THE MORPHOLOGY OF INSECT SENSE ORGANS AND 

 THE SENSORY NERVOUS SYSTEM 



"By R. E. SNODGRASS 

 bureau of entomology 



CONTENTS 



PAGE 



Introduction 2 



I. The nervous system of insects 3 



The origin of nervous tissue 3 



The structure of nervous tissue 5 



The ventral nervous system 7 



The body ganglia 7 



The brain and its nerves 9 



The suboesophageal ganglion 13 



The stomatogastric nervous system 14 



The origin of the sensory nerves 16 



II. The peripheral endings of the sensory nerves 18 



The sensory innervation of the hypodermis 19 



The sensory innervation of the alimentary canal 21 



III. The general structure and classification of insect sense organs 23 



The structure of the body wall and its appendages 24 



Sensory hairs 25 



Sensory hairs with subhypodermal sense cells 26 



Sensory hairs with intrahypodermal sense cells 27 



The fundamental structure of an insect sense organ 28 



Classification of insect sense organs 30 



The sense cell 30 



The reception of sensory stimuli 33 



The sense rods, or scolopalge 35 



The axial fiber 40 



IV. The hair organs 40 



Sensilla trichodea 41 



, Sensilla chaetica 42 



Sensilla squamiforma 43 



Sensilla basiconica 43 



Sensilla coeloconica 44 



Sensilla ampullacea 45 



V. The campaniform organs 45 



VI. The plate organs 50 



VII. The chordotonal organs 55 



VIII. The organ of Johnston 64 



IX. The eyes 68 



The compound eyes 69 



The ocelli 72 



Postscript 75 



Abbreviations used on the figures yd 



References yj 



Smithsonian Miscellaneous Collections, Vol. 77, No. 8 i 



