RJ.Z 



322 MONOGRAPH OF THE GENUS SYNTHEMIS, 



singled out at all. I figure it simply to show to what extraor- 

 dinary lengths variation may go in this unstable genus. 



To sum up, I think the following conclusions may be fairly 

 deduced from the study of Synthemis wing-venation : — 



Synthemis is an archaic furm, eoolving along Macromian lines 

 (as regards venation). Variation and "freaking" are rampant 

 in the group, shewing that the final and most advantageous form 

 of wing has not yet been attained. The most advanced wing- 

 type in the genus is probably that of S. clavicidata, with its 



braced pterostigma and scarcity 

 of cross-veins. S. cyanitincta 

 shews a strong tendenc}^ to as- 

 sume the truly Corduline pro- 

 perty of a recessed triangle in 

 the hindwing. The oldest forms 

 are probably those with abun- 

 dant cross-veins, such as S. 

 Fig.l—Vf'mgsoi Syntkemh claviculata(x2). inir'anda, S. regina, and S. 

 onacrostigmix. In these, there is a more primitive condition of the 

 anal loop, which has not yet become consolidated into a single 

 compact Macromian loop. These are also three of the largest 

 insects in the genus, though by no means the best fliers. The 

 tendency is towards a reduction in size, as well as a reduction in 

 oross-veins. (I am inclined to regard .S'. olivei as an advanced 

 member of the genus, with traces of csenogenesis in the anal 

 loop). 



Synthemis is essentially different from Macromia in that, 

 though following on similar lines of development, it is in a far 

 less complete and specialised stage. 



In his new work on the Libelhdince, Dr. Ris has divided that 

 subfamily into groups having gi-eat phylogenetic value. He 

 places at the beginning of each group the most archaic genus still 

 extant, which contains the essential characteristic of that group, 

 and leads up to the most highly specialised genus in the same 

 group. The result is a series of groups containing widely diff'erent 

 forms, but giving a classification undoubtedly of more educational 



