and it seems that one could hardly expect appreciable results before four or five years.
But what does this matter in any event? since we are trying to obtain a result of indefinite duration which will bring about exemption from the ruinous methods of destruction by insecticides and which will mark the end of a public calamity menacing the trees of the whole United States.
General Considerations and Conclusions
The exposition of facts we have presented in this memoir allows us to take stock of the importance gained during these recent years by the method of utilizing beneficial forms. It can not be denied that, practised in a judicious manner, it can render very great services, and the initiative of governments which have been encouraging large experiments destined to show its value, must be applauded. It would be bad taste indeed to criticize those who have brought about a check, for it is only by trying experiments that one can understand the conditions which may prevent success, and far from implying failure under such conditions, the experiments almost always teach a useful lesson.
Those accustomed to the experimental method and to laboratory research know well how the discovery of a new fact in science is made at the price of much groping, of misconceptions and of failures, and how these have to be conquered before the truth is learned. Is it reasonable, then, to suppose that it can be otherwise for these great experiments in economic entomology, of which we have just spoken? And if by forced circumstances those who are carrying them on can not be protected by the silence which the learned men of the laboratory enjoy, if the work which they are undertaking is exposed to distortion or exploitation by persons anxious to boast and to give out sensational information. . . these are circumstances which, to our eyes, can only add to their merit and to increase the rights which they have to our esteem.
If eulogy without reserve should be given to those who have taken part in this great movement in favor of the utilization of beneficial insects, we would have the right, on the other hand, to discuss the too-exclusive and too-optimistic conclusions to which some of the most fervent adherents of the method have been led.
It is in California above all, and in Australia, as we have said, that the theory has been formulated in the most absolute way. According to the claims of the State Board of Horticulture, of California, no insect is in its original home a pest of sufficient gravity to menace a crop in a serious way, because nature has always placed by its side a parasite capable of holding it in check. Each time that a new enemy reveals itself in a region and begins to undergo exaggerated multi-
