710 ON THE GENUS PETULARA, 



4. A p p e n d a g e s : in these we have tlie most remarkablf^ 

 divergence of all. The appendages of Petalura (male) cannot be 

 brought into line with those of other Odonata at all. It resembles 

 the Libellulidce and ^Eschnince in having only one inferior 

 appendage; both the Goinphinm and Caloiyterygidce have two. 

 Moreover it would require a stretch of the imagination to see in 

 the breadth of its single appendage an approach to bifurcation, 

 though it is possible that the double inferior appendages of the 

 GomphincE may have been brought about by that means. As 

 regards the superior appendages, they are beyond all doubt most 

 remarkable, and would almost appear to have been developed for 

 use as a rudder during flight. The insect is able to open and 

 shut them, and when flying holds them fairly vertical, but I have 

 not been able to observe what use is made of them when the 

 insect is about to descend, or when it is hovering in the air. 

 Here again imagination may depict the process of forcipation, as 

 we see it in the Calopterygidce^ being brought about by the 

 change, firstly, to a laminate appendage, as in Petalura, and, 

 secondly, by the hardening of the upper and stronger curved edge 

 of the lamina, and the gradual loss of the under portion. In this 

 case we mio-ht also regard the teeth that occur often on the 

 undersides of forcipate appendages as the relics of the lower 

 portion of the lamina. A careful study of a number of forcipate 

 forms may reveal the truth of this supposition, but at present it 

 cannot be pressed. The appendages of the female are not 

 remarkable, and do not call for comment. 



5. W i n g s : these show no connection whatever with the 

 Calopterygidce, but a considerable resemblance to the Gomphince. 

 Fore- and hindwings dissimilar. (a) Pterostigma of enormous 

 length; narrow as in the ^schnince, and not convex as in the 

 Gomphince,. Here, however, the genus Ictinus is again an excep- 

 tion, as it shows a considerable lengthening and narrowing of 

 the stigma, (b) Wing -triangles distinctly dissimilar, that of the 

 forewing being narrower than that of the hindwing, as in the 

 Libellididce. However, an examination of the simple triangles of 



