6 MASS. EXPERIMENT STATION BULLETIN 261 



made of glass so that the light intensity could be controlled from outside the 

 cabinet. The doors, which were about two feet square, contained glass so 

 that the insects and instruments could be observed without opening the com- 

 partments. The temperature was maintained with electrical heating units 

 operated with thermostats, and cold running water, the two working against 

 each other. Relative humidity was controlled by placing saturated salt solu- 

 tions in wide pans, so as to have a large amount of surface exposed. In order 

 to secure uniform conditions, fans were used to keep the air in motion. The 

 fans were placed so that the air passed directly over the salt solutions. The 

 experimental material was placed on wire shelves at about the middle of the 

 compartment so that the air currents were directed through them, thus expos- 

 ing the contents to the surrounding environment. 



Environmental Conditions Obtained. 



Temperature of any degree desired could be obtained, but relative humidity 

 much below 32 per cent could not be secured. Generally a salt could be found 

 that would give the approximate humidity sought above 32 per cent to nearly 

 saturation of the atmosphere. All temperature records are in degrees centi- 

 grade, and moisture data in percentage of relative humidity. 



These experiments were conducted as a part of the Mexican bean beetle 

 project of the "VA'yoming Agricultural Experiment Station. Since the en- 

 vironments were controlled, the effects of temperature and moisture on the 

 insect could not have been due to any geographical peculiarity in Wyoming. 



Series of temperatures ranging from 17° to 37° at intervals of 5° were used. 

 Moisture conditions varying from 32 to 93 per cent were maintained in the 

 various temperature environments. Since it is impossible to discuss the effects 

 of temperature on the Mexican bean beetle without taking into consideration 

 the influence of moisture, the reactions of the insect to both factors are con- 

 sidered jointly. 



Experiments xvith Adults. 



Constant Conditions. A temperature of 37° was foimd to be above the 

 maximum effective temperature regardless of the humidity that was main- 

 tained in the cabinets. Death resulted in every case in less than forty-eight 

 hours, and the majority were killed in less than twenty-four hours (Table I, 

 37°). It is evident that the temperature alone was the major factor in de- 

 struction in this case, as death occurred in all humidity conditions used. 



When a constant temperature of 32° was maintained, very interesting re- 

 sults were secured, as the interaction of both temperature and moisture are 

 evident (Table I, 32°). Heavy egg production occurred in the dry environ- 

 ment, while the yield was exceedingly low in the moist conditions. The in- 

 hibitory action of a high himiidity on oviposition was evident, as laying beetles 

 in 92 per cent himiidity discontinued deposition in the second week and all 

 but one female was dead by the end of the third week. Non-laying beetles 

 in 90 per cent humidity were not stimulated to cg^ production and all were 

 dead by the end of the third week. All of the beetles were living at the end 

 of five weeks in 32 per cent humidity. An earlier series with humidities of 

 40, 70, and 90 per cent gave results showing the same tendencies, but the data 

 are not included in the table since the food was not kept fresh and starvation 

 may have influenced the results in the dry environment. The amount of food 

 consumed in 70 per cent humidity was much reduced, while very little food 



