31 
PAPERS READ BEFORE THE SOCIETY. 
VARIATION IN SCIADION (GNOPHOS) OBSCURATA. 
(Read January “20th, 1903, by Louis B. PROUT.) 
I know of no species in the whole of our lepidopterous fauna 
which possesses greater interest for the student of variation than the 
one which I have chosen as the subject of my paper this evening. In 
the eyes of the fancier of mere freaks and sports, indeed, it would 
certainly take a back seat compared with Arctia caia, Spilote grossu- 
lariata, and many others that could be mentioned; and with the 
possible exceptions of the very localised red-sandstone form (var. et ab. 
argillaceana, Stgr.), and the most extreme white Lewes aberration, I 
have never seen a specimen—so far as I can recollect—which would 
have fetched more than a few pence at Stevens’.* 
No, its interest, as I hardly need to remind you, lies in the fact of 
its beautiful and easily-comprehended adjustments to its very varied 
geological environments,! and its consequent usefulness as an illus¬ 
tration of the truth of the now almost universally accepted theory of 
Natural Selection. As Mr. Tutt wrote, in his articles on “ Melanism 
and Melanochroism ” (Ent. Bee., i., p. 123) :— 
“ But to take a special case where the direct influence of humidity 
can, compared with ‘ natural selection,’ have very little to do with 
the variation in colour. Gnophos abscurata, as is well-known, is one 
of the most striking examples. I devote a drawer to the series of this 
species in my collection, and what do I find ? I find that among the 
specimens captured on the chalk a large percentage of pale forms 
occur, assimilating most perfectly to the chalk on which they rest; 
but even here, in the more exposed situations, there is general varia¬ 
tion within narrow limits in both sexes, and the females are generally 
darker than the males. I have always supposed this latter phase to 
arise from the fact that the females appear to rest more among the 
herbage than do the males. On very impure limestones grey forms 
occur, assimilating most perfectly with the limestone ; while on peat, 
dark peaty-black coloured specimens are found. On slate formations 
intensely dark slate-coloured, or black specimens are the ordinary 
form, while I have very red specimens from the red sandstone forma¬ 
tion. Here is a complete response to environment, and I leave my 
readers to infer how special races of this species have been brought 
* Mr. Barrett (Lep. Brit., vii., p. 160) mentions one casual aberration from 
Bond’s collection, of wholly shining greyish white, with scarcely a trace of dark 
scales or markings. 
f Vaughan is reported to have once exhibited at the Entom. Society a 
very varied series in illustration of this, but unfortunately the details are not 
recorded. 
