194 



COI^ORATION IN LEPTINOTARSA. 

 Table 86. — Humidity conditions. 



Humidity— 



7 a. m. 



10 a. m. 



I p. m. 



3P-in. 



8 p. m. 



Maxi- 

 niura. 



Mini- 

 mum. 



Aver- 

 age. 



Deviation 



from 



normal. 



In nature 



In experiment.. 



Per ct. 

 lOO 



45 



Per ct. 

 65 

 35 



Per ct. 



50 

 20 



Per ct. 



55 

 30 



Per ct. 



100 



40 



Per ct. 

 100 



55 



Per ct. 



43 

 10 



Per ct. 

 74 



34 



Per ct. 

 

 -40 



In these experiments 93 per cent died in the larval stage, 6.6 per cent in the 

 pupal, and 0.4 per cent emerged. All stages were highly albinic, and the 

 imagines extremely so, as is shown in the following table : 



Table 87. — General color of beetles used. 



Class 



I 

 P.ct. 



2 

 P.ct. 



3 

 P.ct. 



4 

 P.ct. 



5 

 P.ct. 



6 

 P.ct. 



7 



P.ct. 



8 

 P.ct. 



9 



P.ct. 



10 

 P.ct. 



It 



p.ct. 



12 

 P.ct. 



13 



P.ct. 





Parents 











I 



2 



s 



20 



42 



18 



q 



2 



I 



Control 



. . 









2 



7 



8 



17 



37 



iq 



8 



I 



I 



Experiment*. 



5 



17 



3 



I 













' 



•• 





•• 



* Individuals = 26. 



Empirical mode of parents 9 



Empirical mode of control. ....... 9 



Empirical mode in experiment 2 



Modal deviation of parents .... o 



Modal deviation of control o 



Modal deviation in experiment. . — 7 



In this series of experiments the hypodermal color was a pure, translucent 

 white without any development of lipochrome pigments ; all the dark mark- 

 ings were lighter in color and many w^ere entirely wanting. 



The general results derived from these humidity experiments have been 

 put into text-figure 15. It is apparent from a study of these records that 

 the results of experiments with deviations of humidity are almost exactly the 

 same as those which were obtained from experiments with deviations of tem- 

 perature. Such deviations from the normal, either toward an increase or a 

 decrease, produce up to a maximumi increased pigmentation and a consequent 

 melanic tendency, but beyond this the effect is reversed, pigmentation is re- 

 tarded, and the tendency toward albinism becomes more and more pronounced 

 as the deviation from the normal becomes greater. These results are well 

 shown in text-figures 11 to 15. Neither temperature nor humidity seems to 

 have any specific influence upon the coloration of this beetle ; but each acts as 

 a stimulus toward the production of an increase in activity under slight devia- 

 tions, and toward a decrease under larger deviations; and the curve of the 

 response is similar to that obtained from very many physiological experiments. 



