BY K. J. TILLYARD. 



179 



Stage 4.— The final stage in the phylogenetic development of 

 the anal trachea is to be seen in most of the Libellulince and in 

 the Eucordtdiini (see Figs. 11-1 2, and Plate xi., figs. 7-9). Here 

 A.j has outdistanced all the other branches in development, and is 

 to be seen as a very long and strong trachea ruiniing slantwise 

 distad from Ac. As in the ^EschniiuF, it still forms the basal 



Fig. 12. 



Fig. 11. — Hemico7^dulia tauSe]ys, (S . Tracheation of full-grown iiyniphal 

 wings. A, forewiiig ; B, hindwing. (Sydney; Jan., 1914). Note 

 the narrowing of the imaginal wing-border in the forewing. 



Fig. 12. — Hemicordulia tau Selys, S . Basal portion of imaginal venation. 

 (Heathcote, N.S.W.; March, 1907). 



border of the so-called "anal loop," though that term can no 

 longer strictly be applied to the elongated Italian loop now before 

 us, since A^ has ceased to play any part in its formation. Aj, 

 shrivelled up almost beyond recognition, now fails even to reach 

 Cug. But the latter, strongly developed in a slantwise direction, 

 very similarly to Ao, now forms the complete distal border of the 

 loop, and also gives off a branch Cu-.^,, which breaks back to form 



