MODIFICATION OF COLOR. 



169 



In these experiments 10.8 per cent died in the larval stage, 46.1 per cent in 

 the pupal, and 43.1 per cent completed their transformation. Of the latter 

 there was about an equal division as regards sex, there being 51.5 per cent 

 males and 48.5 per cent females. The size and form were normal. 



In the shape, position, and fusions of the spots the color pattern was un- 

 modified ; but the size of the spots or the amount of dark color was increased 

 so that as regards general color there was a slight shifting of the modal con- 

 dition. This is shown in the following table, which gives the conditions of 

 the parent generations and those of the material used in experimentation and 

 in the control : 



Table 45- General color of beetles used. 



Empirical mode of parents 9 



Empirical mode of control 10 



Empirical mode in experiment . . 12 



Modal deviation of parents o 



Modal deviation of control -p- 1 



Modal deviation in experiment. . +3 



In all of these experiments there was a slight histonic skewness of from 

 one to four classes in each separate lot of individuals experimented upon, the 

 average being three classes. The skewness is histonic in this case toward a 

 more melanic condition, such as characterizes the ancestor of this beetle, 

 L. mnltitcvniata. 



Experiment 2. To determine the effect of a considerable increase in temperature upon 

 the color and color pattern of L. decemlineata. 



Conditions. Temperature on an average 9.767 C. above that in nature. 

 Other conditions normal. 



Apparatus. Glass cages and special breeding tanks warmed by the sun or 

 by artificial heat, and protected from radiation at night. 



In this experiment, in which are combined the data and results of many 

 experiments extending from 1893 to 1904, 7,800 larvae taken at random from 

 potato fields were used. These were all placed in the conditions of the ex- 

 periment in the last larval instar before the beginning of the prepupal period. 

 Food, moisture, light, soil, and other conditions were kept normal, the tem- 

 perature only being varied. The temperature records are as follows : 



Table 46. Temperature conditions. 



