BY R. J. TILLYARD. 



621 



Text-Fig. 70. 

 Forewing of an undetermined Tachinid (x 5) immediately after full ex- 

 pansion. Lettering as on p. 535. For full explanation see text. 



glass jar. Text-fig. 70 shows the state of the irnaginal venation 

 in the freshly expanded wing of this fly. Quite a number of 

 veins were strongly indicated, at this stage, which were seen to 

 disappear again not very long afterwards, when the wing be- 

 came hardened up. We may mention the following: — 



(1) What appeared to be an incipient attempt at redevelop- 

 ing R 3 was visible as a very slight band arising from K2 in the 

 position shown, but not reaching the wing border. If this were 

 really R 3) it must indicate an attempt to reproduce a very 

 archaic stage, since the forking of R 2+3 has been lost in all 

 Brachycera, and therefore, presumably, in the ancestors of the 

 Cyclorrhapha. 



(2) M 2 was clearly visible as a distinct band right up to the 

 wing-border. As soon as the wing had hardened up, the only 

 ebitinisation left of this vein was the short stump-vein indi- 

 cated by the continuous black line arising from Mi in Text-figure 

 70. 



(3) The course of M 3+4 was clearly marked as a weak band 

 arising from mf\an<\ running parallel to, and a little above, 

 Cu 1# This vein divided distally into M running up obliquely 

 to meet the cross-vein im, and then bending again to run longi- 

 tudinally to the wing-border, and into M 4j which turns at right- 

 angles t<i M :34 _ 4 as a short transverse vein and joins Cu x imme- 

 diately below its point of origin. Besides these formations, 

 M 3+4 was connected, just distad from mf' , by the cross- vein 

 m-cx, to f'uj. As the wing hardened up, all the main stem of 



