So much of the writings about insects must necessarily deal with their destructiveness that we may be in danger of forgetting that many insects have beneficial attributes and habits, the value of which we can hardly over estimate. It is a little startling to discover that this humble class of animals contributes to the world's commerce, products that sell for more than $ 125,000,000 each year, in the United States alone.
In this we see an important reason for studying these creatures very carefully, in order that we may be able to distinguish insect friend from insect enemy. Almost any entomologist can tell from his own experience of incidents where farmers have gone to great trouble and expense to destroy quantities of insects, only to learn later that the insect destroyed was not only harmless but was actually engaged in saving his crops by eating the destructive form.
Each citizen owes it to himself to know, as well as possible, the sundry ways in which beneficial insects affect, to his advantage, the complex currents of plant and animal life.
Buried in the archives of entomological literature is a wealth of fascinating facts and rich observation that is for ever lost to all but a few, unless brought together and simplified to meet the demands of busy, modern readers. To anyone who knows the field of entomology and the extent of its literature it need not be explained that no man is capable of a comprehensive acquaintance with all of its many phases.
The first ten chapters of Destructive and Useful Insects have been completely revised and brought up-to-date and much new material has been added. Also considerable new material has been added to chapters VIII, IX and X.