234 STUDIES IN AUSTRALIAN NEUROPTERA, iii., 



Bi = S-, Bn^Sg, B, = 89, and B4— -Sk,. It will be seen at once 

 that the Banksian Line formed by the middle longitudinal por- 

 tion of these four sectors is the distal portioti of the pseiidu 

 media. 



The importance of these four Banksian sectors does not, how- 

 ever, end here. Three of them, viz., B., to B4, after dropping 

 below the level of the pseudo-media, again become bent longi- 

 tudinally to form a second Banksian Line. This is clearlv seen 

 to 1)6 the distal portion of the pseiido-cubit^is. 



(2) The true Media (M). —In the tracheation, the stem of M is 

 distinct from R; in the venation, the two are fused basally for a 

 short distance. The true media then divei-ges slightly from R, 

 and runs to a point called the median fork (mf), lying imme 

 diately below the radial fork in the hindwing, but a little 

 proximad to it in the forewing. From here onwards, the course 

 of M in the venation is so disguised that it is necessary to turn 

 to the tracheation for elucidation. Then we see at once that M 

 has two branches, Mj and M.,, arising at 7uf — a fact which could 

 never have been proved from the imaginal venation alone. The 

 problem is also complicated by the very different behaviour of 

 these two branches in fore and hindwing respectively; so that it 

 will be necessary to trace them out in each wing separately. 



In the forewing, Mj on leaving m/ arches slightly upward, but 

 does not come into contact with Rs, from which it remains 

 separated by a full cell's width. It then runs longitudinally 

 towards the down-curving portion of B4, and passes close under 

 the sector for a short distance, before it (MJ turns downwards 

 in a second bend. It then turns to run longitudinally again for 

 a second short distance, and again approaches and runs alongside 

 B4 Finally, it breaks up into two small branches descending 

 to the wing-border. Thus we see that M, performs the part of 

 another Banksian sector, and helps in turn to form both the 

 pseudo-media and the pseudo-cubitus. 



The lower branch, Mo, on leaving m/, runs concavely to Mj, 

 and then approaches it again, so as to isolate between Mj and 

 itself a small oval area, which can be recognised at once in the 

 imaginal venation as the cell lying just above the "divisory 



