xii TEXT-BOOK OF ENTOMOLOGY 



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The pigment 253 



The basilar membrane 263 



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 move- 

 ments 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 t 268 



Relation of insects to smelling substances before and after the 



loss of their antennae 269 



Experiments on the use of the antennae in seeking for food . 270 

 Experiments testing the influence of the antennas 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 Orthop- 



tera 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 oesophagus 303 



The crop or ingluvies 303 



The " sucking stomach " or food-reservoir .... 305 



The fore-stomach or proventriculus 306 



The oesophageal valve 311 



Proventricular valvule ........ 313 



The peritrophic membrane 313 



The mid-intestine 314 



Histology of the mid-intestine 316 



The hind-intestine 316 



Largo intestine 316 



The ileum 317 



The gastro-ileal folds 317 



The colon 317 



The rectum . 318 



