34 



Experimental Zoology 



Pictet has also tried the effects of insufficient nourishment, 

 using smaller amounts of the normal food. In the case of 

 Pieris crataegi, lack of food during the last days of the life of 

 the caterpillar causes the wings to become lighter in color and 

 more transparent. If all food is removed from the full-grown 



12 



14 



15 



FIG. 5. Psiluria monacha: typical male, Fig. IO; and female, Fig. n. Aber- 

 rant form P. ingra : male, Fig. 12; female, Fig. 13. Aberrant form P. eremita : 

 male, Fig. 14; female, Fig. 15. (After Pictet.) 



caterpillar of Vanessa urticae, it becomes a chrysalid in a few 

 days after the last moult. The butterflies are dwarfs, but show 

 no changes in coloration. On the other hand, if the very young 

 caterpillars are kept on a regime that becomes less sufficient 

 every day, they become pupae even before the last moult, and 

 produce dwarf butterflies that have the aberrant characters 

 much accentuated. 



