1932 ] 
The Olfactory Responses of Blowflies 
145 
THE EFFECT OF TEMPERATURE AND RELATIVE 
HUMIDITY UPON THE OLFACTORY RESPONSES 
OF BLOWFLIES 
By Cyril E. Abbott 
Morgan Park, 111. 
Introduction 
It appears that almost no effort has been made to deter- 
mine the possible conditioning of insect olfaction by other 
external factors. This may be due to the fact that studies 
in the relation of these factors to insect metabolism are 
comparatively recent. In 1917 Headlee discovered that at- 
mospheric moisture, through its relation to the water op- 
timum of the insect body, directly affects development. In 
the same year Hamilton found that above 20° C soil insects 
are especially sensitive to evaporation. Shelford (1913) 
observed that insects resisted drying more effectively that 
most other animals. Beattie (1928) has made some inter- 
esting experiments with Calliphora erythrocephala. She 
finds that a relative humidity of 70 is optimum for the spe- 
cies, and that saturated or dry air lowers the thermal death 
point. Miller (1930) finds that at 37.5° C the percentage 
of surviving adult Mexican bean beetles, irrespective of hu- 
midity, is high. At 42.5° C the percentage is low at all 
humidities, while at temperatures between the extremes, 
the greatest percent of survival is at a relative humidity 
of 73. Marchand (1920) observes that Blatta, Chionea and 
various species of mosquitoes orient to heat. According to 
Herter (1923) Formica rufa distinguishes temperature 
changes as low as *4° C. Miller and Gan were able to make 
Cremastog aster lineolata orient to radiant heat. Lodge 
(1918) finds that Musca domestica has its feeding reactions 
affected by changes in temperature and humidity. 
