32 



THE IMAGO 



[CH. 



Fig. 11. Right auricle of 

 Austropetalia patricia 

 Tillyard, <$ (x 10). 

 Original. 



above, hollowed out beneath, and often denticulated distally. 



Their function is unknown; but it seems 



fairly clear, from their method of occurrence, 



that they must act in conjunction with the 



anal angle of the hind-wing in controlling 



certain phases of flight. Otherwise, it would 



be hard to account for their absence in Anax, 



Hemianax and Hemicordulia, the only genera 



of the Aeschninae and Corduliinae which 



have rounded hind-wings in the male. In 



the Petalurinae, the auricles are peculiar 



and of a primitive form, being merely 



oblique convex swellings in front of a small 



depression. 



The Accessory Genitalia of the Male, situated on the sternites 

 of segments 2-3, are dealt with in chap. xi. The Ovipositor of 

 the Female, developed from the sternites of segments 8-9, is like- 

 wise dealt with there. 



The Anal Appendages (figs. 12-16). As these differ consider- 

 ably in the two suborders, we shall deal with them separately. 



1. Anisoptera. The males have two superior appendages 

 (sup) developed from the posterior end of the tenth tergite. They 

 also have, below and between these, a so-called median inferior 

 appendage (inf) representing the appendix dorsalis of the larva 

 (p. 91). This "inferior" appendage is badly named, since it lies 

 directly above the anus, and is developed from the reduced tergite 

 of the eleventh segment. In the females, the inferior appendage 

 is absent. The superior appendages are, however, present, though 

 apparently functionless. They are usually smaller than in the 

 males, and are called simply the anal appendages, since they are 

 the only ones present. 



The anus itself (a) is surrounded by three small processes or 

 valves, which are the vestiges of an original twelfth segment. Of 

 these, the median dorsal lamina supra-analis (la) represents the 

 reduced tergite, the two latero- ventral laminae sub-anales (la) the 

 reduced bipartite sternite of this lost twelfth segment. A soft 

 paired tubercle below the anus (st n ) represents the vestiges of the 

 similar but larger sternite of the reduced eleventh segment. The 



