70 



may be useful to refer to the more prominent differential characters, 

 they have been tabulated as follows : 



1. The fore-wings are broader in proportion to their length in 

 unidentaria than mfermgata, and the outer margin is more rounded 

 in the former. 



2. The central fascia is always black in zinidentaria, but, although 

 sometimes very dark, is never black mferrugata. 



3. The band following the central fascia is ochreous-brown inter- 

 sected by a wavy ferruginous brown line in miidentaria ; whilst in 

 Jerrugata this band is whitish or greyish, and is intersected by a 



blackish wavy line. 



4. The outer edge of the band following central fascia is never 

 well defined in unidentaria^ but generally is so in ferrugafa, 



5. The outer marginal area of fore-wings is less ornamented in 

 unidentaria than in ferrugata. 



6. The outer marginal area of hind-wings is never so conspicuously 

 bordered with darker in unidentaria as it is in ferrugata. 



The above points of difference between the two species should 

 amply suffice to separate imidentaria ixom ferrugata. It may, how- 

 ever, be mentioned that the " twin spots " situated just above the 

 middle of the sub-marginal line are generally rather smaller in uni- 

 dentaria than in ferrugata ; but no reliance can be placed on this 

 character in itself. In a general way unidentaria is distinguished at 

 once by the black fascia of fore-wings ; the only specimen of ferru- 

 gata that I have seen which could possibly be confounded with 

 unidentaria is the one marked C in the box of mixed forms ex- 

 hibited. 



Returning to the two series of ferrugata, we find that two very 

 distinct forms are represented, and we also find that the individuals 

 in each series agree one with the other in colour and marking. To 

 these facts we have to add a still more important one, and that is 

 that the specimens in each series agree almost exactly in colour and 

 ornamentation with their female parent. Now, from experiments with 

 other species of moths, I have always found that where the male 

 parent was known as well as the female, and the sexes were repre- 

 sentatives of different forms of the species, the progeny would com- 

 prise specimens coloured like the male, as well as those of the 

 female coloration. In these series oi ferrugata, however, the speci- 

 mens are uniform in each, and there is no evidence of any one 

 individual of one series showing a tendencv to vary in ths direction 

 of the specimens of the other series. This fact appears to me to be 

 remarkable, and I can only suppose that in each of these cases the 

 male parent must have been of the same form as the female parent. 



Consideration of the facts adverted to, together with the know- 

 ledge that in the larval stage the species are very difficult to distin- 

 guish, leads me to the conclusion that although we are probably 

 correct in keeping unidentaria specifically distinct from ferrugata, 



