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THE BEARING OF PHYSIOLOGY ON ECONOMIC 

 ENTOMOLOGY.* 



By J. Dewitz, Ph.D., 



Director of the Entomological Research Laboratory of the Konigliche Lehranstalt, 



Geisenheim, Germany. 



The progress of applied Entomology is mainly visible in the discovery of 

 practical means for the destruction of insects injurious to cultivated plants, and 

 in the minute determination of the various stages of the growth and development 

 of such insects. More recently the parasites of insect pests, both of vegetable 

 and animal origin, have also largely attracted attention. But physiological 

 research, so far as injurious insects are concerned, has almost entirely been over- 

 looked and neglected ; although this line of enquiry affords obvious opportunities 

 for arriving at the very essence of the whole matter, and should indeed be made 

 one of the main starting points in the study of insect pests. 



In such circumstances it may be interesting to show how the study of phy- 

 siology bears in a remarkable way on several questions of entomological research 

 to which I have devoted special attention. 



The Tropisms. 



Whereas the study of tropisms in Botany is nothing new, it is only of recent 

 date as regards animals. So far as I have been able to ascertain, the earliest 

 published communications on tropisms in animals were those of authors who 

 occupied themselves with the chemotropism of leucocytes, and these were 

 followed by the investigations of Hermann 23 and myself. 4 While I found and 

 described for the first time the reaction of animals to contact (later authors 

 called it stereotropism), Hermann discovered electrotropism in his experiments 

 on tadpoles. 



The form of tropism which interests us most here is phototropism, from which 

 has originated the long established method of catching and destroying injurious 

 insects by means of artificial light. The modest beginning of the method may 

 be traced back as far as 1787, when the Abbe Roberjot, parish priest of St. 

 Verand,near Macon, systematically caught the vine moths, Sparganothis pillerianaj 

 by means of lighted candles placed on the window-sills of his house and of wood 

 fires in the vineyards. Since then insect trap-lanterns have been gradually 

 developed and improved with the progress of science and industry, until we find 

 to-day the most perfected modern acetylene lamps almost everywhere, and in the 

 vineyards of the Champagne (France) even most complicated electrical installa- 

 tions, specially designed for catching and destroying injurious insects. But 

 although the trap-lantern, so far as its exterior aspect and construction are con- 

 cerned, has been brought to high perfection, the method itself has so far been 

 treated almost in a wholly empirical manner. Much labour and thought have 

 been devoted to the perfecting of the trap-lantern method, and much has been 



* This article has been kindly translated for me by Mr. F. Clotten, of London. 

 f [Mr. J. H. Durrant informs me that the generic name Oenophthira, used by the author, is 

 no longer recognised by Microlepidopterists — Ed.] 



(27226—2.) Wt. PI 1—21. 1000. 12/12. D & S. 



