172 



COI.ORATION IN LEPTINOTARSA. 



In this experiment, which extended over the years 1895 to 1903, 6,000 

 larvae were used, taken at random in the last instar. In the earlier experi- 

 ments, those covering the years 1895 to 1898, an ice box was used; and in the 

 later ones the special tanks. Food, moisture, light, and other conditions were 

 kept normal. The temperature records are as follows : 





Table 



SO. — Temperature conditions. 







Conditions — 



7 a. m. 



I p.m. 



8 p. m. 



Maxi- 

 mum. 



Mini- 

 mum. 



Aver- 

 age. 



Deviation 



from 

 normal. 



In nature 



In experiment . 



19.2 

 14.306 



°C. 



30.62 

 18.409 



17-389 

 15 



°C. 

 33-5 

 23.5 



13 

 12 



°C. 

 22.403 

 15.903 





 -6.5 



In these experiments 4 per cent died in the larval stage, 6 per cent in the 

 pupal, and 90 per cent appeared as imagines. In size these were normal, or 

 slightly larger than normal. The average duration of pupal life was 

 increased one and a half days. The color and color pattern were m.odified 

 as follows : The hypodermal color became a more intense yellow, often with 

 a reddish tinge; the cuticula color became a dense black, and all the areas 

 thereof were slightly increased in size, which gave the specimens a more 

 melanic appearance, as is shown in the following table of their seriations : 



Tabi,!: 51. — General color of beetles used. 



Class 



5 



6 



7 



8 



9 



10 



II 



12 



13 



14 



15 



16 



Parents 



Control 



Experiment . 



Ret. 



I 



P.ct. 

 2 

 2 



P.ct. 



5 



7 



I 



P.ct. 



20 



10 



2 



P.ct. 

 42 



23 

 3 



P.ct. 



18 



30 



7 



p.ct. 



9 

 16 

 12 



P.ct. 

 2 



6 

 22 



P.ct. 



I 



5 

 39 



P.ct. 



I 

 10 



P.ct. 

 3 



Ret. 



I 



Empirical mode of parents 9 



Empirical mode of control 10 



Empirical mode in experiment.. . 13 



Modal deviation of parents. ...... o 



Modal deviation of control -f-i 



M-odal deviation in experiment. . . 4-3 



A striking parallel exists between the seriations of this experiment and 

 those of experiment i in that the conditions of both act as a stimulus toward 

 an increase in the amount of pigmentation, and hence toward a more general 

 melanic appearance. 



Experiment 5. — To determine the effect of a considerably decreased average temper- 

 ature upon the color and color pattern of L. decemlineata. 



Conditions. — Temperature on the average 9.5° C. below that in nature, 

 with other conditions normal. 



Apparatus. — ^The same as in experiment 4. 



