43 
As soon, however, as immense tracts of land are cleared of their natural growth 
and sown with those plants so widely cultivated for man’s sustenance, the 
insects, deprived of their proper food plants, are in many cases found transferring 
themselves to the new quarters provided. The natural enemies also of a plant 
will, as that plant is more and more widely sown, be placed in a more favourable 
position to live and multiply, and often will increase so enormously in number 
as to be a source of much dread to the agriculturist. If the farmer, glancing 
proudly across his spreading fields of wheat, presently sees, hovering over them, 
clouds of minute insects, dancing in the sunlight, and finds these to be innu- 
merable swarms of chinch bugs, hessian flies or similar foes, he must not 
consider it a special affliction of Providence, but the natural working of laws 
that have existed foruntold periods, Man, as he has spread from continent to 
continent, clearing and cultivating and subduing the earth, has carried with him 
not only his various animals, grains, flowers, fruits and vegetables, but has con- 
tinuaily borne along, or been steadily followed by, many of his natural insect 
foes. Long lists could be given of insects which have been introduced into this 
country from Europe. One instance may be noticed, because the insect was 
brought but recently into Canada, and is known to all of you—I refer to Pieris 
rape, the cabbage butterfly. This, the common white butterfly—of which 
numbers were secn at several of our excursions—is easily distinguished from our 
native white by the black spots on its wings and the yellowish tint of the under- 
surface, It is about twenty years since it was first brought to Quebec—probably 
in the egg state on cabbage leaves—and its descendants have since destroyed 
millions of cabbages. The fiist one was captured in Quebec in 1859; ten years 
later it had occupied a large portion of the Middle States ; in 1875 it reached the 
western part of this province; two years ago I found it common in the most 
eastern portion of Nova Scotia, and its range is steadily widening west and 
south; last year it was reported common in Alabama and beyond Ohio, and 
wherever cabbages can grow this lover of them may be expected to find its way. 
It is impossible to estimate the extent of the loss inflicted by them, but, in cne 
year, they destroyed, in the neighbourhood of Quebec, over 250,000 head of 
cabbage. ‘Those of you who cultivate this vegetable in your gardens must have 
observed that, of late, these butterflies have not been so numerous as in forme 
years, and you may have wondered why it should be so; well, it is to the efforts 
of a very small ichneumon fly, called Pteromalus puparum, that the diminution in 
their numbers is due. This little fly, the natural foe of the butterfly, has, in 
some unknown way, followed it here from Europe, and has since multiplied so 
greatly as to be a powerful check upon the increase of the butterflies, The female 
ichneumon deposits her eggs in the chrysalis, which, if opened some time after- 
ward, will be found occupied by some fifty small grubs; and at least half the 
chrysalids examined will be found in this condition. 
In contemplating the loss and annoyance caused by insects, people too 
readily overlook the benefits derived from them—benefits so numerous that I 
shall mention only the chief one. They are the scavengers of nature, removing 
quietly and quickly all decaying animal and vegetable matter, and thus purifying 
both the air and the water. I will not weary you by entering further this 
evening into the great and varied claims that Entomology, as a study, has upon 
us, whether we consider the beauty or the grotesqueness of colour or ornamenta- 
tion of some species; the social instincts and surprising intelligence of such as 
bees and ants; the curious and often complex habitations of many; the meta- 
morphoses undergone; the products with which they furnish us; the wonderful 
instruments, such as stings, which they possess; or a multitude of equally 
important points, we find scope for the exercise of the highest powers of the 
intellect, and material can be gathered near at hand to give employment through- 
out a lifetime, and I trust that some among my hearers may be tempted to look 
more carcfully and fully into the strange and admirable phases of insect life, by 
