326 ENTOMOLOGICAL NEWS. [ July, 16 
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 
°On Jan. 1, 1916, Dr. Needham received a copy of Dr. Erich 
Schmidt’s interesting paper on this same subject of penes (Vergleich- 
ende Morphologie des 2. und 3. Abdominal-segments bei mannlichen 
Libellen. Zool. Jahrbuchern. Bd. 39, Heft, 1, 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. 
