26 
UNDER SIDE 
K.—An apical dark cloud is 
sometimes present on fore¬ 
wing, but no cloud or shade 
on hind-wing. 
K.—A dark apical cloud is al¬ 
ways present on fore-wing, 
and a distinct grey cloud 
is conspicuous at the outer 
margin of hind-wing. 
GENERAL OBSERVATIONS. 
Except that unidentaria is slightly the larger insect, I see no 
structural differences except in the genitalia as already recorded. All the 
markings are jirone to considerable variation, especially the size and 
shape of the median band, which is often bisected by a broad paler 
shade. The best character for distinction appears to be the dark shade 
on the hind wing, as it seems pretty constant both on the upper and 
under sides (H. and K.).” 
I have very little to add to this ; 1 would remark that the median 
band of fer rug aria, Haw., is never black, though sometimes very dull 
brownish or greyish-red; that a stronger point might perhaps be made 
of the paler outer area of the fore wings in unidentaria ; that the fringes 
of ferrugaria are much more distinctly spotted than those of unidentaria ; 
that the contour of the outer margin of the central fascia, and of the 
corresponding line on the hind wings, though very prone to vary, is 
nearly always distinguishable in the two species; ferrugaria seeming 
never to be so deeply bent inwards below the middle, or the band so 
attenuated on the inner margin, as is general in unidentaria; and that 
the dark mark on the underside of unidentaria , near the base of the costa, 
generally so conspicuous, is either weak or wanting in ferrugaria. 
Superficially also, the whole tone of the colouring of the two species 
is generally different; it is very difficult, though not impossible, to pick 
out a specimen of each really agreeing in the colour of the band; and 
the Continental authors are probably right in considering that in 
unidentaria the band is never so distinctly traversed with dark lines as 
in ferrugaria; though, unfortunately, some of our British forms of the 
latter are almost as absolutely devoid of lines as it would be possible to 
imagine; but it is tolerably certain that no form of unidentaria corres¬ 
ponds at all to the extreme striated forms of ferrugaria, indicated by 
Staudinger as ab. spadicearia (“ fascia media in strigis dissoluta *’) or by 
Haworth as salicaria (“ obsolete strigatse, nec fasciatie ”). 
Variation. —Both species are extremely variable, and it would not 
be difficult to occupy a whole paper with studies of their variation. A 
few general observations under this head seem worthy of being first 
brought into jirominence :— 
1. —As is usual in closely-allied species, the variation is largely on 
parallel lines. 
2. —The variation of ferrugaria, Haw., is largely geographical; that 
of unidentaria, much less so. 
3. —On the other hand, the influence of heredity, exceedingly strong 
in both species, is shown even more strongly in unidentaria ; so that 
while the red and black forms exist together in most localities, yet the 
black forms hardly ever throw red in their progeny. The exceptions 
are so rare that those which have come under my notice can be 
recounted in a very few words. Mr. W. H. B. Fletcher’s experience 
