IBY R. J. TILLYARb. 



305 



number, all quite separate, but closely set together, as shown in 

 the figure. 



The ret'inaciihim^ or catch, whicli holds these bristles in place, 

 is a very generalised structure, being nothing more than the 

 somewhat stittened haii's or scales which arise from the underside 

 of the cubital vein of the fore wing, and run oblique!}^ forward 

 and distad. The manner in which the fi'enulum is held in place 

 by these hairs is closely similar to that by which the jugum of 

 Pirhis is held in its groove by the hairs on the costa of the 

 hindwinu'. 



Text-fig. 14. 

 Wing-coupling apparatus of Plusia rerticillata (Guer.), ? , showing fren- 

 ulum of two strong bristles, and retinaculum of stiff hairs arising from 

 cubitus [Cii); viewed from beneath; ( x30h hi, humeral lobe. 



In the Noctuid genus Flusia, in which males and females fly 

 almost equally well, we may see a much more liighl}' specialised 

 coupling-ap[iaratus in the female. Here, the frenulum is com- 

 posed of only two (sometimes three) bristles, apparently formed 

 by the fusion of an original greater number, and almost as long 

 as those af the male. The retinaculum, too, is more strongly de- 

 veloped, the hairs being stiffer and more closely set, so as to form 

 a very definite catch for the frenulum (Text-fig. 14). 



Turning next to the males, we find, in every case, a highly 

 specialised condition present (Plate xxx., fig.8, and Text-fig. 15). 

 Here, the frenulum is represented by a single huge bristle, 

 which may even reach to more than half the length of the wing, 

 as in the family Fsychiche. As Packard (10) has already shown, 



