29 



the dependency of ''economic" upon ''scientific" entomology. 

 In attacking a problem from this point of view, the first thing 

 to be done is to correctly identify the species of the pest in ques- 

 tion, to study its geographical distribution, and to judge of the 

 most likely locality for its original habitat. Thus we are de- 

 pendent upon the work of the systematist, and require his very 

 best wm-k. Had a wrong determination been acted upon in the 

 case oPPefAnsiella saccharicida, Messrs. Perkins and Koebele 

 might have proceeded to some other part of the world from 

 which they did, and their efforts might not have been crowned 

 with the success that they were. 



Another case, now historic, which will demonstrate this 

 point, is that of Ceratitis capitata. Several entomologists 

 searched in various parts of the world for natural enemies of 

 this world-wide pest, and it was given out by more than one 

 that none existed ; not one of them visited that region which the 

 study of the systematic position of the insect, and the geograph- 

 ical distribution of the genus, indicated to be its natural habi- 

 tat. The fact that both Xorth and South Africa suffered from 

 the ravages of this fly turned people's attention away from any 

 other portion of that continent; the presence of natural land 

 barriers between these two places and Central West Africa be- 

 ing forgotten. Mr. W. M. Giffard, when organizing the expe- 

 dition last year, on behalf of the Board of Agriculture and 

 Forestry, took these facts into consideration, and we know the 

 success attending Professor Silvestri's researches. 



The time is now passed for discussing the value of parasites 

 in controlling insect pests, or whether parasites do control the 

 increase of their hosts; success has demonstrated that, under 

 certain conditions, the value of parasites is very great. That all 

 cases of insect ravages cannot be controlled by this means is best 

 recognized by those engaged in such work. That this method 

 cannot be greatly extended is due to our ignorance, and we shall 

 never attain to the success possible until our knowledge of m- 

 sect biology, systematics and geographical distribution is very 

 much greater than it is at present. It would be easy to state 

 cases where wrong identifications have made the center of dis- 

 tribution of a genus appear to be in one hemisphere whilst, in 

 truth, it is in the other. 



These considerations show how "practical" entomologists 

 are dependent upon the work of their ''scientific" brethren, and 

 how they require the very best work that can be given them. 



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