10 MR. R. J. TILLYARD : LIFE-HISTORIES AND 



like those of Anew, or whether they show a tendency to form the overlapping 

 tile-like folds of Libellulidse. Unfortunately^ the living larvse are most 

 difficult to obtain. 



Hortense Butler *^ has proved the existence of two setse on the lateral lobe 

 of the labium in very young Anax nymphs^ but these very soon disappear. 

 This might be regarded as proof that the nymphs of jEschnince originally 

 possessed setse, which later on disappeared, being only retained in Gyna- 

 caiitha and as a disappearing remnant in A)iax. I prefer, however, to see 

 in the phenomenon shown by the young AncicV nj-mph an attempt to develop 

 setse ca3nogenetically. They may be of use to the very young larvse, and 

 still may not yet have reached their full cpenogenetic development. This 

 view would demand the recognition of the Gijnacantha larva as the most 

 csenoo-enetic of ^schnine larvee, with the larva of Anax intermediate in 

 position between it and the larva of ^Esdina. Neither the archaic Petaliini, 

 nor any of the Gomp/ii)ia', so far as I know, have sette in the nymphal 

 labium — a strong point in favour of the csenogenetic development of these 

 structures in Gynacantlia. 



To the yEschnince as usually constituted, I also add, as an archaic remnant 

 of undoubted jEschnine origin, the isolated Petalia-gromp of genera. These 

 mioht well be claimed as of co-ordinate rank to the whole of the rest of the 

 JEsclinimi'. I have, however, considered it sufficient to allot to them the rank 

 of a " tribe ^' within the subfamily, so that we now have three very distinctly 

 marked tribes, which may be named after their most prominent genera, and 

 defined as follows : — 



Tribe I. Petaliini. 



M2 distinctly arched upwards near the beginning of the pterostigma, but 

 not approaching Mi as closely as in other ^^schnince. Triangles rather shorty 

 usually only two-celled. Rs unforked. Rspl present. Mspl absent. 

 Oblique vein far distal from subnodus. Wings with a set of remarkable 

 semitransparent brown or ruby-red spots along costal border. Eyes touching 

 only for a short distance. Inferior anal appendage of male trifid. Ovipositor 

 of female of typical ^Eschnine form. 



Larva with broad flattened abdomen carrying fin-like lateral segmental 

 projections (strongly suggestive of Trilobite ancestry). Dorsal tubercles 

 present. Labium with typically iEschnine mentum and lateral lobes ; outer 

 apical anoie narrow, rounded ; inner border finely crenulate. Appendages 

 short, segment 10 small and half enclosed in a hollow of 9. 



Includes the- genera Petalia, Hijpopetalia, PhyUopetalia, and Austro- 

 petalia, n. g. 



* "The LaLium of tlie Odouat.i;' Tran^. Amer. Ent Soc. xxx. (1904) pn 111-134 



