THE GENUS ENNOMOS (SENS. STR.). 27 
plants Sisyrinchium bermudiana, S. californicum, and Spiranthes 
romanzofiana in Ireland, not to mention certain fresh-water 
sponges, crustacea, and other forms. 
As a further proof of the antiquity of H. quercinaria in 
Kurope, its British distribution can be adduced. Its range 
is mainly English, as (except for a very dubious Lanark record) 
it only reaches Yorkshire, but, what is very significant, it 
reaches Ireland. From this it is clear that it is one of the 
forms which entered England from the south and succeeded in 
reaching Ireland by means of the South Wales land connection 
—a connection that broke long before Ireland became an island, 
for the iron barrier joining up Scotland aud Ireland via Islay 
and Donegal existed for a very much longer period than the 
other passage, as one can prove, independently of geological 
considerations, by considering such facts as the presence of 
the Arctic hare and the absence of the common English 
species in Ireland. All of these facts prove that, even at that 
remote period, EH. quercinaria had a southern distribution in 
Europe, and this fact in turn thrusts back the origin of the 
species in our continent to a very remote epoch indeed. No 
matter what theory we adopt about the origin of the two species, 
it is certain that the American subsignaria is nearer the original 
stock, as is apparent from its colour, wing-shape, larva, etc., but 
the change in quercinaria is not great, simply displaying itself 
jn minor and less important details. 
Lire History oF THE Two Forms. 
The biology of the two species in question is very similar 
(although perfectly distinct in all their stages). Subsignaria 
lays its eggs in the same semi-imbricated fashion as quercinaria 
on the bark of trees, but they are less barrel-shaped, flatter, and 
a little browner. 
The larve, too, bear a general resemblance to each other, 
but those of the Canadian insect are, on close examination, 
found to be less specialised, for they are smooth and less rugged, 
and, whilst they possess some of the characteristic humps of 
quercinaria on the last abdominal segments, those found on the 
anterior parts of quercinaria larve are not represented. Further, 
in colour the larva is a deep black, with a rich brown head, thus 
contrasting greatly with the clay-coloured quercinaria larva. 
The pupe of the two species are very close, as one might 
expect, and are spun up in leaves in both cases. The pup» 
of subsignaria are a little deader in tone and more stone-like in 
colour. 
The imago of E. subsignaria is a particularly featureless 
creature, being, with the exception of the yeilow-brown discoidal 
spots (only shown below), of a uniform glistening, snowy white. 
