ANNALS 



OF 



The Entomological Society of America 



Volume XI 



JUNE, 19 18 



Number 2 



THE COMPARATIVE MORPHOLOGY OF THE 

 GENITALIA OF INSECTS.* 



Anna Grace Newell, Ph. D. 



I. Introduction. 



1. Somites. 



2. Theories and Investigators. 



3. Posterior Somites. 



II. Investigation. 



1. General Principles. 



2. Method of Preparation. 



3. Discussion and Tables: 



a. Thysanura. 



b. Orthoptera. 



c. Hemiptera. 



d. Neuroptera. 



e. Mecoptera. 



III. Summary. 



1. Somite Eight. 



2. Somite Nine. 



3. Somite Ten. 



4. Somite Eleven. 



IV. Bibliography. 



V. Explanation of Pl.^tes. 



VI. Plates. 



Genitalia. 



Cerci. 



Acknowledgr 





f. Trichopil^a. WAY " 3 192] 



g. Coleopt' 

 h. Lepidopt 

 i. Diptera. 

 ]. Hymenoptera. 



5. General Statement. 



6. Appendage I. 



7. Appendages II and III. 



8. Appendage IV. 



I. INTRODUCTION. 



1. Somites. — The third and caudal region of those into 

 which an insect is divided is called the abdomen. Here, for the 

 most part, the segments of which it is composed show a simple 

 and almost primitive structure. In the adult a typical segment, 

 more properly designated a somite, consists of a dorsal chitinized 

 portion or sclerite, called the tergum, and a ventral sclerite, or 

 sternum. These are connected laterally by arthrodial mem- 

 branes, conjunctiva or pleura, in each one of which is a spiracle. 

 There are exceptions to this arrangement at both cephalic and 

 caudal ends, with the greater complexity at the latter. No 



* Contribution from the Entomological Laboratories of the University of 

 Illinois, No. 51. ' 



109 



