Insects. 9373 
With respect to the means by which it has been brought into the 
country, some plausible conjectures may be advanced. Of course the in- 
troduction took place during the season of navigation. The turnip, cab- 
bage and other kindred vegetables constitute the principal food-plants 
of the insect; and, adhering to one of these, it must have been carried 
across the ocean, either in the egg, larva or chrysalis ; the last being the 
most unlikely, as the larva always forsakes its food-plant, and becomes 
a pupa in some sheltered situation, usually under the coping of a 
wall, &c. The eggs are laid on the under side of cabbage and turnip 
leaves, where the larva, on emerging, find themselves in close proximity 
to their food. Perhaps the vegetable refuse thrown from one of our 
ocean steamers on her arrival has contained a few eggs or larvae, 
which, under these unfavourable circumstances, have retained their 
vitality ; and from those have sprung the imagines destined to become 
the parents of the species in Canada. The habitat of the insect is 
sull very limited. After making inquiry, I do not think it has ex- 
tended more than forty miles from Quebec as a centre, so that a circle 
of eighty miles diameter would include the present habitat. This may 
seem great progress during the short period of its naturalization, but, 
considering the fecundity and habits of the species, it is not surprising. 
There is some importance connected with the introduction of this 
butterfly, apart from the scientific interest of the subject to entomolo- 
gists. Hitherto Lower Canada has possessed but one species of the 
genus Pieris (P. oleracea, Harris, Pontia casta, Kirby), and this spe- 
cies so insignificant in numbers, at least in the Quebec region, that its 
depredations have passed unnoticed. The new importation, however, 
must be regarded in a different light. As the insect is now per- 
manently settled in the country, is very prolific, and the larve 
extremely voracious, we may anticipate its becoming a great pest to 
farmers and gardeners, not only where it is now found, but ultimately 
in the whole of Canada and parts of the United States. And that it 
will, in the course of time, spread over these regions admits of no doubt. 
The food-plants of the species are cultivated in every part of the 
country, and besides the insect has the power of accommodating itself 
to altered circumstances. Mr. Curtis, in the work before mentioned, 
states that the caterpillars have been found feeding on the willow, and 
on migniouette, nasturtiums, &c. It is, therefore, probable that its 
progress westward will not be impeded by the scarcity of its favourite 
food in certain localities, but that it will overcome all difficulties of 
this nature by resorting to other plants, not confining itself to the 
Crucifere. 
