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other insects which are carnivorous instead of herbivorous in their 
feeding habits. Under artificial conditions induced by cultivation the 
balance of Nature becomes disturbed. Agricidtural operations largely 
consist in planting certain plants to the exclusion of others, over 
continuous areas of country. The insects which live at the expense of 
these plants are thus provided with conditions eminently favourable to 
their excessive multiplication, and become pests to the agriculturalist. 
The result is that the efficacy of the normal controlling factors of these 
insects becomes greatly reduced. Man has to step in and devise 
methods to take their place. It is the aim and function of applied 
entomology to investigate the habits and life-histories of all noxious 
insects. The ultimate object of such woi’k is to provide the requisite 
knowledge upon which to base those remedial or preventive measures 
which are likely to be effective in each specific case. 
The agricultural pests of this country do not cause less financial 
loss in proportion to the area under cultivation than in any other 
country. We have the advantage in England that no extensive areas 
of country are devoted to the cultivation of single crops to the exclusion 
of others. It is these conditions that offer unlimited facilities for the 
multiplication of the insects subsisting thereon, and have led to the 
vast problems that have to be faced in America, India, and other lands. 
If we were in possession of an adequate knowledge of the chief insects 
affecting English agriculture, the work of successfully combating them 
would make more rapid progress. I can see no valid reason why the 
damage they commit should not ultimately be reduced to an almost 
negligible quantity. It is essential to make an exact study of the life- 
history and biology of each individual species of injurious insects from 
every point of view. It is further necessary to study its seasonal 
occurrence, its distribution abroad, its parasites and the insects and 
other animals that are co-existent with it within the same area. The 
frequent failure of the measures recommended to combat insects in this 
country is more often than not traceable to lack of knowledge of the 
economy of the particular species being dealt with. Kieffer has called 
attention to a remarkable fact in a Cecidomyiid, Diplosis tritici, which 
attacks the grains of wheat. One of the measures advised, namely, 
burning the debris after threshing, has only an injurious effect. While 
it is true that this debris contains pupae of the Diplosis it is noteworthy 
that the healthy and non-parasitised larvae of these flies transform 
beneath the soil, while those which remain in the heads are, on the 
contrary, parasitised (Marchal, 1907, pp. 14-15). Miss Embleton 
