326 ENTOMOLOGICAL NEWS. [ July, 'l6 



views each of the penis in over three hundred species of Zy- 

 goptera. Since my arrival at Cornell I have had the privilege 

 of spending altogether two weeks studying the species of Zy- 

 goptera in the collections of the Academy of Natural Sciences 

 of Philadelphia, and of Dr. P. P. Calvert through his courtesy. 

 To date I have drawn the penes of over five hundred species 

 of Zygoptera, having made altogether over one thousand 

 figures, and am hoping to continue the work until the subject 

 is completed, as a monograph.' 



I wish here to thank Mr. Williamson and Dr. Calvert and 

 Dr. Skinner of the Philadelphia Academy, who have so gen- 

 erously opened their collections to me, as it is only through 

 such interest and generous assistance that this study has been 

 made possible. 



When this work was begun, I felt some assurance that the 

 penis would be, not only a good generic, but also a good 

 specific character. More extended study however has shown 

 that only a monographic study of the penes in the entire 

 group of Zygoptera will reveal just how far these organs can 

 be trusted to show true relationships between species and 

 groups, for it has already become evident that the value is 

 very different in different groups. 



The accompanying text figure is a diagram showing what 

 seems to me to be the zygopterous penis stripped of its special 

 modifications, in other words what might be its most general- 

 ized form. I have no evidence that this is also its most primi- 

 tive form, as in those genera usually considered most primi- 

 tive the penis may be most fantastic in the complex modifica- 

 tions of these simple parts, so that it appears that there has 

 been a" tendency to a reduction in its complexity from the 

 more primitive forms to those more recent. However there 

 are undoubted exceptions to this. The zygopterous penis 



3 On Jan. i, 1916, Dr. Needham received a copy of Dr. Erich 

 Schmidt's interesting paper on this same subject of penes (Vergleich- 

 ende "Morphologic des 2. und 3. Abdominal-segments bei mannlichen 

 Libellen. Zool. Jahrbiichern. Bd. 39, Heft, I, 1915.) It was the first 

 intimation I had had that some one else was working on the same 

 subject. Dr. Schmidt has dealt with seventy species of Zygoptera. 



