II] 



EXTERNAL FEATURES AND SKELETON 



35 



As hundreds of figures of the appendages are available in 

 systematic works, we have contented ourselves with figuring a 

 few types in fig. 14 (see also figs. 170, 174, 178). As regards the 

 superior appendages, the narrow leaf-like form is perhaps the most 

 primitive, and remains extant in most females still 1 . An expansion 

 of this gave rise to the broad Petalura-ioim, while various simple 

 modifications led in the opposite direction to the form seen in 

 Aeschna (fig. 170). Developments of a forcipate nature are very 

 frequent. In the Libellulinae a slightly reduced pointed type 

 obtains almost throughout, and may 



be conceived of as lying somewhere 



/ V 

 between the lanceolate and strongly <^^> l 



forcipate types. The much reduced 

 divergent appendages of the Gomphinae 

 (fig. 14 D-G) appear to be the most 

 highly specialized of all. 



In the case of the inferior ap- 

 pendage (fig. 15) the primitive type 

 was certainly correlated with a wide 

 occiput, and hence may be conceived 

 of as not very far removed from 

 the form found in Petalura (a, 6j). 

 A simple change in this form (by 

 median cleavage) leads us directly to 

 the Gomphine type (c ls d^). With the 

 increase in the size of the eyes and the 

 decrease in the size of the occiput in 

 Aeschninae and Libellulidae, the append- 

 ages tended to lengthen, the inferior 

 becoming sub -triangular and curved, so 

 as to fit over the occipital tubercle (6 2 , 

 c 2 , d 2 ). The form in Petaliini (c 2 f ) per- 

 haps preserves for us the ancient trun- 

 cated form, while developing a larger 

 median process to reach forward to the 

 point of union of the eyes. 



Fig. 15. Assumed phylogenetic 

 series of inferior appendages 

 in male Anisoptera. a Peta- 

 lura ingentissima Tillyard. 

 &! P. gigantea Leach. Cj Gom- 

 phus vulgatissimus Linn. 

 d l Austrogomphus melaleucae 

 Tillyard. b 2 , c z , d 2 , three 

 forms commonly found in 

 Aeschninae and Libellulidae. 

 c ? ' Austropetalia patricia Till- 

 yard. The series are (i) a, 

 6j, c x , d 1 ; (ii) a, b 2 , c 2 , d 2 ; 

 (hi) a, b 2 , c z- Original. 



1 Dimorphic appendages occur in the Palaearctic Boyeria irene, some females 

 having them long and some short. 



32 



