TABLE OF CONTENTS xiii 



PAGE 



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 ctecal appendages 347 



d. The excretory system (urinary or Malpighian tubes) . . . 348 



Primitive number of tubes ....... 353 



e. Poison-glands 357 



/. 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 



Foetid 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 larvae ........ 377 



Dorsal and lateral eversible metameric sacs in other larvse . . . 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 supra-spinal 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 ceils ..... 420 



Leucocytes or phagocytes in connection with the pericardial 



cells 421 



