HABITS OF THE ADULT FLY 57 



is of the opinion, therefore, that marked flies are likely 

 to be abnormal and are not fit for purposes of exact 

 experimentation. He found that it was impossible to 

 clip off the wing extremity and not inconvenience the 

 flight. 



On this subject of marking, Mr. J. P. Jepson, of 

 Cambridge, England, conducted some interesting ex- 

 periments during July and August, 1908, under the di- 

 rection of Professor Nuttall. He first tried ordinary 

 household flour, but the flies soon rid themselves of it. 

 This substance was used on account of the observation 

 that flies seen in mills often seem quite white in color. 

 Rice starch powder was next tried, with no success. 

 They were finally marked with ordinary colored black- 

 board chalks which were finely ground up in a mortar 

 and dusted on the flies until they were completely cov- 

 ered. They tried to clean themselves, beginning with 

 the eyes, but never succeeded in removing the chalk 

 from the upper portion of the thorax or from the base 

 of the wings. Further experiments were tried with 

 aniline dyes either made in the form of a powder with 

 rice starch or mixed with alcohol in the form of a 

 spray. Then again shellac was mixed with the alcohol 

 in order to make the color sticky. In his summary 

 he found that the use of various aniline dyes did not 

 prove satisfactory; with fuchsine the mortality was 

 very large. He found that dusting with rice starch 

 powder and then spraying with shellac and alcohol give 

 an excellent color, but decided that the flies must be 

 allowed to clean their eyes before spraying and that 



