MORPHOLOGY OF THE INSECT ABDOMEN 



PART III. THE MALE GENITALIA 

 (INCLUDING ARTHROPODS OTHER THAN INSECTS) 



By R. E. SNODGRASS 

 Bureau of Entomology and Plant Quarantine, U. S. Department of Agriculture 



CONTENTS PAGE 



I. Introduction i 



Enumeration of the arthropod body segments 2 



Origin of the gonads and the gonoducts 7 



Evolution of the genital exit apparatus 14 



The external genitalia 18 



11. Onychophora 20 



III. Pycnogonida ( Pantopoda ) 23 



IV. Xiphosurida 25 



V. Eurypterida (Gigantostraca) 28 



VI. Arachnida 30 



VII. Crustacea 38 



VIII. Myriapoda progoneata 48 



IX. Chilopoda (Myriapoda opisthogoneata) 53 



X. Hexapoda 56 



Definitions of external genital structures of the male 62 



Collembola 65 



Protura 69 



Diplura and Thysanura 70 



Ephemeroptera ys 



Dermaptera 78 



Plecoptera 80 



Orthoptera 89 



References 90 



I. INTRODUCTION 



The series of papers entitled " Morphology of the Insect Abdomen " 

 is concluded with the present contribution. Other papers on the male 

 genitalia of insects, however, are designed to follow. The only excuse 

 here offered for the obvious fact that Part III, on the one hand, 

 greatly exceeds the scope of the general title, and, on the other, leaves 

 much to be said about insect genitalia, is the writer's conviction that 

 insects must be studied morphologically as arthropods — a practice at 

 least not prevalent among entomologists. The literature of entomo- 

 logical morphology is replete with long discussions on the nature and 



Smithsonian Miscellaneous Collections, Vol. 95, No. 14 



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