34 



THE IMAGO 



[CH. 



The diversity of form in these appendages is immense. Except 

 in the Libellulinae, and a few Gomphinae, practically every species 

 is at once determinable by the form of its appendages. Hence 

 hybridization is a very rare occurrence in the Odonata. In the 



Fig. 14. Anal appendages of male Dragonflies. A-H Anisoptera, J-L Zygoptera. 

 A. Austropetalia patricia Tillyard, dorsal view. B. The same, lateral view, 

 c. Gynacantha rosenberghi Selys, dorsal view. D. Gomphus vulgatissimus 

 Linn., dorsal view. E. Bifid inferior appendage of same (hidden beneath 

 8 in D). F. Austrogomphus melaleucae Tillyard, dorsal view, shewing hooks (h). 

 o. The same, lateral view. H. The same, occiput of $ shewing tubercles (t) 

 which engage the appendages of the male. j. Isosticta simplex Martin, dorsal 

 view. K. Ischnura heterosticta Burm., dorsal view. L. Hemiphlebia mirabilis 

 Selys, dorsal view, shewing white ribbon-like inferior appendages, i inferior; 

 * superior appendages. (A, B. D-H x 8, ox 5, J-L x 15.) Original. 



case of those groups where the appendages are sufficiently similar 

 to admit of the possibility, we find very dissimilar developments 

 of the accessory genitalia of segment 2 in the male. Here, then, 

 a second almost insuperable barrier is set up. 



