124 



NOTES ON CHEMOTROPISM IN THE HOUSE-FLY. 



By E. R. SPEYER. 



The experiments described in this paper were carried out under the 

 auspices of the Bureau of Entomology, United States Department of 

 Agriculture, at Washington in 1914. 



Acknowledgments are due to the Bureau for permission to publish 

 these notes, and to Dr L. 0. Howard, Mr W. D. Hunter, to the Bureau 

 of Chemistry and the Institute of Chemical Research, for much valuable 

 assistance in making the records. 



In its original form, this paper embodied a Synopsis and Review of 

 literature upon Chemotropism in Insects up to the year 1914, but it 

 has been decided to omit these, in view of the existence of at least one 

 publication dealing with the literature, and of other important work 

 done by Entomologists since these notes were written. 



It may be explained here that the terms Positive and Negative 

 Chemotropism are applied respectively to substances which exert a 

 definite attraction and a definite repulsion to the insects mentioned. 



SECTION I. 



PRELIMINARY EXPERIMENTS UPON THE ATTRACTION OF THE 

 HOUSE-FLY BY COMMON FOOD-STUFFS. 



(a) Type of trap used. 



In all these and future experiments here described, the No. 1 Gal- 

 vanized "Perfect" Fly-Trap (to be obtained from the Ludlow-Saylor 

 Wire Co., St Louis, Missouri) was employed. It is about 2 feet 6 inches 

 high, 8 inches in diameter at base, composed of wire gauze supported 

 by three metal strips, and fitted with a metal lid. At the base of the 

 trap is an inverted wire cone with a rim of supporting metal. This rim 

 fits closely within a corresponding ring on the outside wire, to which 

 it can be fixed by means of three screws. At the top of the cone is a 

 small hole which admits the insects into the trap. The bait is placed 

 in a dish beneath the wire cone. 



