February, ’24] 
PETERSON: CHEMOTROPISM OF HYLEMYIA 
89 
The flies of Hylemyia antiqua Meig., and Hylemyia cilicrura Rond, 
have the habit of flying low and near the ground. When resting they 
are found on the ground or on low vegetation. The traps used were 
suited to this ground habit of the flies. The point of entrance for the 
flies into the trap was a narrow slit (hi to ^ inch wide) about the entire 
bottom between the tin base and the wire-screen cage. The flies of 
both species are attracted to light, positively phototropic, and they 
also have the habit of crawling upward. The upward crawling habit 
may be due to positive phototropism. After the flies were once below 
the rounded cone they usually fed on the bait and then in flying away 
from the bait they usually came to rest on the inner portion of the cone. 
They then crawled upward and through the small round hole at the top 
of the cone. Once within the upper part of the cage they did not escape. 
The cages were examined at different time intervals depending upon 
the nature of the experiment. In some cases 12 or 24 hours apart and 
in other instances as many as 7 days apart. It was found that 75 to 
100 cages was the maximum number one man could properly handle in 
one day. Whenever the cages were examined for the results of the 
experiments, the total number of adults of Hylemyia antiqua Meig. 
and Hylemyia cilicrura Rond., were counted and properly recorded and 
then the flies were removed at once. By proper shading with a dark 
cloth and inverting the detachable cone of the cage the flies were in¬ 
duced to enter small glass bottles where they were killed with chloro¬ 
form. After they were dead all of the Diptera found in one cage were 
placed in small tin pill boxes and carefully labeled with an accession 
number and date of collection. The flies were kept in the tin boxes in a 
dry place free of museum pests until the author had time to determine 
definitely the species and sex of each. Flies have been kept in this 
way for almost a year and they have been satisfactory for determination. 
The majority of the flies in the cages proved to be adults of Hylemyia 
antiqua Meig., and Hylemyia cilicrura Rond., during the period of this 
investigation. 
In making use of numerous concentrated oils and solutions that are 
highly odoriferous it was necessary to use some medium for diluting 
them. Several products were tried such as water, water solutions of 
several sugars, (cane, brown, maltose, lactose and dextrose), corn syrup 
(“Karo,” brown and white), molasses and honey. In all the experi¬ 
ments where a medium was used a check was included to determine the 
attractiveness of the medium by itself. In some respects corn syrup 
proved to be the most satisfactory medium. It has little or no attrac- 
