Insects. 9375 
[There is something as unusual as it is praiseworthy in the manner 
in which Mr. Bowles has worked out this interesting subject: I lay no 
stress whatever on the theory suggested for the introduction of the 
species; nor do I regard, as worth much consideration, the fears 
expressed as to its increase to any injurious extent, since that has 
never been the case in this country; neither bas its congener, Pieris 
Napi, ever ventured much beyond its natural food-plant, the water 
cress, and has never, to my knowledge, touched any of our cabbages. 
The interest attached to this paper is of a purely scientific character : 
we see an immense region in which the species is unknown; we see 
the species accidentally introduced, at first appearing sparingly, then 
increasing gradually, then rapidly, and eventually becoming so abun- 
dant as to excite fears for the crops. This, of course, suggests the 
idea of other introductions. That a species should have two or more 
centres from whence it originally diffused itself is highly improbable, 
unless it were assisted by some human agency. We have several 
species which present this prima facie improbability; for instance, 
Vanessa Antiopa, V. Atalanta, Cynthia Cardui, Bombylius medius, 
B. minor, Allantus ater, Bombus Sylvarum, B. terrestris, &c., and the 
carefully elaborated history of Pieris Rapz (now before us) certainly 
suggests the idea that all these may be also colonists, although colonists 
of an earlier date: the subject is one which requires and deserves the 
most careful investigation. It is a well-known fact that some plants, 
as well as insects, are cosmopolitan, and as the former are certainly in 
course of introduction into new localities, it is by no means improbable 
that insects accompany or follow their introduction. If this be so, we 
have as feasible an explanation of the presence of Pieris Rape and 
Vanessa Antiopa in Canada as of our commonest weeds in New Zea- 
land and at Adelaide. 
A second question of no less interest arises out of the first. Does 
any perceptible difference exist between the European and Canadian 
individuals? and if so, does the difference increase or diminish? The 
‘bearing of these questions is obvious; if a difference is originated and 
continued when a European species establishes itself in America, or 
an American species in Europe, and becomes something different from 
its progenitors, we have a first step towards the establishment of a new 
species; the value of the differences will be in accordance with their 
constancy rather than their amount.—Edward Newman.] 
