PROC. ENT. SOC. WASH., VOL. 23, NO. 6, JUNE, 1921 139 



Fig. 5. Anterior end of mouth hook of first stage larva. 



Fig. 6. Second stage larva. 



Fig. 7. Anterior stigma and "felt-chamber" of second stage larva. 



Fig. 8. Posterior stigma and "felt-chamber" of second stage larva. 



Fig. 9. Mouth hooks or bucco-pharyngeal apparatus of second stage larva; 



m. h. lateral paired mandibular hooks. 

 Fig. 10. Third stage larva. 



Fig. 11. Anterior stigmata of third stage larva. 

 Fig. 12. Posterior stigmata of third stage larva. 



Fig. 13. Mouth hooks or bucco-pharyngeal apparatus ot third stage larva. 

 Fig. 14. Hypopharyngeal plates and inner surface of labium of third stage larva; 



h. p. hypopharyngeal plate; 1. labium. 

 Fig. 15. Epipharyngeal plate of third stage larva. 

 Fig. 16. Pupal respiratory apparatus; i. s. internal spiracle; p. c. prothoracic 



cornicle. 



Fig. 17. Tip of prothoracic cornicle of the pupa. 

 Fig. 18. Head of adult male. 

 Fig. 19. External genitalia of adult male. 

 Fig. 20. Hibernating second stage larva in a lobe of the fat body of the corn 



borer caterpillar; tr. tracheae of caterpillar. 



SOME NOTES ON THE TERMINAL ABDOMINAL STRUCTURES 



OF SAWFLIES. 



BY WILLIAM MIDDLETON, U. S. Bureau of Entomo/o^v. 



This paper, which was prepared under the direction of S. A. 

 Rohwer, at the Eastern Field Station, East Falls Church, 

 Virginia, and is a contribution from the Branch of Forest Insects, 

 IL S. Bureau of Entomology, deals with some of the terminal 

 abdominal structures of sawfly larvae and adults, and presents 

 a terminology to be used in future taxonomic papers. 



Postcornu. 



The larvae ot the wood, stem and grass boring sawrlies have 

 long been known to possess a single, heavily chitinized, terminal 

 appendage, or posterior horn, which until quite recently was 

 unnamed. This structure was called the postcornu by Cramp- 

 ton 1 and the term is adopted by the author. 



The postcornu in the internal feeding larvae is quite promi- 

 nent, occurring at the apex of the abdomen above the anal open- 

 ing upon a well defined told which is distinctly separated from 

 the dorsal plate, or epiproct, by lateral cauciad grooves. In 



'"The Genitalia and Terminal Abdominal Structures of Males and the 

 Terminal Abdominal Structure of the Larvae of "Chalastogastrous Hymenop- 

 tera" by G. C. Crampton, Proc. Knt. Soc. Wash., vol. 21, \o. 6, June, 1919, 



p. 137-8. 



