’s views as to the mechanism of the wings, flight, etc. 153
THE ABDOMEN AND ITS APPENDAGES 162
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
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 Musculature of a beetle 213 Minute structure of the muscles 215 Muscular power of insects 217
THE NERVOUS SYSTEM 222
_a._ The nervous system as a whole 222
_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 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
_e._ The supraspinal cord 240
_f._ 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 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
_b._ The organs of smell 264
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
_c._ The organs of taste 281
Structure of the taste organs 282 Distribution in different orders of insects 282 Experimental proof 286
_d._ The organs of hearing 287
The ears or tympanal and chordotonal sense-organs of Orthoptera and other insects 288 Antennal auditory hairs 292 Special sense-organs in the wings and halteres 293
_e._ The sounds of insects 293
THE DIGESTIVE CANAL AND ITS APPENDAGES 297
_a._ The digestive canal 302
The œsophagus 303 The crop or ingluvies 303 The “sucking stomach” or food-reservoir 305 The fore-stomach or proventriculus 306 The œsophageal valve 311 Proventricular valvule 313 The peritrophic membrane 313 The mid-intestine 314 Histology of the mid-intestine 316 The hind-intestine 316 Large intestine 316 The ileum 317 The gastro-ileal folds 317 The colon 317 The rectum 318 The vent (anus) 319 Histology of the digestive canal 320
_b._ Digestion in insects 324
The mechanism of secretion 326 Absorbent cells 328
THE GLANDULAR AND EXCRETORY APPENDAGES OF THE DIGESTIVE CANAL 331
_a._ The salivary glands 331
_b._ The silk or spinning glands, and the spinning apparatus 339
The process of spinning 340 How the thread is drawn out 343 Appendages of the silk-gland (Filippi’s glands) 345
_c._ The cæcal appendages 347
_d._ The excretory system (urinary or Malpighian tubes) 348
Primitive number of tubes 353
_e._ Poison-glands 357
_f._ Adhesive or cement-glands 360
_g._ The wax-glands 361
_h._ “Honey-dew” or wax-glands of Aphids 364
_i._ Dermal glands in general 365
DEFENSIVE OR REPUGNATORIAL SCENT-GLANDS 368
Eversible coxal glands 369 Fœtid glands of Orthoptera 369 Anal glands of beetles 372 The blood as a repellent fluid 374 Eversible glands of caddis-worms and caterpillars 375 The osmeterium in Papilio larvæ 377 Dorsal and lateral eversible metameric sacs in other larvæ 377 Distribution of repugnatorial or alluring scent-glands in insects 382
THE ALLURING OR SCENT-GLANDS 391
THE ORGANS OF CIRCULATION 397
_a._ The heart 397
The propulsatory apparatus 401 The supraspinal vessel 403 The aorta 404 The pericardial cells 405 Pulsatile organs of the legs 405
_b._ The blood 407
The leucocytes 407
_c._ The circulation of the blood 409
Effects of poisons on the pulsations 412
THE BLOOD TISSUE 419
_a._ The fat-body 419
_b._ The pericardial fat-body or pericardial cells 420
Leucocytes or phagocytes in connection with the pericardial cells 421
_c._ The œnocytes 423
_d._ The phosphorescent organs 424
Physiology of the phosphorescence 426
THE RESPIRATORY SYSTEM 430
_a._ The tracheæ 431
Distribution of the tracheæ 432
_b._ The spiracles or stigmata 437
The position and number of pairs of stigmata 439 The closing apparatus of the stigma 441
_c._ Morphology and homologies of the tracheal system 442
_d._ The spiral threads or tænidia 444
_e._ Origin of the tracheæ and of the “spiral thread” 447
Internal, hair-like bodies 451
_f._ The mechanism of respiration and the respiratory movements of insects 451
_g._ The air-sacs 456
The use of the air-sacs 457
_h._ The closed or partly closed tracheal system 459
_i._ The rectal, tracheal gills, and rectal respiration of larval Odonata and other insects 463
_j._ Tracheal gills of the larvæ of insects 466
Blood-gills 475
_k._ Tracheal gills of adult insects 476
THE ORGANS OF REPRODUCTION 485
_a._ The male organs of reproduction 494
The testes 495 The seminal ducts 496 The ejaculatory duct 497 The accessory glands 497 The spermatozoa 497 Formation of the spermatozoön 498
_b._ The female organs of reproduction 500
The ovaries and the ovarian tubes 500 Origin of incipient eggs in the germ of the testes 504 The bursa copulatrix 505 The spermatheca 506 The colleterial glands 506 The vagina or uterus 507 Signs of copulation in insects 507