12 MASS. EXPERIMENT STATION BULLETIN 261 



deposited was in proportion to the hours of exposure at 32°, showing that 

 very little development of the eggs, if any, occurred at the lower temperature. 



The stimulating effect of a varied temperature over a constant one is well 

 illustrated by comparing the actual number of eggs found with the expected 

 result. The fact that a varied temperature is more stimulating to develop- 

 mental processes than a constant one is not new to science, but very few 

 papers can he found which actually give data that demonstrate this. This 

 conclusion shows that results obtained from constant temperature studies are 

 inaccurate when compared with field conditions, but not necessarily imprac- 

 tical, as a great deal of information can be gained from such studies with a 

 large saving in time, labor, and equipment. 



Results were obtained from varied temperature environments about 27° 

 with high humidity only (Table II, 27°). The stinuilation to heavy egg pro- 

 duction caused by varied temperature conditions is readily seen. The expected 

 egg yield was not reached in one test, the 27°-22° combination. This result 

 is probably not significant as the actual number of eggs laid in all other 

 varied environments in the table exceeded the calculated results. The yield 

 was markedly reduced when the beetles were exposed to 32° for 16 hours. 



Varied temperature environments about 22° were much more complete than 

 at 27° (Table II, 22°). Heavy egg laying resulted in all combinations of 

 temperature above 17°. The large number of eggs (25 per cent more than 

 was expected) produced in the 22°-27° condition was much greater than with 

 any other set of teii.peratures and suggests that the optimum temperature is 

 somewhere between 22° and 27°. The reduction in the number of eggs laid 

 at a constant temperature of 22° with 40 per cent humidity was offset under 

 varied temperature conditions above 22°. The wide range of humidity that 

 was suitable for good egg production at 27° was equally satisfactory at 22° 

 in combination with higher temperatures. 



In Table I the minimum effective temperature was shown to be near 17°. 

 When 17° was combined with higher temperatures good egg yields that ex- 

 ceeded expectations were found (Table II, 17°). It is evident that the bean 

 beetle is capable of producing a sufficient number of eggs to maintain itself 

 in numbers at low temperature between 17° and 22°, even when the humidity 

 is below .50 per cent. 



Canstant and l^oried Environments. The effects of temperature and 

 moisture on the oviposition rate in both constant and varied environments can 

 be further illustrated by plotting the data in Tables I and II (fig. 1). The 

 figures represent the average numiber of eggs deposited per week in the va- 

 rious environments. More data are needed to determine accurately the limits 

 in the low temperature and low humidity regions. However, general conclu- 

 sions can be drawn from the data. Three zones are shown in the figure. The 

 area marked "Zone F' probably covers the combinations of temperature and 

 moisture in which the bean beetle is capable of producing a sufficient number 

 of eggs to maintain itself in economic numbers, as far as egg production is 

 concerned. Zone II represents the region where the insect jirobably will 

 maintain itself, but not in economic nxmibers; while Zone III covers the con- 

 ditions in which it will seldom be found. Keeping the lieetles in variable 

 environments enlarged the range of suitable temperature and moisture com- 

 binations over that obtained from constant conditions; but the results were 

 essentially the same in other respects. The suitable temperature range for 



