1867] 253 
female ; but I think it can be proved, from a scrips of specimens of these forms, 
that, as they approach each other in colour, markings, size, and shape, wo imper- 
ceptibly lose the types of each as they merge into one another, and this, to my 
mind, demonstrates their specific identity to a certainty ; especially when taken in 
conjunction with the fact that they are bred from larvae presenting no perceptible 
points of difference. Further on, Mr. Greene says, " Surely there are dozens of 
species, allowed to be such, more closely resembling each other than cerago and its 
variety." I take the last two words in this sentence to imply that Mr. Greene has 
only seen the lemon-coloured variety pure and simple ; and I therefore ask per- 
mission to say that in my cabinet is a good series of this species, all the 
specimens of which have been bred from larvae collected from various species of 
sallows and willows. Larvae on Salix caprea and S. aurita almost always produced the 
typical X. cerago, while those fed upon the catkins and leaves of 8. viminalis often 
produced the lemon-coloured variety and its variations. Such is my experience in 
breeding this species, which, it will be perceived, is at variance with Mi-. Greene's 
statement that (with him") the larvae producing the latter feed exclusively on 
sallow. 
When I say that there are in my collection about 10 of the lemon-coloured 
variety and its variations, and about 20 of the typical X. cerago and its variations, 
from deep-banded rich brown-ochreous to faint indistinctly marked specimens, 
approaching each other, as I said before, so closely that there is no telling " which 
from t'other," I think it may be fairly assumed that we have only one species 
before us. If there be still a doubt about this, I would add that the dark stigma 
always appears in both forms, as also does the cilial brownish colour on the fore- 
wings ; and, though the outer row of minute spots is sometimes obsolete in the 
paler forms, my very lightest specimen has this character well defined ; whilst in 
two larger specimens, below it, these spots cannot be seen at all. 
Again, some other species of this genus vary very much in colour, particularly 
X. aurago and X. gilvago, of which latter Mr. Greene himself gave me, last year, tho 
darkest pair I ever saw. 
My remarks that different kinds of food affect the future imago might open a 
question which I will not now go into ; but that it does so I am quite able to show 
in more instances than one. — C. S. Gregson, Stanley, neax Liverpool, March 
\st, 1867. 
Notes on variation, Sfc, in Lepidoptera. — I have read with much pleasure and 
interest the remarks of my friend Dr. Knaggs, in reply to my notes in the March 
No. of the E. M. M., upon the supposed causes of variation in colour, form, size, 
&c., in certain Lepidoptera. I think I now understand his position, as to E.Ulustraria, 
but I am not sure. Unfortunately, I have never had an opportunity of breeding 
this insect myself, and, therefoi'e, I only know its habits from hearsay, or from 
what I have read of the experience of others. Will Dr. K. or some other competent 
person kindly answer the following questions : — 1st. Am I correct in supposing 
that eggs laid by illustra/ria in the spring produce in summer delunaria, and that 
eggs laid by this latter produce, next spring, illustraria, and so on ? 2nd. Do ALL 
the pupae fi-om the spring-laid eggs emerge in summer, and if so, are all delunaria ? 
