Vol. XXVli] ENTOMOLOGICAL NEWS. 325 



EXPLANATION OF PLATE XVII. 



Figs, i, 2 and 10. Acanthagrion adustum, type $ and ?, Wismar, 

 British Guiana, Feb. 15, 1912. i and 2, appendages of $ ; 10, 

 portion of right dorsum of thorax of $ , showing the mesepis- 

 ternal fossa and mesostigmal lamina. 



Figs. 3, 4 and 7, appendages of $ of Acanthagrion indefcnsnm, type, 

 Wismar, British Guiana, Feb. 16, 1912; 7 posterior view. 



Figs. 5, 6, 8 and u. Acanthagrion kcitnedii, type $ and $, Cumuto, 

 Trinidad, March 10, 1912. 5, 6 and 8 , 8 posterior view; u $, 

 same as- 10. 



Figs. 9 and 12. Acanthagrion "gracile." 9, posterior view of $ , Morales, 

 Guatemala, 'May 27, 1909; 12, same as 10, $, Gualan, Guatemala, 

 June 10, 1909. 



Fig. 13. Acanthagrion ascendens. Same as 10, $, Georgetown, Brit- 

 ish Guiana, January 27, 1912. 



Notes on the Penes of Zygoptera (Odonata). 



No. 1. Species Limits in the Genus Acanthagrion. 

 By CLARENCE HAMILTON KENNEDY, Cornell University. 



(Plate XVIII) 



In the fall of 1913, when I was working with the Argias 

 and Ischnuras of Washington and Oregon 1 I discovered that 

 the penis, hitherto overlooked by systematists who had studied 

 the Zygoptera, was in some cases an excellent generic char- 

 acter and in other cases even a good specific differential. In 

 the Fall of 1914, when I was working over my collection of 

 California Odonata and found it expedient to describe two 

 new genera, 2 I went into a careful study of the penis in these 

 and related genera, which convinced me that the penis had 

 characters worth studying and made me desirous of carrying 

 the study further. This opportunity came in the Fall of 1915, 

 when I had the privilege of spending several weeks studying 

 with Mr. E. B. Williamson in his private collection and 

 laboratory at Bluffton, Indiana. At this time T drew two 



'Notes on The Life History and Ecology of the Dra^onflies (Odon- 

 ata) of Washington and Oregon, C. H. Kennedy. Proc. U. S. Nat. 

 Mus., Vol. 49, pp. 259-345, 1915. 



2 Notes on The Life History and Ecology of The Dragonflies 

 (Odonata) of Central California and Nevada. (In press.) 



