February, '15] FERNALD: NEEDS IN ECONOMIC ENTOMOLOGY 



35 



Insect outbreaks and their causes are as yet entirely without ex- 

 planation except in such general terms as to leave us as uncertain when 

 to expect them and how to prevent or prepare to meet them as before. 

 We guess they may be due to climatic conditions beyond our control 

 or perhaps to an unusual absence of the natural enemies of the insects 

 concerned. I- find practically no evidence on the subject, however^ 

 and if climatic conditions are involved we lack any knowledge as to 

 what these are. We need pioneers to explore this field and can only 

 hope that some day, even if they cannot tell us how to prevent the 

 outbreaks, they may discover the principles involved and be able to 

 warn us of those soon to come. When the entomologist can publish a 

 notice that the army worm, for example, will appear in destructive 

 abundance the coming summer, based on anything hke definite cer- 

 tainty, we may consider ourselves as having made a long forward step 

 in the progress of the science to which we are devoting our lives. 

 Whether this can ever become possible is after all aside from the point. 

 We must explore the field and find out. Personally, taking the prog- 

 ress of entomology in the past as a criterion, I believe the time will 

 come when the causes of outbreaks will be thoroughly understood and 

 their times predicted with nearly as great accuracy as is now done for 

 the weather. 



The possibihty of the successful introduction and spread of insect 

 diseases through the agency of man has been given some attention 

 for quite a long time. Thus far the results can hardly be called en- 

 couraging, for though disease is often very effective, man's relation 

 to it appears to have been quite unimportant, the factors determining 

 success seemingly having been beyond his control. Whether this will 

 always be the case, or whether the introduction of new methods of 

 work and distribution may place this field in the list of those which 

 can be profitably tilled, can only be learned by further research. It 

 is to be hoped, therefore, that workers in this line may continue their 

 investigations until its possibilities have been fully demonstrated. 



Factors which influence the distribution of animals and plants have 

 been given considerable attention by zoologists and botanists, at 

 least since the appearance of Wallace's two classic volumes on ''The 

 Geographical Distribution of Animals." In all the literature on this 

 subject, however, little consideration has been given to insects. Pass- 

 ing references, allusions to the presence of different forms in the differ- 

 ent life zones, and general statements make up the bulk of published 

 information about insects in this field. So far as I can learn, no argu- 

 ment bearing on crop raising has ever been provided from this source 

 of information. The publications of the Bureau of Biological Survey 

 list the mammals, birds and other vertebrates, and the plants of the 



