BY H. J. TILLY-ARD. 235 



veinlet"— the latter, of course, being a portion of M^ itself. 

 After running close below Mj for a short distance, M„ drops 

 down to the level of the pseudo-cubitus, and plays a part, in 

 helping to form that vein, exactly similar to the part played by 

 Ml. Finally, it branches into two, and drops to the wing- 

 border. 



It will be seen that, owing to the fact that M, and Mg in the 

 forewing twice recede from and approach towards one another, 

 two curved areas are isolated off between them. In the imaginal 

 venation, owing to the fusion of Mj with Mg for about half a 

 cell's-length along the pseudo-media, these two cells are widely 

 separated. The first is the small cell above the "divisory 

 veinlet " ; the second is the large hexagonal cell lying next distad 

 from the so-called third cubital-cell of Banks (cti^ in Text- fig. 4). 

 These two cells being enclosed by both branches of the true 

 media, I propose to name them the Jii'st and second intra-median 

 cells respectively, with the notation im^, im,, so as to distinguish 

 them clearly from the three median cells, ni^, m^, and m^, which 

 are of course the "cubital-cells" of Banks. As regards the 

 term "divisory veinlet," this is obviously a most misleading and 

 inaccurate term, since it is, firstly, not a veinlet at all, but a 

 portion of the main vein Mg, and, secondly, it does not divide 

 anything, since the true third median cell ("thii'd cubital" of 

 Banks) lies entirely outside it. I propose, therefore, to term 

 this small portion of M„ the median loop, with the notation m.1. 

 It should not be lost sight of, also, that the upper part of the 

 cross- vein from which rtil appears to arise is also a portion of Mo, 

 and is therefore analogous with the upper part of the well-known 

 formation in the Dragonfly wing, called the arculus. It is not 

 homologous with it, however, since in the Dragonfly wing it is 

 the main stem of M which drops from R to form the arculus, 

 whereas in the present case it is Mj dropping from M at mf. 

 Th§ term rnedvin arculus (ma) is suggested as a suitable name 

 for this formation. 



In the hindwing, the behaviour of the true media is different. 

 The main stem M is very short, so that the median fork mf 

 comes directly under the radial fork rj\ not far from the base of 



