BY R. J. TILLYARD. 



187 



Aj does not at any point reach Ciio or fuse witli it. Hence no 



anal loop comparable to that in the J'Jschnincf. or Lihelhdidff can 



be formed. In this connection, it is to be hoped that the anal 



tracheation of such forms as //aiye?*^**' (Fig. 19) will l)e worked 



out by those who have access to them. The small loop there 



formed may quite probably be enclosed between Aj.o as the upper 



part of its basal side, Aj as the lower part of its l)asal side, Cuo as 



the upper part of its distal side, 



and the small branch-trachea 



from Cu2 (shown in A. hetei^o- 



clit.ns) completing its distal side 



lower down and joining Aj. In 



that case, the correct notation 



for the wing-veins will be that 



given in Fig.l9. The "anal 



loop" of Hagenius, under these 



circumstances, is not homologous, 



in any sense, with the anal loops 



of the other groups, but is niore^'g-'^--^«-^«'»"^^^^^'^'^^^^^^^''S^^>'«'^^ 



» ,1 , p 1, • 1 Portion of imasinal hindwing-vena- 



ot the nature or a subtriangle. 



Fig. 19. 



tion, with suggested notation for 

 the descending branches of the anal 

 vein (not yet confirmed by analysis 

 of nymphal wing). From a speci- 

 men sent by K. B. Williamson, 

 Bluffton, Indiana, U.S.A. 



The point cannot, however, be 

 settled without a study of the 

 larval wing-tracheation. 



If my interpretation of the 

 branchings of A in the Gomphinoi 

 be correct, Needham's notation for that subfamily will need 

 altering. In his figure for Gomphus descriptus (Joe. cit., p. 708), 

 A;j and Ao remain as indicated, but the vein labelled Aj must be 

 altered to Cug,, ( = proximal branching of Cu.,). His figure on 

 p. 7 07 also shows that this is so. Probably A^ forms the greater 

 part of the weak zigzag vein descending between Ao and Cuo,„ 

 and arising from A 2 one cell below the subtriangle. 



It is very necessary that other genera of Gomphina' should be 

 studied in this manner. A satisfactory classification of this sub- 

 family has not yet been attained, but a study of the larval wing- 

 tracheation would go far towards establishing it, and would, in 

 any case, reveal any hidden convergences which may be lurking 



