146 
Psyche 
[ December 
The following study was suggested by Kennedy's (1927) 
statement that the olfactory powers of certain Hymenop- 
tera appear to vary with relative humidity. Under normal 
conditions, adults of Lucilia sericata Meig. react to ethyl 
butyrate by an extension of the proboscis and regurgitation 
of fluid (Fig. 1). This is a definite feeding response to ol- 
factory stimulation. The problem was to determine to what 
extent this response is dependent upon temperature and 
relative humidity. 
Fig. 1. Extension of proboscis and regurgitation 
by Lucilia sericata. 
Materials and Methods 
Adult flies were kept in small cages and fed a solution 
of cane sugar and what juices they could obtain from hog’s 
liver. The latter was replaced every alternate day, and any 
eggs removed to flower pots about two-thirds full of sand. 
These containers were covered with muslin. The maggots 
pupated in the sand and as soon as adult flies began to 
emerge in a given container, the latter was transferred to 
one of the cages. 
Flies were tested individually and discarded after each 
test. The insect was placed in a chamber consisting of a test 
tube fitted with a rubber stopper having two inlet tubes. 
During the test, this tube was kept in a constant tempera- 
ture bath composed of an aquarium fitted with two Lolag 
heaters, a thermostat, a stirring device, and two U-tubes 
which served to equalize the temperature of the air drawn 
into the fly chamber. One of these tubes was connected 
with the “check” apparatus; the other with the “test” ap- 
paratus. When properly adjusted, the temperature of the 
