BY R. J. TILLYAUD. 233 



in Plate xi., figs. 1-2. As a further aid to this study, I have 

 given tlie correct interpretation of the imaginal wing- venation 

 in Plate x., overlaid in red, on transparent paper, by a diagram- 

 matic representation of the pupal tracheation, to show the part 

 played by each trachea in the formation of the veins. We shall 

 divide our study up into three parts, viz., (1) the radial sector 

 and its branches, (2) the true media, and (3) the true cubitus. 

 Having traced these out, we can then visualise the extraordinary 

 structure of the pseudo-media and pseudo-cubitus. 



(1) The Riidial Sector (Rs) and its Branches. — The radial sector 

 (Rs) arises from R, in the forewing, at a considerable distance 

 from the wing-base, at a points called the radial fork {rf). Pupal 

 tracheation and imaginal venation agree on this point. In the 

 hind wing, however, the supposed origin of Rs in the imaginal 

 venation (the point x) is seen by reference to the pupal trachea- 

 tion to be a false origin, and really represents the origin of the 

 first cross-vein between R and Rs. The true origin lies mucli 

 closer to the base, at the point marked rj\ which has up till now 

 been taken as the origin of M. 



In both wings, if we look at the tracheation, Rs gives off ten 

 posterior branches. These J have named Sj, &?2 • • • S}o ^or con- 

 venience of reference (instead of the more cumbrous Rs^^, Rs^, 

 etc.), Sj being the most distally placed. Turning to the imaginal 

 venation, we see that only six branches of Rs are visible, viz.. 

 Si to Sg. What has happened to the other four, viz., S>. to Sjq'? 

 The answer is supplied by a glance at Text-fig.5, followed by a 

 reference to the ti-ansparency overlying Plate x. These four 

 branches are, in fact, bent in their middle portions so as to ruii 

 lonyitudinally, and thus give rise to a continuous Banksian 

 Li7ie, homologous with that already shown to exist in a number 

 of Myrmeleontid genera.* For this reason, I propose to call 

 these four branches the four Banksian sectors, Bj to B^. Thus 



* See No. 1 of the.se Studie.s, in these Proceedings, 1915, pp. 734-752, 

 Vol. xl. , Part 4. Navas has termed this line in Myrmeleontidce the "linea 

 plicata," a singularly inappropriate term, it seems to me, for a formation 

 which, though of composite origin, is in its highest expression an absolutely 

 straight line without any folding in its composition. 



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