MODIFICATION 01' COLOR. 



195 



Experiments with Temperature and Moisture Both Variable. 



In nature the deviation of one environmental factor alone is of rare occur- 

 rence, for when one factor is changed, as, for example, temperature, a corre- 

 lated modification also occurs in others. Thus, in nature, if the temperature 

 in a given environment is lowered, the percentage of relative humidity is 

 increased, evaporation is decreased, the sensible temperature is altered, winds 



Text-ficuke 15. To illustrate the results obtained through theuseof moisture 

 as a stimulus, showing almost identical results to those obtained by the use 

 of temperature as a stimulus. Compare with text-figures 11 and 12. 



due to convection may start, and thus many changes follow from a slight alter- 

 ation in one environmental factor. Hence, in an investigation of environ- 

 mental influences, the results of changes in entire complexes must be studied 

 and interpreted. In the following section are given the results obtained from 

 experiments in which various groups of factors were changed. 



Experiments in which Temperature and Relative Humidity Vary Together 

 in the Same Direction Above or Below the Normal. 



Experiment 23. To determine the effects of a moderately increased average deviation 

 in both temperature and moisture upon the color and color pattern of L- decemlineata. 



Conditions. Temperature 6 C. and relative humidity 10 per cent on the 

 average above that in nature, with other conditions normal. 



Apparatus. Glass breeding tanks specially constructed. 



In these experiments, which were conducted during the years 1899 to 1904, 

 3,700 eggs were placed in the cages within a few hours after being laid. From 

 these 3,000 larvas were obtained, which were subjected to the following con- 

 ditions : 



