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IXSECTS IX THEIR RELATION TO AGRICULTURE. 
By D. L. Van Dine. 
(Lecture II, Feb. 28th, 1908.) 
This is the second of two lectures delivered by Mr. Van Dine 
and illustrated by lantern slides, before the students of the College 
of Agriculture and Mechanic Arts of Hawaii. 
In my first lecture I trust I left with you an impression that 
insects are, as a class, wonderfully specialized and meeting their 
necessities for life and growth with marvelous adaptations. Such 
an impression will be an incentive to take up their study. You 
have formed, probably, a more definite idea of what an insect is. 
We distinguish birds from fishes for the reason that we know 
them, we are familiar with them and in the same way we can 
become familiar with insects and distinguish them from other 
members of the animal kingdom. You can be told that a spider 
is not an insect and you could remember and be able to repeat, 
if asked, that a spider is not an insect but a near relative. The 
better way is to determine in your own mind by observation and 
by the aid of books, just what an insect is. You will then know 
without being told, that a spider is not an insect. Do not, how- 
ever, allow the fact that insects do possess certain common 
physiological characters, separating them zoologically from other 
animals, blind you to the more important fact that they are in 
their life and habits intimately related to and dependent for their 
very existence on both the plant and animal world that surrounds 
them. 
Insects in their relation to man have been classified as follows : 
Insects are injurious: 
As destroyers of crops and other valuable plant life. 
As destroyers of stored foods, dwellings, clothes, books, etc. 
As injuring live stock and other useful animals. 
As annoying man. 
As carriers of disease. 
Insects are beneficial : 
As destroyers of injurious insects. 
As destroyers of noxious plants. 
As pollenizers of plants. 
As scavengers. 
As makers of soil. 
As food (both for man, for poultry, song birds, and food fishes) 
and as clothing, and as used in the arts. 
Insects in feeding upon plant life are simply fulfilling their 
part in the subjection of the plant world. They may be injurious 
or they may not, in accordance with the value to man of the plant 
