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 
